Chapter 38

Chapter 38 - 38.1 Reflections on Sexual Reproduction Sexual Reproduction meiosis gametes zygote S e p a r a tio n int o s e x e s is c o s tly in t

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Unformatted text preview: 38.1 Reflections on Sexual Reproduction Sexual Reproduction: meiosis gametes zygote - S e p a r a tio n int o s e x e s is c o s tly in t e r m s of e n e r g y a n d r e s o ur c e s As e x u al Re pr o d u c tio n: sin gl e in divid u al p r o d u c e s id e n tic al offs prin g a si d e fro m m u t a tio n - Ph e n o t y pic u nifor mity e n s ur e s a d a p t a tio n 38.2 Stages of Reproduction and Development Overview of stages of animal reproduction and development - G a m e t e for m a tio n - Fertiliz a tio n s p e r m p e n e t r a t e s a m a t u r e e g g , fu sin g t o for m a zy g o t e - Cle a v a g e c ell divisio n s incr e a s e n u m b e r of c ells b u t n o t e g g's origin al v olu m e ; t h e c u t s pr o d u c e a bl a s t ul a wit h c ells c all e d bl a s t o m e r e s e n clo s e d b y a fluid-fille d c a vity c all e d t h e bl a s t o c o el - G a s t r ul a tio n ti m e of s t r u c t u r al or g a niz a tio n; bl a s t ul a u n d e r g o e s g a s t r ul a tio n; c ells b e c o m e a rr a n g e d int o a g a s t r ul a a n e a rly e m b r y o nic for m wit h t w o or t hr e e p ri m a r y tis s u e lay e r s ( lay e r s) o Ect o d e r m o u t e r m o s t p ri m a r y tis s u e ( e m e r g e s first); s o ur c e of n e r v o u s s y s t e m a n d o u t e p a r t of int e g u m e n t o End o d e r m inn er m o s t; s o ur c e of g u t's in n e r linin g a n d or g a n s d e riv e d fro m it o Me s o d e r m b e t w e e n o u t e r a n d in n e r p ri m a r y tis s u e lay e r s; giv e s ris e t o m u s cl e s, m o s t sk el e t o n, t o t h e circ ul a t ory, r e pr o d u c tiv e, a n d e x cr e t o ry s y s t e m s , a n d c o n n e c tiv e tis s u e s g u t a n d int e g u m e n t - Or g a n for m a tio n p ri m a r y tis s u e lay e r s a p p e a r a n d c ells b e c o m e di s tin c t s u b p o p ul a tio n s; n for mi n g c ells b e c o m e incr e a si n gly s p e ci aliz e d in s t r u c t ur e a n d fu n c tio n - Growt h a n d tis s u e s p e ci aliz a tio n o v e r ti m e , tis s u e s a n d or g a n s m a t u r e in siz e, s h a p e , pr o p a n d fu nc tio n; e x t e n d s t o a d ult h o o d 38.3 Early Marching Orders Sperm consists of only paternal DNA and bit of equipment that helps it reach and penetrate and egg Oocyte much larger and complex; as it grows in volume, enzymes, mRNA transcripts, and other factors stockpiled in cytoplasm When an oocyte is fertilized a zygote enters cleavage band of microfilaments just beneath PM at cell midsection contracts until cell splits entirely into two blastomeres, each with a copy of the nucleus but different parts of cytoplasm - Differ e n t bl a s t o m e r e s r e c eiv e diff er e n t m a t e r n al m e s s a g e s - Cyt o pl a s mic loc aliz a tio n o u t c o m e of cl e a v a g e ; h el p s s e al t h e d e v elo p m e n t al fa t e of e a c h lin e a g e Ob s e r v a bl e diff er e n c e s in h o w a ni m al s d e v elo p s t a r t s h o win g u p d u rin g cl e a v a g e - Early c u t s follow s p e ci e s s p e cific p a t t e r n s - Ra di al cl e a v a g e (si m pl e s t) c u t s p e r p e n dic ul ar t o mi t o tic s pi n dl e - In s o m e e g g s c u t s g o all t h e w a y t hr o u g h - Bla s t o c y s t m o r e c u t s pr o d u c e a h ollow b all of c ells, o u t e r c ells s e cr e t e fluid t o fill in n e r c a v o t h e r c ells clu s t e r a g ai n s t o n e p a r t of t h e c a vity w all o Occ a sio n ally, firs t t w o bl a s t o m e r e s , t h e in n e r c ell m a s s , or e v e n t h e bl a s t o c y s t s plit s in t cr e a ti n g id e n tic al t win s o Two o o c yt e s r el e a s e d d u rin g t h e s a m e m e n t al c y cl e a r e fer tiliz e d b y t w o s p e r m 38.4 How Do Specialized Tissues and Organs Form? First cavity to form in protostome gastrulas becomes a mouth Anterior-to-posterior body axis forms in gastrulas In vertebrates, this axis precedes formation of neural tube forerunner of brain and spinal cord All cells of a normal embryo have the same number and kinds of genes, having descended from the same zygote; they all activate genes for products to assure survival (e.g. histones and glucosemetabolizing enzymes) But from gastrulation onward, cell lineages engage in selective gene expression (begin of cell differentiation) Cell diff er e n ti a tio n c ell lin e a g e s b e c o m e s p e ci aliz e d in t h eir c o m p o sitio n, s tr u c t ur e, a n d fu nc tio n Mor p h o g e n e si s s p e ci aliz e d tis s u e s a n d or g a n s for m in a pr o gr a m m e d , or d e rly s e q u e n c e Cells of diff er e n t lin e a g e s divid e , gr o w, mi gr a t e , a n d c h a n g e in siz e Tis s u e s le n g t h e n or wid e n a n d fold o v e r a s t h eir c ells c h a n g e in s h a p e So m e c ells di e in c o n tr olle d w a y s a t s p e cific loc a tio n s t o s c ul p t b o d y p a r t s Migr a tio n s c o or di n a t e d b y t h e s y n t h e si s, r el e a s e , d e p o sitio n, a n d r e m o v al of s p e cific c h e mi t h e e x tr a c ellul ar m a t rix 5. Pattern Formation Embryonic induction changes in the developmental fate of embryonic cell lineages exposed to gene products from cells of different tissues - An e m b r y o nic c ell lock e d in a tis s u e s el e c tiv ely r e a d s its g e n e s ; m a y m a k e a n d s e cr e t e si g n m ol e c ul e s t h a t aff e c t its n ei g h b o r s - Sig n al s diffu sin g t hr o u g h its n ei g h b or h o o d m a y in d u c e c h a n g e s in its c o m p o sitio n/ s tr u c t ur e - D e s c e n d a n t s inh e rit a c h e mic al m e m o r y of t h e c h a n g e s a n d g o o n t o for m tis s u e s a n d or g a e x p e c t e d pl a c e s - Pat t er n for m a tio n t hr o u g h c h a n g e s , s p e ci aliz e d tis s u e s a n d or g a n s e m e r g e fro m clu m p s o e m b r y o nic c ells in pr e dic t a bl e pl a c e s , in t h e pr o p e r or d e r S h or t-r a n g e si g n al s c a n c a u s e a c ell t o s tick t o its n ei g h b or s, or b r e a k fr e e a n d mi g r a t e t o a diff er e n t loc a tio n, or b e c o m e s e gr e g a t e d fro m t h e c ells of a n a djoinin g tis s u e Lon g-r a n g e si g n al s a c t o n c o n tr ol el e m e n t s in DNA of e m b r y o nic c ells t h a t a r e far a w a y - m o r p h o g e n s lon g-r a n g e si g n al s; d e g r a d a bl e m ol e c ul e s t h a t diffu s e o u t of a si g n alin g c e n t wit h c o n c e n t r a tio n w e a k e ni n g wit h di s t a n c e o cr e a t e a gr a di e n t t h a t h el p s a c ell c h e mi c ally a s s e s s its p o sitio n in t h e e m b r y o a n d t h u s influ e n c e h o w it will diff er e n ti a t e o s u c h diff er e n c e s in a sig n alin g m ol e c ul e's c o n c e n t r a tio n in d u c e lin e a g e s of c ells p o sitio n diff er e n t loc a tio n s al o n g t h e g r a di e n t t o r e a d diff er e n t p a r t s of t h e s a m e g e n o m e Th e ory of p a t t e r n for m a tio n s a m e kin d s of g e n e s a r e m a p m a k e r s for all m aj or gr o u p s of a ni m al s; pr o d u c t s of g e n e s int e r a c t in w a y s t h a t m a p o u t b a sic b o d y pl a n 1. For m a tio n of tis s u e s a n d or g a n s in or d er e d s p e ci al p a t t e r n s s t a r t s wit h cy t o pl a s mic loc aliz a Co ntin u e s t hr o u g h s h or t-r a n g e , c ell-t o-c ell c o n t a c t s a n d c o n tin u e s t hr o u g h lon g-r a n g e si g n a (c h e mic al g r a di e n t s) e x p o si n g c ells t o diff er e n t c h e mic al infor m a tio n 2. Mor p h o g e n s a n d o t h e r ind u c e r m ol e c ul e s diffu s e t hr o u g h e m b r y o nic tis s u e s , a c tiv a ti n g cl a s m a s t e r g e n e s in s e q u e n c e ; pr o d u c t s of t h e s e g e n e s int e r a c t wit h c o n tr ol el e m e n t s t o lay fou n d a tio n of b a sic b o d y pl a n 3. Pro d u c t s of h o m e o tic g e n e s a n d o t h e r m a s t e r g e n e s int e r a c t wit h c o n tr ol el e m e n t s t o m a p b o d y pl a n; for m w h e n block s of g e n e s a r e a c tiv a t e d/ s u p pr e s s e d in c ells alo n g a n t e rior-p o s t e a xi s a n d d or s al-v e n t r al a xi s of t h e e m b r y o; o t h e r g e n e pr o d u c t s int e r a c t t o fill in d e t ails of s p e cific b o d y p a r t s - On c e a pl a n is lock e d in, ind u c tio n s t h a t follow h a v e o nly loc aliz e d eff e c t s - Body plans cannot change much because of physical (surface-to-volume ratio), architectura (body axes), and phyletic (imposed on each lineage by interactions of master organizer gen which operate when organs form and control induction of the basic body plan) constraints 6. Reproductive System of Human Males testes male gonads; start to form on wall of an XY embryo's abdominal cavity before birth they descend into the scrotum skin pouch below pelvic girdle muscle contractions draw the pouch closer to the main body mass; muscle relaxation lower helps maintain internal temperature packed within each testis are many small, highly coiled tubes called seminiferous tubules sperm production and the emergence of secondary sexual traits start at puberty enlarged testes, growth spurts, deepening voice, more hair growth mammalian sperm travel from the testes through a series of ducts that lead to the urethra not quite mature when sperm enter the epididymes pair of long, coiled ducts last part of epididymis stores mature sperm unused sperm resorbed or excreted in urine in a sexually aroused male, muscles in the wall of the reproductive organs contract, which p mature sperm into and through a pair of thick-walled tubes called vasa deferentia more contractions propel the sperm farther, through a pair of ejaculatory ducts, then throug urethra this last tubular duct runs through the penis and opens at its tip sperm traveling through the urethra mix with glandular secretions and form semen, a thicke fluid that is expelled from the penis during sexual activity - - 7. Sperm Formation Each testis is smaller than a golfball and contains hundreds of wedgeshaped partitions Each lobe contains 1 to 3 coiled tubules Inside each tubeule wall are spermatogonia undifferentiated, diploid cells that divide continuously Descendent cells force older ones toward the interior During departure, daughter cells enter meiosis (primary spermatocytes) Cytoplasmic divisions that accompany nuclear divisions are incomplete and thin cytoplasmi bridges connect the cells o Ions and molecules concerned with development diffuse freely across bridges that conne the cells of each generation and cause them to mature simultaneously All the while, primary spermatocytes receive nourishment and signals from Sertoli cells Secondary spermatocytes form after each primary finishes meiosis I; haploid cells with chromosomes in the duplicated state Sister chromatids of each chromosome move away from each other during meiosis II Haploid daughter cells form (spermatids) Cell begins to mature into a sperm Mature sperm is flagellated: head packed with DNA; tail has microtubular core Essential for sperm formation: testosterone steroid hormone; governs growth, structure, and function of male reproductiv tract; triggers development of secondary sex traits; stimulates sexual and aggressive behav o secreted by leydig cells in testes anterior lobe of pituitary gland makes and secretes LH and FSH hypothalamus governs secretion of GnRH when blood levels of testosterone and other facto low 8. Reproductive System of Human Females Ovaries produce oocytes and secrete sex hormones released oocyte enters oviduct (Fallopian tubes) which opens to uterus myometrium thick layer of smooth muscle; makes up most of uterine wall endometrium uterine lining; consists of connective tissues, blood vessels, and glands cervix narrowed-down part of uterus, connects with a muscular tube, the vagina m u c u s-s e cr e tin g e pi t h eliu m lin e s v a gi n a , w hic h e x t e n d s fro m c e r vix t o b o d y's s u rf a c e la bi a m aj or a o u t e r m o s t p air of s kin fold s p a d d e d wit h a di p o s e tis s u e la bi a mi n or a p air of s m all er fold s h a vi n g m a n y blo o d v e s s el s; e n clo s e d b y la bi a m aj or a clitoris e n clo s e d b y folds; d e riv e d fro m s a m e e m b r y o nic tis s u e a s m al e p e ni s ur e t hr a o p e n s a t b o d y s u rf a c e a b o u t mi d w a y b e t w e e n v a gi n al o p e ni n g a n d clitoris fe m al e s of m o s t m a m m ali a n s p e ci e s follow e s tr o u s cy cl e in " h e a t " or fer til e h u m a n s follow m e n s t r u al c y cl e fertil e o n c y clic b a si s; n o t s y n c hr o niz e d wit h s e x u al r e c e p t e s t or g e n s a n d pr o g e s t e r o n e g ui d e cy clic g r o w t h/r el e a s e of o o c y t e s fro m o v a r y a n d r e b uildin e n d o m e t riu m , w hic h d e p e n d s o n w h e t h e r p r e g n a n c y o c c ur s 9. Preparations for Pregnancy Primary oocyte immature egg arrested in prophase I of meiosis Only o n e s in ov a ri e s for m e d w hil e s h e h e r s elf w a s a n e m b r y o Follicle c o n sis t s of a p ri m a r y o o c y t e a n d a lay e r of c ells t h a t s u rro u n d a n d n o u ris h it; a n o v a h ol d s m a n y follicl e s Hypo t h al a m u s s e cr e t e s e n o u g h GnRH t o m a k e c ells in a n t e rior lob e of t h e pit uit a ry s t e p u p a n d LH s e cr e tio n s h or m o n e s trig g e r gr o w t h of t h e o o c y t e a n d for m a tio n of m o r e c ells a r o u it glyc o pr ot ei n m ol e c ul e s a c c u m ul a t e u n d e r s urr o u n di n g c ells a n d for m zo n a p ellucid a (n o n c ellul ar lay e r) 8 t o 1 0 h o ur s b ef or e r el e a s e o o c y t e c o m pl e t e s m ei o sis I Cyt o pl a s m divid e s u n e v e nly; s e c o n d a r y o o c y t e r e c eiv e s m o s t c y t o pl a s m ; o t h e r is firs t of t hr p ol ar b o di e s t h a t for m b y w a y of m ei o sis a n d d e g e n e r a t e FSH a n d LH c oll e c t in fluid in follicle a n d pr o d c ells t o s e cr e t e e s tr o g e n s Abou t h alfw a y t hr o u g h c ycl e, pit uit a ry r e s p o n d s t o incr e a s e s s e cr e t e s LH in b ri ef p ul s e follicl e s w ells a n d w all w e a k e n s a n d r u p t ur e s fluid a n d s e c o n d a r y o o c y t e r el e a s e d Midcycl e s ur g e of LH trig g e r s o v ul a tio n r el e a s e of s e c o n d a r y o o c y t e fro m o v a r y Estro g e n s r el e a s e d e a rli er al s o c all for gr o w t h of e n d o m e t riu m a n d its gl a n d s , s e t ti n g s t a g e pr e g n a n c y Befor e mi d c ycl e LH s ur g e , follicle c ells w er e b u s y s e cr e ti n g pr o g e s t e r o n e a n d e s tr o g e n s Bloo d v e s s el s gr e w fa s t in t hick e n e d e n d o m e t ri u m At ov ul a tio n, e s tr o g e n s pr o m p t e d c ells of c e r vic al c a n al t o r el e a s e a t hi n, cl e a r m u c u s m e d for s p e r m t o s wi m t hr o u g h Midcycl e s ur g e of LH al s o s ti m ul a t e s c ells in r u p t ur e d follicle t o for m c or p u s lut e u m br e a k s d o w n w h e n w o m a n d o e s n't g e t pr e g n a n t Fe e d b a c k loo p s t o t h e h y p o t h al a m u s a n d pit uit a ry fro m o v a ri e s a n d lat e r, t h e c or p u s lut e u m c o n tr ol t h e c yclic c h a n g e s in t h e o v a ry a n d u t e rin e linin g 10. Pregnancy Happens Penis of unaroused males stays limp because large blood vessels that supply the spongy tissue remain vasoconstricted; male becomes aroused vessels vasodilate Fertilization occurs if they arrive a few days before or after or anytime during ovulation - Less than thirty minutes after sperm arrives in vagina, contractions move them deep into female's reproductive tract A few h u n dr e d a c t u ally r e a c h t h e u p p e r p a r t of t h e o vid u c t, w h e r e e g g s a r e u s u ally fertiliz e m a n y s p e r m bi n d t o o o c yt e's zo n a p ellu cid a bi n di n g trig g e r s r el e a s e of e n z y m e s fro m c a p o v e r e a c h s p e r m' s h e a d c oll e c tiv ely t h e s e di g e s tiv e e n z y m e s m a k e a p a s s a g e t hr o u g h t h e zo n a p ellucid a o nly o n e s p e r m e n t e r s s e c o n d a r y o o c y t e o nly its n u cl e u s a n d c e n t riol e s d o n o t d e g e n e r a t e u n d e r s p e r m p e n e t r a tio n, t h e s e c o n d a r y o o c y t e a n d first p ol ar b o d y c o m pl e t e m ei o sis II n o w t h e r e a r e t hr e e p ol ar b o di e s a n d o n e m a t u r e e g g , t h e o v u m t h e e g g n u cl e u s fus e s wit h s p e r m n u cl e u s , r e s t o rin g di ploid n u m b e r for n e w zy g o t e 38.14 Formation of the Early Embryo all major organs form during the embryonic period third to the end of the eighth week after this period, new individual is called a fetus - h a s di s tinc tly h u m a n fe a t ur e s in fe t al p e rio d, fro m s t a r t of ni n t h w e e k int o birt h, or g a n s gr o w a n d b e c o m e s p e ci aliz e d 3-4 d a y s aft e r fer tiliz a tio n, cl e a v a g e h a s b e g u n o n zy g o t e - G e n e s a r e b ei n g e x pr e s s e d ; e a rly c u t s r e q uir e pr o d u c t s At ei g h t-c ell s t a g e , c ells h u d dl e int o b all Bla s t o c y s t for m s b y fift h d a y - Co n sis t s of tr o p h o bl a s t s u rf a c e lay e r of c ells, bl a s t o c o el fille d wit h t h eir s e cr e tio n s, a n d in c ell m a s s 1-2 d a y s lat e r, im pl a n t a tio n bl a s t o c y s t a d h e r e s t o u t e rin e linin g a n d inv a d e s m o t h e r's tis s for mi n g c o n n e c tio n s t h a t will m e t a b olic ally s u p p o r t p r e g n a n c y - By t his ti m e , inn e r c ell m a s s h a s b e c o m e t w o fla t t e n e d lay e r s of c ells in s h a p e of disk - E m br yo nic di sk will giv e ris e t o t h e e m b r y o pr o p e r As im pl a n t a tio n c o n ti n u e s , m e m b r a n e s for m o u t sid e of e m b r y o 1. Fluid-fille d a m ni otic c a vity o p e n s u p b e t w e e n e m b r y o nic disk a n d p a r t of bl a s t o c y s t s u rf a c e 2. Ma ny c ells mi gr a t e a r o u n d w all of c a vity a n d for m a m nio n m e m b r a n e t h a t will e n clo s e it 3. Fluid fu nc tio n s a s b u o y a n t cr a dl e in w hic h e m b r y o c a n g r o w, m o v e fr e ely, a n d b e pr o t e c t e d a b r u p t t e m p e r a t ur e c h a n g e s a n d m e c h a nic al im p a c t s 4. As a m ni o n for m s , o t h e r c ells mi g r a t e a r o u n d in n e r w all of bl a s t o c y s t, for mi n g linin g t h a t b e c o m e s a yolk s a c a . On e p a r t of yolk s a c b e c o m e s sit e of blo o d c ell for m a tio n b. Anot h e r p a r t giv e s ris e t o g e r m c ells, t h e for e r u n n e r s of g a m e t e s 5. Befor e a bl a s t o c y s t is fully im pl a n t e d , s p a c e s o p e n in m a t e r n al tis s u e s a n d b e c o m e fille d wi bloo d t h a t s e e p s in fro m r u p t ur e d c a pillari e s; in bl a s t o c y s t, a n e w c a vity o p e n s a r o u n d a m n a n d yolk s a c 6. Fing e rlike pr oj e c tio n s for m o n linin g of c a vity, b e c o mi n g t h e t hir d m e m b r a n e , a c h orio n wi b e c o m e p a r t of pl a c e n t a s p o n g y, blo o d e n g or g e d tis s u e 7. Aft er bl a s t o c y s t is im pl a n t e d , a n o u t p o u c hi n g y olk s a c will b e c o m e fo ur t h e x tr a e m b r y o nic m e m b r a n e t h e all a n t ois diff er e n t rol e s in diff er e n t gr o u p s Bla s t o c y s t s t o p s m e n s t r u a tio n - Cells of bl a s t o c y s t s e cr e t e HCG s ti m ul a t e s c or p u s lut e u m t o c o n tin u e s e cr e ti n g pr o g e s t e r o a n d e s tr o g e n s u n til pl a c e n t a t ak e s o v e r 1 1 w e e k s la t e r By s t a r t of t hird w e e k, HC G is d e t e c t a bl e in s a m plin g s of m o t h e r's blo o d a n d u rin e 38.15 Emergence of the Vertebrate Body Plan - Primitive streak depression appears on embryonic disk (surrounded by amnion and chorion except where stalk joins it to chorion wall) and its sides thicken Len g t h e n s a n d t hick e n s t h e n e x t d a y Towar d t h e e n d of t h e t hird w e e k, m ul tipl e p air e d s e g m e n t s c all e d s o mit e s for m fro m p a r t o m e soder m s o mit e s e m b r y o nic s o ur c e s of m o s t b o n e s , sk el e t al m u s cl e s of h e a d a n d tr u n k, a n d of d e r p h a r y n g e al a r c h e s s t a r t t o for m t h a t will c o n trib u t e t o fac e , n e c k, m o u t h , n o s e , lary n x, a n d p h arynx tiny s p a c e s o p e n in p a r t s of m e s o d e r m in ti m e , s p a c e s will int er c o n n e c t a s a c o elo mic c a vity 38.16 Why is the Placenta So Important? By the third week, tiny fingerlike projections from chorion have grown into the maternal blood that has pooled in endometrial spaces. Projections called chorionic villi enhance rate of exchange of substances between mother and embryo placenta blood-engorged organ composed of the uterine lining and extraembryonic membranes - a t full t e r m it will m a k e u p a b o u t in n e r s u rf a c e of u t e r u s - b o d y's w a y of s u s t ai nin g n e w in divid u al w hil e allow its blo o d v e s s el s t o d e v elo p s e p a r a t ely t h e m o t h e r's oxy g e n a n d vit al n u t ri e n t s diffu s e o u t of m a t e r n al blo o d v e s s el s, a c r o s s pl a c e n t a' s blo o d-fill s p a c e s , t h e n int o e m b r y o nic blo o d v e s s el s - v e s s el s c o n v e r g e in a n u m bilic al c or d lifelin e b e t w e e n pl a c e n t a a n d n e w in divid u al - c a r b o n dioxid e a n d o t h e r w a s t e s diffu s e in t h e o t h e r dir e c tio n o m o t h e r's lun g s a n d kid n e y s di s p o s e of t h e w a s t e s af t e r t hird m o n t h, pl a c e n t a s e cr e t e s pr o g e s t e r o n e a n d e s tr o g e n s t o m ai n t ai n u t e rin e linin g 38.17 Emergence of Distinctly Human Features end of fourth week: embryo is 500 times its starting size weeks five and sex: boundary between embryonic and fetal periods growth slows as details of organs fill in - lim b s for m , t o e s a n d fing e r s a r e s c ul p t e d fro m p a d dl e s , u m bilic al c or d for m s, intric a t e circ ul s y s t e m for m s - gr owt h of h e a d s u r p a s s e s t h a t of all o t h e r r e gio n s - r e pr o d u c tiv e or g a n s s t a r t for mi n g e n d of ei g h t h w e e k: individ u al is h u m a n fe t u s s e c o n d tri m e s t e r: n e r v e s a n d m u s cl e s d e v elo p a n d c o n n e c t, r eflexiv e m o v e m e n t s b e gi n - le g s kick, a r m s w a v e , fing e r s g r a s p - fe t u s frow n s, s q ui nt s, p u ck e r s lip s, s u ck s, a n d hic c u p s fiv e m o n t h s old: h e a r t b e a t c a n b e h e a r d t hr o u g h s t e t h o s c o p e b y n o w s kin of fe t u s c ov er e d wit h s oft, fuzzy h air, t h e la n u g o - a t hick c h e e s elik e c o a tin g pr o t e c t s t h e wrinkl e d, r e d dis h s kin fro m a b r a sio n sixt h m o n t h: d elic a t e e y elid s a n d e y el a s h e s for m s e v e n t h m o n t h: e y e s o p e n; all p o r tio n s of b r ai n h a v e for m e d a n d b e g a n fu n c tio nin g 38.18 Mother as Provider, Protector, Potential Threat pregnant woman must gain 20 to 25 pounds IgG antibodies in pregnant woman's blood cross placenta - Prot e c t c hild fro m all b u t m o s t s e rio u s b a c t e ri al inf e c tio n s 38.19 From Birth Onward labor birth process - a m nio n r u p t ur e s jus t b ef or e birt h, s o a m ni o tic fluid d r ai n s fro m v a gi n a - c e r vic al c a n al dil a t e s - fe t u s m o v e s o u t of u t e r u s - t h e n o u t of v a gi n a m ild u t e rin e c o n t r a c tio n s s t a r t in la s t tri m e s t e r r el a xin h or m o n e s e cr e t e d b y o v a ri e s a n d pl a c e n t a - s oft e n s c e r vic al c o n n e c tiv e tis s u e s a n d loo s e n s lig a m e n t s b e t w e e n p elvic b o n e s - fe t u s s hift s d o w n; h e a d u s u ally t o u c h e s c e r vix - r hyt h mic c o n t r a c tio n s a t t h e o n s e t of la b or g e t s tr o n g e r a n d clo s e r t o g e t h e r d u rin g n e x t t w o ei g h t e e n h o ur s, n or m ally c a u si n g e x p ul sio n of fe t u s wit hin a n h o u r af t e r t h e c e r vix is fully d s tr o n g c o n t r a c tio n s d e t a c h pl a c e n t a fro m u t e r u s a n d e x p el it - c o n t r a c tio n s h el p s t o p bl e e di n g b y c o n s t ric tin g blo o d v e s s el s a t r u p t ur e d a t t a c h m e n t sit e u m bilic al c or d c u t a n d ti e d off, t h e n falls off a fe w d a y s la t e r t o for m n a v el CRH aff e c t s ti min g of la b or a n d m a y c o n t rib u t e t o p o s t-p a r t u m d e p r e s sio n - Sti m ul a t e s a d r e n al c or t e x t o s e cr e t e c or tis ol m a y h el p m o t h e r c o p e wit h m a n y s t r ai n s o Durin g pr e g n a n c y, a hi g h lev el of c or tis ol c a n s u p p r e s s CRH p r o d u c tio n b y t h e h y p o t h al a - Aft er birt h, CRH lev el bri efly pl u m m e t s trig g e r s s h o r t-t e r m d e p r e s sio n t h a t t y pic ally c o n ti n u n til t h e h y p o t h al a m u s r e s u m e s its n or m al pr o d u c tio n of CRH lac t a tio n m ilk pr o d u c tio n in m a m m a r y gl a n d s in sid e a m o t h e r's br e a s t s - for a fe w d a y s af t e r birt h, m a m m a r y gl a n d s p r o d u c e a fluid ric h in pr o t ei n s a n d lac t o s e pr ol a c tin h or m o n e t h a t c alls for s y n t h e si s of e n z y m e s u s e d in m ilk p r o d u c tio n, is s e cr e t e d a n t e rior lob e of m o t h e r's pit uit a r y gl a n d oxyt ocin a s n e w b or n s u c k s, pit uit a r y r el e a s e s t hi s h or m o n e - trig g e r s c o n tr a c tio n s t h a t forc e fluid int o milk d u c t s - c a u s e s c o n t r a c tio n s of u t e rin e m u s cl e s t o h el p m a k e u t e r u s s h rink t o its pr e-pr e g n a n c y siz e ...
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This note was uploaded on 05/01/2008 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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