Chapter 29 Development and Inheritance Lecture Presentation by

Chapter 29 Development and Inheritance Lecture Presentation by

Chapter 29 Development and Inheritance Lecture Presentation by Lee Ann Frederick University of Texas at Arlington 2015 Pearson Education, Inc. An Introduction to Development and Inheritance Learning Outcomes 29-1 Explain the relationship between differentiation and development, and specify the various stages of development. 29-2 Describe the process of fertilization, and

explain how developmental processes are regulated. 29-3 List the three stages of prenatal development, and describe the major events of each. 2015 Pearson Education, Inc. An Introduction to Development and Inheritance Learning Outcomes 29-4 Explain how the three germ layers are involved in forming the extraembryonic membranes, and discuss the importance of the placenta as an endocrine organ. 29-5 Describe the interplay between the maternal

organ systems and the developing fetus, and discuss the structural and functional changes in the uterus during gestation. 2015 Pearson Education, Inc. An Introduction to Development and Inheritance Learning Outcomes 29-6 List and discuss the events that occur during labor and delivery. 29-7 Identify the features and physiological changes of the postnatal stages of life. 29-8 Relate basic principles of genetics to the inheritance of human traits. 2015 Pearson Education, Inc.

An Introduction to Development and Inheritance Development Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity Inheritance Transfer of genetic material from generation to generation 2015 Pearson Education, Inc. 29-1 Development Differentiation Creation of different types of cells required in development Occurs through selective changes in genetic

activity As development proceeds, some genes are turned off, others are turned on Fertilization Also called conception When development begins 2015 Pearson Education, Inc. 29-1 Development Embryonic Development Occurs during first two months after fertilization Study of these events is called embryology Fetal Development Begins at start of ninth week Continues until birth

2015 Pearson Education, Inc. 29-1 Development Prenatal Development Embryonic and fetal development stages Postnatal Development Commences at birth Continues to maturity, the state of full development or completed growth 2015 Pearson Education, Inc. 29-1 Development Inheritance Transfer of genetically determined characteristics from generation to generation

Genetics Study of mechanisms responsible for inheritance 2015 Pearson Education, Inc. 29-2 Fertilization Fertilization Fusion of two haploid gametes, each containing 23 chromosomes Produces zygote containing 46 chromosomes Spermatozoon Delivers paternal chromosomes to fertilization site Travels relatively large distance Is small, efficient, and highly streamlined 2015 Pearson Education, Inc.

29-2 Fertilization Gamete Provides: Cellular organelles Inclusions Nourishment Genetic programming necessary to support development of embryo for a week 2015 Pearson Education, Inc. 29-2 Fertilization

Fertilization Occurs in uterine tube within a day after ovulation Secondary oocyte travels a few centimeters Spermatozoa must cover distance between vagina and ampulla Capacitation Must occur before spermatozoa can fertilize secondary oocyte Contact with secretions of seminal glands Exposure to conditions in female reproductive tract 2015 Pearson Education, Inc. 29-2 Fertilization Hyaluronidase Enzyme breaks down bonds between adjacent follicle cells Allows spermatozoon to reach oocyte

Acrosin Is a proteolytic enzyme Is required to reach oocyte 2015 Pearson Education, Inc. 29-2 Fertilization Acrosomes Release hyaluronidase and acrosin Penetrate corona radiata, zona pellucida, toward oocyte surface Oocyte Activation Contact and fusion of cell membranes of sperm and oocyte Follows fertilization Oocyte completes meiosis II, becomes mature

ovum 2015 Pearson Education, Inc. 29-2 Fertilization Polyspermy Fertilization by more than one sperm Prevented by cortical reaction Cortical Reaction Releases enzymes that: Inactivate sperm receptors Harden zona pellucida 2015 Pearson Education, Inc. 29-2 Fertilization Female Pronucleus

Nuclear material remaining in ovum after oocyte activation Male Pronucleus Swollen nucleus of spermatozoon Migrates to center of cell 2015 Pearson Education, Inc. 29-2 Fertilization Amphimixis Fusion of female pronucleus and male pronucleus Moment of conception

Cell becomes a zygote with 46 chromosomes Fertilization is complete 2015 Pearson Education, Inc. 29-2 Fertilization Cleavage Series of cell divisions Produces daughter cells Differentiation Involves changes in genetic activity of some cells but not others 2015 Pearson Education, Inc. Figure 29-1a Fertilization.

300 a 2015 Pearson Education, Inc. A secondary oocyte and numerous sperm at the time of fertilization. Notice the difference in size between the gametes. Figure 29-1b Fertilization (Part 1 of 6). Oocyte at Ovulation Ovulation releases a secondary oocyte and the first polar body; both are surrounded by the corona radiata. The oocyte is suspended in metaphase of meiosis II. Corona

radiata Zona pellucida 2015 Pearson Education, Inc. First polar body Figure 29-1b Fertilization (Part 2 of 6). 1 Fertilization and Oocyte Activation Acrosomal enzymes from multiple sperm create gaps in the corona radiata. A single sperm then makes

contact with the oocyte membrane, and membrane fusion occurs, triggering oocyte activation and the completion of meiosis. Fertilizing spermatozoon 2015 Pearson Education, Inc. Second polar body Figure 29-1b Fertilization (Part 3 of 6). 2 Pronucleus Formation Begins The sperm is absorbed into the

cytoplasm, and the female pronucleus develops. Nucleus of fertilizing spermatozoon 2015 Pearson Education, Inc. Female pronucleus Figure 29-1b Fertilization (Part 4 of 6). 3 Spindle Formation and Cleavage Preparation

The male pronucleus develops, and spindle fibers appear in preparation for the first cleavage division. Male pronucleus 2015 Pearson Education, Inc. Female pronucleus Figure 29-1b Fertilization (Part 5 of 6). 4 Amphimixis Occurs and Cleavage Begins

Metaphase of first cleavage division 2015 Pearson Education, Inc. Figure 29-1b Fertilization (Part 6 of 6). 5 Cleavage Begins The first cleavage division nears completion about 30 hours after fertilization. Blastomeres 2015 Pearson Education, Inc.

29-3 Gestation Induction Cells release chemical substances that affect differentiation of other embryonic cells Can control highly complex processes Gestation Time spent in prenatal development Consists of three integrated trimesters, each three months long 2015 Pearson Education, Inc. 29-3 Gestation 1. First Trimester Period of embryonic and early fetal development Rudiments of all major organ systems appear

2. Second Trimester Development of organs and organ systems Body shape and proportions change 3. Third Trimester Rapid fetal growth and deposition of adipose tissue Most major organ systems are fully functional 2015 Pearson Education, Inc. 29-4 The First Trimester First Trimester Includes four major stages 1. 2. 3. 4.

2015 Pearson Education, Inc. Cleavage Implantation Placentation Embryogenesis 29-4 The First Trimester Cleavage Sequence of cell divisions begins immediately after fertilization Zygote becomes a pre-embryo, which develops into multicellular blastocyst Ends when blastocyst contacts uterine wall Implantation Begins with attachment of blastocyst to endometrium of uterus

Sets stage for formation of vital embryonic structures 2015 Pearson Education, Inc. 29-4 The First Trimester Placentation Occurs as blood vessels form around periphery of blastocyst and placenta develops Embryogenesis Formation of viable embryo Establishes foundations for all major organ systems 2015 Pearson Education, Inc. 29-4 The First Trimester The First Trimester

Most dangerous period in prenatal life 40 percent of conceptions produce embryos that survive past first trimester 2015 Pearson Education, Inc. 29-4 The First Trimester Cleavage and Blastocyst Formation Blastomeres Identical cells produced by cleavage divisions Morula Stage after three days of cleavage Pre-embryo is solid ball of cells resembling mulberry Reaches uterus on day 4 2015 Pearson Education, Inc.

29-4 The First Trimester Cleavage and Blastocyst Formation Blastocyst Formed by blastomeres Hollow ball with an inner cavity Known as blastocoele 2015 Pearson Education, Inc. 29-4 The First Trimester Cleavage and Blastocyst Formation Trophoblast Outer layer of cells separate outside world from blastocoele Cells responsible for providing nutrients to developing embryo

2015 Pearson Education, Inc. 29-4 The First Trimester Cleavage and Blastocyst Formation Inner cell mass Clustered at end of blastocyst Exposed to blastocoele Insulated from contact with outside environment by trophoblast Will later form embryo 2015 Pearson Education, Inc. Figure 29-2 Cleavage and Blastocyst Formation (Part 1 of 2). Blastomeres Polar

bodies 4-cell stage 2-cell stage DAY 1 First cleavage division DAY 0: Fertilization 2015 Pearson Education, Inc. DAY 2 Figure 29-2 Cleavage and Blastocyst Formation (Part 2 of 2).

Zona pellucida Early morula DAY 3 DAY 4 Advanced morula Hatching Inner cell mass DAY 6 Blastocoele

Days 710: Implantation in uterine wall (see Figure 293) 2015 Pearson Education, Inc. Trophoblast Blastocyst 29-4 The First Trimester Implantation Occurs seven days after fertilization Blastocyst adheres to uterine lining Trophoblast cells divide rapidly, creating several layers 2015 Pearson Education, Inc.

29-4 The First Trimester Implantation Cellular trophoblast Cells closest to interior of blastocyst Syncytial trophoblast Outer layer Erodes path through uterine epithelium by secreting hyaluronidase 2015 Pearson Education, Inc. Figure 29-3 Stages in Implantation (Part 1 of 2). DAY 6 FUNCTIONAL ZONE

OF ENDOMETRIUM UTERINE CAVITY Uterine glands Blastocyst DAY 7 Trophoblast Blastocoele Inner cell mass

2015 Pearson Education, Inc. Figure 29-3 Stages in Implantation (Part 2 of 2). DAY 8 Endometrial capillary Syncytial trophoblast Cellular trophoblast DAY 9 Developing villi Amniotic cavity

Lacuna 2015 Pearson Education, Inc. 29-4 The First Trimester Ectopic Pregnancy Implantation occurs outside uterus Does not produce viable embryo Can be life threatening Lacunae Trophoblastic channels carrying maternal blood 2015 Pearson Education, Inc. 29-4 The First Trimester Formation of the Amniotic Cavity Villi extend away from trophoblast into

endometrium Increase in size and complexity until day 21 Amniotic Cavity A fluid-filled chamber Inner cell mass is organized into an oval sheet two layers thick Superficial layer faces amniotic cavity Deeper layer is exposed to fluid contents of blastocoele 2015 Pearson Education, Inc. 29-4 The First Trimester Gastrulation and Germ Layer Formation Formation of third layer of cells Cells in specific areas of surface move toward central line

Known as primitive streak 2015 Pearson Education, Inc. 29-4 The First Trimester Primitive Streak Migrating cells leave surface and move between two layers Creates three distinct embryonic layers, or germ layers 1. Ectoderm: consists of the superficial cells that did not migrate into interior of inner cell mass 2. Endoderm: consists of cells that face blastocoele 3. Mesoderm: consists of poorly organized layer of migrating cells between ectoderm and endoderm

2015 Pearson Education, Inc. 29-4 The First Trimester Ectodermal Contributions Integumentary system: Epidermis, hair follicles and hairs, nails, and glands communicating with the skin (sweat glands, mammary glands, and sebaceous glands) Skeletal system: Pharyngeal cartilages and their derivatives in adults (portion of sphenoid, the auditory ossicles, the styloid processes of the temporal bones, the cornu and superior rim of the hyoid bone) Nervous system: All neural tissue, including brain and spinal cord 2015 Pearson Education, Inc.

29-4 The First Trimester Ectodermal Contributions Endocrine system: Pituitary gland and adrenal medullae Respiratory system: Mucous epithelium of nasal passageways Digestive system: Mucous epithelium of mouth and anus, salivary glands 2015 Pearson Education, Inc. 29-4 The First Trimester Mesodermal Contributions Integumentary system:

Dermis and hypodermis Skeletal system: All components except some pharyngeal derivatives Muscular system: All components 2015 Pearson Education, Inc. 29-4 The First Trimester Mesodermal Contributions Endocrine system: Adrenal cortex, endocrine tissues of heart, kidneys, and gonads Cardiovascular system:

All components 2015 Pearson Education, Inc. 29-4 The First Trimester Mesodermal Contributions Lymphatic system: All components Urinary system: The kidneys, including the nephrons and the initial portions of the collecting system Reproductive system: The gonads and the adjacent portions of the duct systems Miscellaneous:

The lining of the body cavities (pleural, pericardial, and peritoneal) and the connective tissues that support all organ systems 2015 Pearson Education, Inc. 29-4 The First Trimester Endodermal Contributions Endocrine system: Thymus, thyroid gland, and pancreas Respiratory system: Respiratory epithelium (except nasal passageways) and associated mucous glands Digestive system: Mucous epithelium (except mouth and anus), exocrine glands (except salivary glands), liver, and pancreas

2015 Pearson Education, Inc. 29-4 The First Trimester Endodermal Contributions Urinary system: Urinary bladder and distal portions of the duct system Reproductive system: Distal portions of the duct system, stem cells that produce gametes 2015 Pearson Education, Inc. 29-4 The First Trimester Embryonic Disc Oval, three-layered sheet

Produced by gastrulation Will form body of embryo Rest of blastocyst will be involved in forming extraembryonic membranes 2015 Pearson Education, Inc. Figure 29-4 The Inner Cell Mass and Gastrulation (Part 1 of 2). Day 10: Yolk Sac Formation While cells from the superficial layer of the inner cell mass migrate around the amniotic cavity, forming the amnion, cells from the deeper layer migrate around the outer edges of the blastocoele. This is the first step in the formation of the yolk sac, a second extraembryonic membrane. For about the next two weeks, the

yolk sac is the primary nutrient source for the inner cell mass; Superficial layer it absorbs and distributes nutrients released into the blastocoele by the trophoblast. Deep layer 2015 Pearson Education, Inc. Syncytial trophoblast Cellular trophoblast Blastocoele Amniotic cavity Yolk sac Lacunae

Figure 29-4 The Inner Cell Mass and Gastrulation (Part 2 of 2). Day 12: Gastrulation By day 12, superficial cells of the blastodisc have begun to migrate toward a central line known as the primitive streak. At the primitive streak, the migrating cells leave the surface and move between the two existing layers. This movement creates three distinct embryonic layers: (1) the ectoderm, consisting of superficial cells that did not migrate into the interior of the blastodisc; (2) the endoderm, consisting of the cells that face the yolk sac; and (3) the mesoderm, consisting of the poorly organized layer of migrating cells between the ectoderm and the endoderm. Collectively, these three embryonic layers are called germ layers, and the migration process is called gastrulation. Gastrulation produces an oval,

three-layered sheet known as the embryonic disc. This disc will form the body of the embryo, whereas all other cells of the blastocyst will be part of the extraembryonic membranes. 2015 Pearson Education, Inc. Yolk sac Amnion Germ Layers Ectoderm Mesoderm Primitive streak Blastodisc Endoderm Embryonic disc

29-4 The First Trimester Formation of the Extraembryonic Membranes Support embryonic and fetal development Yolk sac Amnion Allantois Chorion 2015 Pearson Education, Inc. 29-4 The First Trimester The Yolk Sac

Begins as layer of cells spread out around outer edges of blastocoele to form complete pouch Important site of blood cell formation 2015 Pearson Education, Inc. 29-4 The First Trimester The Amnion Combination of mesoderm and ectoderm Ectodermal layer enlarges and cells spread over inner surface of amniotic cavity Mesodermal cells create outer layer Continues to enlarge through development Amniotic fluid Surrounds and cushions developing embryo or fetus 2015 Pearson Education, Inc.

29-4 The First Trimester The Allantois Sac of endoderm and mesoderm Base later gives rise to urinary bladder The Chorion Combination of mesoderm and trophoblast Blood vessels develop within mesoderm Rapid-transit system for nutrients that links embryo with trophoblast First step in creation of functional placenta 2015 Pearson Education, Inc. 29-4 The First Trimester Chorionic Villi In contact with maternal tissues

Create intricate network within endometrium carrying maternal blood 2015 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 3 of 7). 1 Week 2 Migration of mesoderm around the inner surface of the cellular trophoblast forms the chorion. Mesodermal migration around the outside of the amniotic cavity, between the ectodermal cells and the trophoblast, forms the amnion. Mesodermal migration around the

endodermal pouch creates the yolk sac. Chorion Mesoderm Blastocoele 2015 Pearson Education, Inc. Cellular trophoblast Amnion Yolk sac Syncytial trophoblast Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 4 of 7).

2 Week 3 The embryonic disc bulges into the amniotic cavity at the head fold. The allantois, an endodermal extension surrounded by mesoderm, extends toward the trophoblast. Head fold of embryo Amniotic cavity (containing amniotic fluid) Extraembryonic

membranes Amnion Allantois Yolk sac Chorion Chorionic villi Syncytial of placenta trophoblast 2015 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 5 of 7). 3 Week 4 The embryo now has a head fold and a tail fold. Constriction of

the connections between the embryo and the surrounding trophoblast narrows the yolk stalk and body stalk. Tail fold Embryonic gut 2015 Pearson Education, Inc. Embryonic head fold Body stalk Yolk

stalk Yolk sac Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 6 of 7). 4 Week 5 The developing embryo and extraembryonic membranes bulge into the uterine cavity. The trophoblast pushing out into the uterine cavity remains covered by endometrium but no longer participates in nutrient absorption and embryo support. The embryo moves away from the placenta, and the body stalk and yolk stalk

fuse to form an umbilical stalk. Uterus Myometrium Decidua basalis Umbilical stalk Placenta Yolk sac Chorionic villi of placenta Decidua capsularis

Decidua parietalis Uterine cavity 2015 Pearson Education, Inc. Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 7 of 7). 5 Week 10 The amnion has expanded greatly, filling the uterine cavity. The fetus is connected to the placenta by an elongated umbilical cord that contains a portion of the allantois, blood vessels, and the remnants of the yolk stalk. Decidua parietalis

Umbilical cord Decidua basalis Placenta Amnion Amniotic cavity Decidua capsularis 2015 Pearson Education, Inc. Chorion 29-4 The First Trimester

Placentation Body stalk Connection between embryo and chorion Contains distal portions of allantois and blood vessels that carry blood to and from placenta Yolk stalk Narrow connection between endoderm of embryo and yolk sac 2015 Pearson Education, Inc. 29-4 The First Trimester Decidua Capsularis Thin portion of endometrium No longer participates in nutrient exchange and chorionic villi in region disappear

Decidua Basalis Disc-shaped area in deepest portion of endometrium Where placental functions are concentrated Decidua Parietalis Rest of the uterine endometrium No contact with chorion 2015 Pearson Education, Inc. 29-4 The First Trimester Umbilical Cord Connects fetus and placenta Contains allantois, placental blood vessels, and yolk stalk Placental Circulation Through paired umbilical arteries

Returns in single umbilical vein 2015 Pearson Education, Inc. Figure 29-6a Views of Placental Structures (Part 1 of 3). Decidua capsularis Amnion Umbilical cord (cut) Placenta Chorion

Yolk sac Decidua basalis a A view of the uterus after the fetus has been removed and the umbilical cord cut. Arrows in the enlarged view indicate the direction of blood flow. Blood flows into the placenta through ruptured maternal arteries and then flows around chorionic villi, which contain fetal blood vessels. 2015 Pearson Education, Inc. Figure 29-6a Views of Placental Structures (Part 2 of 3). Decidua parietalis

Myometrium Uterine cavity Cervical (mucous) plug in cervical canal External os Cervix Vagina a A view of the uterus after the fetus has been 2015 Pearson Education, Inc.

removed and the umbilical cord cut. Arrows in the enlarged view indicate the direction of blood flow. Blood flows into the placenta through ruptured maternal arteries and then flows around chorionic villi, which contain fetal blood vessels. Figure 29-6a Views of Placental Structures (Part 3 of 3). Chorionic villi Umbilical vein Umbilical arteries Area filled with maternal blood

Amnion Trophoblast (cellular and syncytial layers) a 2015 Pearson Education, Inc. Maternal blood vessels A view of the uterus after the fetus has been removed and the umbilical cord cut. Arrows in the enlarged view indicate the direction of blood flow. Blood flows into the placenta through ruptured maternal arteries and then flows around chorionic villi, which contain fetal blood vessels. Figure 29-6b Views of Placental Structures.

Syncytial trophoblast Embryonic connective tissue Area filled with maternal blood Fetal blood vessels Chorionic villus b 2015 Pearson Education, Inc.

LM 280 A cross section through a chorionic villus, showing the syncytial trophoblast exposed to the maternal blood space. 29-4 The First Trimester The Endocrine Placenta Synthesized by syncytial trophoblast, released into maternal bloodstream Human chorionic gonadotropin (hCG)

Human placental lactogen (hPL) Placental prolactin Relaxin Progesterone Estrogens 2015 Pearson Education, Inc. 29-4 The First Trimester Human Chorionic Gonadotropin (hCG) Appears in maternal bloodstream soon after implantation Provides reliable indication of pregnancy Pregnancy ends if absent 2015 Pearson Education, Inc. 29-4 The First Trimester

Human Placental Lactogen (hPL) Prepares mammary glands for milk production Synergistic with growth hormone at other tissues Ensures adequate glucose and protein is available for the fetus Placental Prolactin Helps convert mammary glands to active status 2015 Pearson Education, Inc. 29-4 The First Trimester Relaxin A peptide hormone secreted by placenta and corpus luteum during pregnancy Increases flexibility of pubic symphysis, permitting pelvis to expand during delivery Causes dilation of cervix

Suppresses release of oxytocin by hypothalamus and delays labor contractions 2015 Pearson Education, Inc. 29-4 The First Trimester Embryogenesis Body of embryo begins to separate from embryonic disc Body of embryo and internal organs start to form Folding and differential growth of embryonic disc produce bulge that projects into amniotic cavity Projections are head fold and tail fold Organogenesis Process of organ formation 2015 Pearson Education, Inc.

Figure 29-7a The First 12 Weeks of Development. Future head of embryo Thickened neural plate (will form brain) Axis of future spinal cord Somites Neural folds Cut wall of amniotic cavity Future tail of embryo a Week 2. An SEM of the superior surface of a monkey

embryo at 2 weeks of development. A human embryo at this stage would look essentially the same. 2015 Pearson Education, Inc. Figure 29-7b The First 12 Weeks of Development. Medulla oblongata Ear Pharyngeal arches Forebrain Eye Heart Somites

Body stalk Arm bud Tail Leg bud b Week 4. Fiber-optic view of human development at week 4 (about 5 mm in size). 2015 Pearson Education, Inc. Figure 29-7c The First 12 Weeks of Development. Chorionic

villi Amnion Umbilical cord Placenta c Week 8. Fiber-optic view of human development at week 8 (about 1.6 cm in size). 2015 Pearson Education, Inc. Figure 29-7d The First 12 Weeks of Development. Amnion Umbilical cord

d Week 12. Fiber-optic view of human development at week 12 (about 5.4 cm in size). 2015 Pearson Education, Inc. 29-5 The Second and Third Trimesters Second Trimester Fetus grows faster than surrounding placenta Third Trimester Most of the organ systems become ready Growth rate starts to slow

Largest weight gain Fetus and enlarged uterus displace many of mothers abdominal organs 2015 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development (Part 1 of 4). 2015 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development (Part 2 of 4). 2015 Pearson Education, Inc. Table 29-2 An Overview of Prenatal Development (Part 3 of 4). 2015 Pearson Education, Inc.

Table 29-2 An Overview of Prenatal Development (Part 4 of 4). 2015 Pearson Education, Inc. Figure 29-8a The Second and Third Trimesters. a 2015 Pearson Education, Inc. A four-month-old fetus, seen through a fiber-optic endoscope (about 13.3 cm in size) Figure 29-8b The Second and Third Trimesters. b

2015 Pearson Education, Inc. Head of a six-monthold fetus, revealed through ultrasound (about 30 cm in size) Figure 29-9a Growth of the Uterus and Fetus. Placenta Uterus Umbilical cord Amniotic fluid Cervix Fetus at

16 weeks Vagina a Pregnancy at 16 weeks, showing the positions of the uterus, fetus, and placenta. 2015 Pearson Education, Inc. Figure 29-9b Growth of the Uterus and Fetus. 9 months 8 months 7 months 6 months After dropping, in preparation

to delivery 5 months 4 months 3 months b Pregnancy at three months to nine months (full term), showing the superior-most position of the uterus within the abdomen. 2015 Pearson Education, Inc. Figure 29-9c Growth of the Uterus and Fetus. Diaphragm Liver Stomach

Pancreas Transverse colon Small intestine Uterus Urinary bladder Pubic symphysis Vagina Urethra Rectum c A sectional view through the abdominopelvic cavity of a woman who is not pregnant. 2015 Pearson Education, Inc.

Figure 29-9d Growth of the Uterus and Fetus. Liver Stomach Pancreas Transverse colon Fundus of uterus Aorta Small intestine Umbilical cord Placenta Uterus

Common iliac vein Cervical (mucous) plug in cervical canal Urinary bladder External os Pubic symphysis Vagina Urethra Rectum d Pregnancy at full term. Note the positions of the uterus and full-term fetus within the abdomen, and the displacement of abdominal organs. 2015 Pearson Education, Inc.

29-5 The Second and Third Trimesters Pregnancy and Maternal Systems Developing fetus is totally dependent on maternal organ systems for nourishment, respiration, and waste removal Maternal adaptations include increases in: Respiratory rate and tidal volume Blood volume Nutrient and vitamin intake Glomerular filtration rate Size of uterus and mammary glands

2015 Pearson Education, Inc. 29-5 The Second and Third Trimesters Progesterone Released by placenta Has inhibitory effect on uterine smooth muscle Prevents extensive, powerful contractions Opposition to Progesterone Three major factors 1. Rising estrogen levels 2. Rising oxytocin levels 3. Prostaglandin production 2015 Pearson Education, Inc. 29-5 The Second and Third Trimesters Structural and Functional Changes in the Uterus

False labor Occasional spasms in uterine musculature Contractions not regular or persistent True labor Results from biochemical and mechanical factors Continues due to positive feedback Labor contractions Begin in myometrium 2015 Pearson Education, Inc. Figure 29-10 Factors Involved in the Initiation of Labor and Delivery. Placental Factors Fetal Factors

Placental estrogens increase the sensitivity of the smooth muscle cells of the myometrium and make contractions more likely. As delivery approaches, the production of estrogens accelerates. Estrogens also increase the sensitivity of smooth muscle fibers to oxytocin. Relaxin produced by the placenta relaxes the pelvic articulations and dilates the cervix. Growth and the increase in fetal weight stretches and distorts the myometrium.

Fetal pituitary releases oxytocin in response to estrogens. Distortion of Stretched Myometrium Distortion of the myometrium increases the sensitivity of the smooth muscle layers, promoting spontaneous contractions that get stronger and more frequent as the pregnancy advances. Maternal Oxytocin Release Maternal oxytocin release is stimulated by high estrogen levels and by distortion of the cervix.

Prostaglandin Production Estrogens and oxytocin stimulate the production of prostaglandins in the endometrium. These prostaglandins further stimulate smooth muscle contractions. Increased Excitability of the Myometrium Oxytocin and prostaglandins both stimulate the myometrium. In addition, the sensitivity of the uterus to oxytocin increases dramatically. The smooth muscle in a late-term uterus is 100 times more sensitive to oxytocin than the smooth muscle in a nonpregnant uterus. LABOR CONTRACTIONS OCCUR 2015 Pearson Education, Inc. Labor contractions move the fetus and further distort the myometrium. This

distortion stimulates additional oxytocin and prostaglandin release. This positive feedback continues until delivery is completed. 29-6 Labor Parturition Is forcible expulsion of fetus Contractions Begin near top of uterus, sweep in wave toward cervix Strong, occur at regular intervals, increase in force and frequency

Change position of fetus, move it toward cervical canal 2015 Pearson Education, Inc. 29-6 Labor Stages of Labor 1. 2. 3. Dilation stage Expulsion stage Placental stage 2015 Pearson Education, Inc. 29-6 Labor

Dilation Stage Begins with onset of true labor Cervix dilates Fetus begins to shift toward cervical canal Highly variable in length, but typically lasts over eight hours Frequency of contractions steadily increases Amniochorionic membrane ruptures (water breaks) 2015 Pearson Education, Inc. Figure 29-11 The Stages of Labor (Part 1 of 4).

Fully developed fetus before labor begins Pubic symphysis Placenta Vagina Umbilical cord 2015 Pearson Education, Inc. Sacral promontory Cervical canal Cervix

Figure 29-11 The Stages of Labor (Part 2 of 4). 1 2015 Pearson Education, Inc. The Dilation Stage 29-6 Labor Expulsion Stage Begins as cervix completes dilation Contractions reach maximum intensity Continues until fetus has emerged from vagina Typically less than two hours Delivery Arrival of newborn infant into outside world

2015 Pearson Education, Inc. 29-6 Labor Episiotomy Incision through perineal musculature Needed if vaginal canal is too small to pass fetus Repaired with sutures after delivery 2015 Pearson Education, Inc. 29-6 Labor Cesarean Section (C-section) Removal of infant by incision made through abdominal wall Opens uterus just enough to pass infants head Needed if complications arise during dilation or expulsion stages

2015 Pearson Education, Inc. Figure 29-11 The Stages of Labor (Part 3 of 4). 2 2015 Pearson Education, Inc. The Expulsion Stage 29-6 Labor Placental Stage Muscle tension builds in walls of partially empty uterus Tears connections between endometrium and placenta Ends within an hour of delivery with ejection of

placenta, or afterbirth Accompanied by a loss of blood 2015 Pearson Education, Inc. Figure 29-11 The Stages of Labor (Part 4 of 4). 3 The Placental Stage Uterus 2015 Pearson Education, Inc. Ejection of the placenta

29-6 Labor Premature Labor Occurs when true labor begins before fetus has completed normal development Newborns chances of surviving are directly related to body weight at delivery 2015 Pearson Education, Inc. 29-6 Labor Immature Delivery Refers to fetuses born at 2527 weeks of gestation Most die despite intensive neonatal care Survivors have high risk of developmental abnormalities Premature Delivery

Refers to birth at 2836 weeks Newborns have a good chance of surviving and developing normally 2015 Pearson Education, Inc. 29-6 Labor Difficult Deliveries Forceps delivery Needed when fetus faces mothers pubis instead of sacrum Risks to infant and mother are reduced if forceps are used Forceps resemble large, curved salad tongs Used to grasp head of fetus 2015 Pearson Education, Inc.

29-6 Labor Difficult Deliveries Breech birth Legs or buttocks of fetus enter vaginal canal first instead of head Umbilical cord can become constricted, cutting off placental blood flow Cervix may not dilate enough to pass head Prolongs delivery Subjects fetus to severe distress and potential injury 2015 Pearson Education, Inc. 29-6 Labor Multiple Births Dizygotic twins Also called fraternal twins

Develop when two separate oocytes were ovulated and subsequently fertilized Genetic makeup not identical 70 percent of twins 2015 Pearson Education, Inc. 29-6 Labor Multiple Births Monozygotic twins Also called identical twins Result either from: Separation of blastomeres early in cleavage Splitting of inner cell mass before gastrulation Genetic makeup is identical because both formed from same pair of gametes

2015 Pearson Education, Inc. 29-6 Labor Multiple Births Conjoined twins Siamese twins Genetically identical twins Occurs when splitting of blastomeres or of embryonic disc is not completed 2015 Pearson Education, Inc. 29-6 Labor Rates of Multiple Births Twins in 1 of every 89 births Triplets in 1 of every 892 (7921) births Quadruplets in 1 of every 893 (704,969) births

2015 Pearson Education, Inc. 29-7 Postnatal Life Five Life Stages 1. 2. 3. 4. 5. Neonatal period Infancy Childhood Adolescence Maturity 2015 Pearson Education, Inc.

29-7 Postnatal Life Duration of Life Stages Neonatal period: extends from birth to 1 month Infancy: 1 month to 2 years of age Childhood: 2 years until adolescence Adolescence: period of sexual and physical maturation Senescence: process of aging that begins at end of development (maturity) 2015 Pearson Education, Inc. 29-7 Postnatal Life

The Neonatal Period, Infancy, and Childhood Two major events occur 1. Organ systems become fully operational 2. Individual grows rapidly and body proportions change significantly Pediatrics Medical specialty focusing on postnatal development from infancy to adolescence 2015 Pearson Education, Inc. 29-7 Postnatal Life The Neonatal Period Transition from fetus to neonate Neonate Newborn

Systems begin functioning independently Respiratory Circulatory Digestive Urinary 2015 Pearson Education, Inc. 29-7 Postnatal Life Lactation and the Mammary Glands Colostrum Secretion from mammary glands Ingested by infant during first two to three days

Contains more proteins and less fat than breast milk Many proteins are antibodies that help ward off infections until immune system is functional Mucins present that inhibit replication of rotaviruses As production drops, mammary glands convert to milk production 2015 Pearson Education, Inc. 29-7 Postnatal Life Breast Milk Consists of water, proteins, amino acids, lipids, sugars, and salts Also contains large quantities of lysozymes enzymes with antibiotic properties Milk let-down reflex

Mammary gland secretion triggered when infant sucks on nipple Continues to function until weaning, typically one to two years 2015 Pearson Education, Inc. Figure 29-12 The Milk Let-Down Reflex. 3 Oxytocin Secretion The stimulation of tactile receptors in the nipple leads to the stimulation of secretory neurons in the paraventricular nucleus of the maternal hypothalamus. Posterior lobe of the

pituitary gland 4 5 Oxytocin Release The hypothalamic neurons release oxytocin into the posterior lobe of the pituitary gland. Oxytocin enters the bloodstream and is distributed throughout the body. Milk Ejected Circulating oxytocin reaches the mammary gland, causing the contraction of myoepithelial cells in

the walls of the lactiferous ducts and sinuses. The result is milk ejection, or milk let-down. Start 1 Stimulation of Tactile Receptors Mammary gland secretion is triggered when the infant sucks on the nipple. 2015 Pearson Education, Inc. 2 Neural Impulse Transmission Impulses are propagated to the spinal

cord and then to the brain. 29-7 Postnatal Life Infancy and Childhood Growth occurs under direction of circulating hormones Growth hormone Adrenal steroids Thyroid hormones Growth does not occur uniformly Body proportions gradually change 2015 Pearson Education, Inc. Figure 29-13 Growth and Changes in Body Form and Proportion (Part 1 of 2). Prenatal Development

Embryonic Development Fetal Development 4 weeks 8 weeks 16 weeks 2015 Pearson Education, Inc. Figure 29-13 Growth and Changes in Body Form and Proportion (Part 2 of 2). Postnatal Development Neonatal Childhood

Infancy Adolescence Maturity 5 ft 4 ft 3 ft 2 ft 1 ft 0 1 month 2015 Pearson Education, Inc.

1 year Puberty (between 914 years) 18 years 29-7 Postnatal Life Adolescence and Maturity Puberty is a period of sexual maturation and marks the beginning of adolescence Generally starts at age 12 in boys, age 11 in girls Three major hormonal events interact 1. Hypothalamus increases production of GnRH 2. Circulating levels of FSH and LH rise rapidly 3. Ovarian or testicular cells become more sensitive

to FSH and LH Hormonal changes produce sex-specific differences in structure and function of many systems 2015 Pearson Education, Inc. 29-7 Postnatal Life Adolescence Begins at puberty Continues until growth is completed Maturity (Senescence)

Aging Reduces functional capabilities of individual Affects homeostatic mechanisms Sex hormone levels decline at menopause or male climacteric 2015 Pearson Education, Inc. 29-7 Postnatal Life Geriatrics Medical specialty dealing with problems associated with aging Trained physicians, or geriatricians 2015 Pearson Education, Inc. 29-7 Postnatal Life Effects of Aging on Organ Systems

The characteristic physical and functional changes that are part of the aging process affect all organ systems Examples discussed in previous chapters include the following: A loss of elasticity in the skin that produces sagging and wrinkling (pp. 172173) A decline in the rate of bone deposition, leading to weak bones, and degenerative changes in joints that make them less mobile (pp. 199, 283) Reductions in muscular strength and ability (p. 377) 2015 Pearson Education, Inc. 29-7 Postnatal Life Effects of Aging on Organ Systems Examples discussed in previous chapters include the following: Impairment of coordination, memory, and

intellectual function (p. 557) Reductions in the production of, and sensitivity to, circulating hormones (p. 644646) Appearance of cardiovascular problems and a reduction in peripheral blood flow that can affect a variety of vital organs (p. 775) Reduced sensitivity and responsiveness of the immune system, leading to infection, cancer, or both (p. 825) 2015 Pearson Education, Inc. 29-7 Postnatal Life Effects of Aging on Organ Systems Examples discussed in previous chapters include the following: Reduced elasticity in the lungs, leading to decreased respiratory function (p. 873) Decreased peristalsis and muscle tone along the

digestive tract (p. 928) Decreased peristalsis and muscle tone in the urinary system, coupled with a reduction in the glomerular filtration rate (p. 928) Functional impairment of the reproductive system, which eventually becomes inactive when menopause or the male climacteric occurs (pp. 10881089) 2015 Pearson Education, Inc. 29-8 Inheritance Nucleated Somatic Cells Carry copies of original 46 chromosomes present in zygote Genotype Chromosomes and their component genes Contain unique instructions that determine anatomical and physiological characteristics Derived from genotypes of parents

Phenotype Physical expression of genotype Anatomical and physiological characteristics 2015 Pearson Education, Inc. 29-8 Inheritance Patterns of Inheritance Homologous chromosomes Members of each pair of chromosomes 23 pairs carried in every somatic cell At amphimixis, one member of each pair is contributed by spermatozoon, other by ovum 2015 Pearson Education, Inc. 29-8 Inheritance Patterns of Inheritance

Autosomal chromosomes 22 pairs of homologous chromosomes Most affect somatic characteristics Each chromosome in pair has same structure and carries genes that affect same traits 2015 Pearson Education, Inc. 29-8 Inheritance Patterns of Inheritance Sex chromosomes Last pair of chromosomes Determine whether individual is genetically male or female Karyotype Entire set of chromosomes

Locus Genes position on chromosome 2015 Pearson Education, Inc. Figure 29-14 A Human Male Karyotype. 2015 Pearson Education, Inc. 29-8 Inheritance Patterns of Inheritance Alleles are various forms of given gene Alternate forms determine precise effect of gene on phenotype Homozygous Both homologous chromosomes carry same allele of particular gene

Simple inheritance Phenotype determined by interactions between single pair of alleles 2015 Pearson Education, Inc. 29-8 Inheritance Interactions between Alleles Heterozygous Homologous chromosomes carry different allele of particular gene Resulting phenotype depends on nature of interaction between alleles Strict dominance Dominant allele expressed in phenotype, regardless of conflicting instructions carried by

other allele 2015 Pearson Education, Inc. 29-8 Inheritance Interactions between Alleles Recessive allele Expressed in phenotype only if same allele is present on both chromosomes of homologous pair Incomplete dominance Heterozygous alleles produce unique phenotype Codominance Exhibits both dominant and recessive phenotypes for traits 2015 Pearson Education, Inc.

Figure 29-15 Major Patterns of Inheritance (Part 1 of 2). Major Patterns of Inheritance Inheritance Involving Autosomal Chromosomes Inheritance Involving Sex Chromosomes Simple Inheritance Polygenic Inheritance The phenotype is determined by a single pair of alleles. Approximately 80% of your genotype falls within

this category. The phenotype is determined by interactions among the alleles of several genes. 2015 Pearson Education, Inc. Examples Hair color (other than blond or red, which are recessive traits) Skin color Eye color Height

Sex-linked inheritance involves genes on the sex chromosomes. Most examples involve the X chromosome. An X-linked allele determines the phenotype in males since there is no corresponding allele on the Y chromosome. Most known cases involve alleles that are recessive in females. Examples Redgreen color blindness Hemophilia (some forms) Duchennes muscular dystrophy Figure 29-15 Major Patterns of Inheritance (Part 2 of 2).

Major Patterns of Inheritance Inheritance Involving Autosomal Chromosomes Strict Dominance Codominance Incomplete Dominance One allele dominates the other allele and determines the phenotype Both alleles are expressed in the phenotype Two different alleles

produce intermediate traits in the phenotype Examples of dominant traits Examples of recessive traits

Normal skin pigmentation Freckles

Nearsightedness Farsightedness Astigmatism Free earlobes Tongue rolling Rh factor Type A or B blood Huntingtons disease 2015 Pearson Education, Inc. Albino pigmentation Absence of freckles Normal vision Attached earlobes Inability to roll tongue Rh factor absent Type O blood

Sickle cell anemia Cystic fibrosis TaySachs disease Phenylketonuria Examples Examples Type AB blood Structure of albumins Structure of transferrins

Hemoglobin A production Hemoglobin S production 29-8 Inheritance Penetrance and Expressivity Penetrance Percentage of individuals with particular genotype that show expected phenotype Expressivity Extent to which particular allele is expressed Teratogens Factors that result in abnormal development 2015 Pearson Education, Inc. 29-8 Inheritance

Predicting Inheritance Punnett square Simple box diagram used to predict characteristics of offspring Polygenic inheritance Involves interactions among alleles on several genes Cannot predict phenotypic characteristics using Punnett square Linked to risks of developing several important adult disorders 2015 Pearson Education, Inc. Figure 29-16a Predicting Phenotypic Characters by Using Punnett Squares. a

Maternal alleles (contributed by the ovum). Every ovum will carry the recessive gene a. a Paternal alleles (contributed by the spermatozoon). Every sperm produced by a homozygous dominant (AA) father will carry the A allele. A

Aa a Aa All have normal skin pigmentation A Aa Aa If the father is homozygous for normal pigmentation, all of the children will have the genotype Aa, and all will have normal skin pigmentation.

2015 Pearson Education, Inc. Figure 29-16b Predicting Phenotypic Characters by Using Punnett Squares. b a Half of the sperm produced by a heterozygous (Aa) father will carry the dominant allele A, and the other half will carry the recessive allele a. Aa

A a Maternal alleles a Aa 50% of the children are heterozygous and have normal pigmentation aa aa

50% of the children are homozygous recessive and exhibit albinism. If the father is heterozygous for normal skin pigmentation, the probability that a child will have normal pigmentation is reduced to 50%. 2015 Pearson Education, Inc. 29-8 Inheritance Predicting Inheritance Suppression One gene suppresses other Second gene has no effect on phenotype Complementary gene action Dominant alleles on two genes interact to produce

phenotype different from that seen when one gene contains recessive alleles 2015 Pearson Education, Inc. 29-8 Inheritance Sources of Individual Variation During meiosis, maternal and paternal chromosomes are randomly distributed Each gamete has unique combination of maternal and paternal chromosomes 2015 Pearson Education, Inc. 29-8 Inheritance Genetic Recombination During meiosis, various changes can occur in chromosome structure, producing gametes with

chromosomes that differ from those of each parent Greatly increases range of possible variation among gametes Can complicate tracing of inheritance of genetic disorders 2015 Pearson Education, Inc. 29-8 Inheritance Genetic Recombination Crossing over Parts of chromosomes become rearranged during synapsis When tetrads form, adjacent chromatids may overlap Translocation Reshuffling process

Chromatids may break, overlapping segments trade places 2015 Pearson Education, Inc. Figure 29-17 Crossing Over and Recombination. a Tetrad at synapsis Synapsis, with the formation of a tetrad during meiosis 2015 Pearson Education, Inc.

b Crossing over c Recombination Crossing over of portions of two homologous chromosomes The exchange of corresponding segments and groups of genes increases genetic variation among the gametes produced.

29-8 Inheritance Genetic Recombination Genomic imprinting During recombination, portions of chromosomes may break away and be deleted Effects depend on whether abnormal gamete is produced through oogenesis or spermatogenesis 2015 Pearson Education, Inc. 29-8 Inheritance Genetic Recombination Chromosomal abnormalities Damaged, broken, missing, or extra copies of chromosomes Few survive to full term Produce variety of serious clinical conditions

2015 Pearson Education, Inc. 29-8 Inheritance Mutation Changes in nucleotide sequence of allele Spontaneous mutations Result of random errors in DNA replication Errors relatively common, but in most cases error is detected and repaired by enzymes in nucleus Errors that go undetected and unrepaired have potential to change phenotype Can produce gametes that contain abnormal alleles 2015 Pearson Education, Inc. 29-8 Inheritance Carriers Individuals who are heterozygous for abnormal

allele but do not show effects of mutation 2015 Pearson Education, Inc. 29-8 Inheritance Sex-Linked Inheritance Sex Chromosomes X Chromosome Considerably larger than Y Has more genes than does Y chromosome Carried by all oocytes Y Chromosome Includes dominant alleles specifying that the individual will be male Not present in females 2015 Pearson Education, Inc.

29-8 Inheritance Sperm Carry either X or Y chromosome Because males have one of each, can pass along either X-Linked Genes that affect somatic structures Carried by X chromosome Inheritance does not follow pattern of alleles on autosomal chromosomes 2015 Pearson Education, Inc. Figure 29-18 Inheritance of an X-Linked Trait A womanwho has two X chromosomescan be either

homozygous dominant (XCXC) or heterozygous (XCXc) and still have normal color vision. She will be unable to distinguish reds from greens only if she carries two recessive alleles, XcXc. A man has only XC one X chromosome, so whichever allele that chromosome carries determines whether he has normal color vision or is redgreen color blind. Y

2015 Pearson Education, Inc. XC Xc XCXC XCXc Normal female Normal female (carrier) XCY XcY Normal male

Color-blind male 29-8 Inheritance The Human Genome Project and Beyond Goal was to transcribe entire human genome Has mapped thousands of human genes Genome Full complement of genetic material Karyotyping Determination of individuals complete chromosomal complement 2015 Pearson Education, Inc. Figure 29-19 A Map of Human Chromosomes.

Color Blindness (multiple forms) Chapter 17 Fragile-X Syndrome Chapter 29 Hemophilia Chapter 19 Prostate Cancer Chapter 28 Gauchers Disease Lysosomal storage disease caused by excess glycolipids in plasma membranes Neurofibromatosis, Type 2 Tumors of the auditory nerves and tissues surrounding the brain Familial Colon Cancer* Chapter 24 Downs Syndrome

Chapter 29 Retinitis Pigmentosa* Chapter 17 Amyotrophic Lateral Sclerosis* Chapter 15 Huntingtons Disease Chapter 17 ADA Deficiency An enzyme deficiency that affects the immune system Familial Polyposis of the Colon Abnormal tissue growths that commonly lead to colon cancer

Familial Hypercholesterolemia Extremely high cholesterol Myotonic Dystrophy Form of muscular dystrophy in which symptoms often develop after puberty Amyloidosis Accumulation of an insoluble fibrillar protein in the tissues Breast Cancer* Chapter 28 Y1 2 3 22 X 4 21

5 20 19 6 CHROMOSOME 18 7 PAIRS 17 8 16 9 10 15 14 13 12 11 Polycystic Kidney Disease Chapter 26

Spinocerebellar Ataxia Destroys neurons in the brain and spinal cord, resulting in loss of muscle control Cystic Fibrosis Chapter 23 Burkitts Lymphoma Cancer of lymphocytes; a type of non-Hodgkin lymphoma Retinitis Pigmentosa* Chapter 17 Epilepsy, progressive Chapter 14 TaySachs Disease Lysosomal storage disease affecting neural tissue

Malignant Melanoma Chapter 5 Marfans Syndrome Chapter 6 Ovarian Cancer Chapter 28 Alzheimers Disease* Chapter 16 Multiple Endocrine Neoplasia, Type 2 Tumors in endocrine glands and other tissues a1-Antitrypsin Deficiency

SCID Chapter 22 Causes a predisposition to develop emphysema Retinoblastoma A relatively common tumor of the eye, accounting for 2% of childhood malignancies Muscular Dystrophy Chapter 10 PKU (phenylketonuria) Chapter 25 Diabetes Mellitus, Type 1 Chapter 18 Sickle Cell Anemia Chapter 19

* One form of the disease 2015 Pearson Education, Inc.

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