NCM 107 Reproductive System Review PDF

NCM 107 ▪ Prostate gland ▪ Urethra Review of Anatomy & Physiology of Human ▪ Bulbourethral glands Reproductive System Anatomy and Physiology...

NCM 107 ▪ Prostate gland ▪ Urethra Review of Anatomy & Physiology of Human ▪ Bulbourethral glands Reproductive System Anatomy and Physiology of the Reproductive System EPIDIDYMIS GYNECOLOGY - Study of the female reproductive organs ▪ Coiled tube approx. 20 ft. long ANDROLOGY - Study of the male reproductive organs ▪ Found on the superior part of the testis and along the posterior lateral side Male Reproductive System ▪ Functions to store and mature sperm cells 10 – 20 days to travel epididymis ▪ Gonads - Primary sex organs 64 days to reach maturity Testes (males) Ovaries (females) EPIDIDYMIS Body organs that produces sex cells (gametes) ▪ Expels sperm with the contraction of muscles in the Sperm – male gametes epididymis walls to the vas deferens Ova (eggs) – female gametes Secrete hormone DUCTUS (VAS) DEFERENS ▪ Hollow tube surrounded by arteries and veins and External Structures (Male) protected by thick fibrous coating ▪ Carries sperm from the epididymis into the ▪ Testes abdominal cavity seminal vesicles and ejaculatory ▪ Penis ducts (thru peristalsis) TESTES DUCTUS (VAS) DEFERENS ▪ 2 ovoid glands ▪ 2-3cm wide ▪ Sperm mature as they pass thru the vas deferens ▪ scrotum (rugated, skin-covered, muscular pouch) ▪ Spermatic cord – blood vessels and vas deferens Supports testes and help regulate temp. of sperm together ▪ Ends in the ejaculatory duct w/c unites with the urethra PENIS ▪ Tubular organ that surrounds the latter part of the ◼Vasectomy – cutting of vas deferens @ the level of the urethra testes to prevent transport of sperm; male birth control ▪ Purposes: Outlet of urine Delivers sperm into the female reproductive system URETHRA ▪ Extends from the base of the urinary bladder to the Regions of the Penis: tip of the penis ▪ Carries both urine and sperm ▪ Shaft ▪ Approx. 8 inches (18 – 20 cm) ▪ Glans penis (enlarged tip) ▪ Prepuce (foreskin) Folded cuff of skin around proximal end SEMINAL VESICLES Often removed by circumcision ▪ 2 convoluted pouches along the base of the bladder 3 cylindrical masses of erectile tissue in the shaft: SEMINAL VESICLES ▪ 2 corpus cavernosa ▪ Secrete 60% semen that is viscous (thick), yellowish ▪ Corpus spongiosum Basic sugar (fructose) Normally not filled with much blood Protein Sexual excitement Prostaglandins Other substances that nourish and activate sperm Sexual Excitement ▪ Nitric oxide released from blood vessels PROSTATE GLAND ▪ Dilatation of blood vessels and  in blood flow to the arteries of the penis (engorgement) ▪ Chestnut – sized gland ▪ Penis becomes longer, wider and rigid (erection) ▪ Encircles the upper part of the urethra ▪ Secretes a thin, alkaline fluid Male Internal Structures When added to the secretion from seminal vesicles and sperm – protects sperm from being immobilized ▪ Epididymis ▪ Vas deferens (ductus deferens) ▪ Seminal vesicles BULBOURETHRAL GLANDS ▪ Ejaculatory ducts ▪ Cowper’s glands ▪ Lie beside the prostate gland and empty by short ducts into the urethra Fourchette BULBOURETHRAL GLANDS ▪ Ridge of tissue formed by the posterior joining of the labia minora and majora ▪ Secretes thick, clear, alkaline fluid ▪ Structure that is sometimes cut during childbirth to Cleanses urethra of acidic urine enlarge vaginal opening (episiotomy) Ensure safe passage of sperm Serves as lubricant during sexual intercourse Hymen ▪ Tough but elastic semi-circle of tissue that covers SEMEN the opening to the vagina in childhood ▪ Milky mixture of sperm and accessory gland ▪ Often torn during the time of 1st intercourse secretions Use of tampons ▪ Alkaline – pH 7.2 – 7.6 – helps neutralize acidic Active sports environment of the vagina (pH 3.5 – 4) ▪ Contains seminal plasmin – inhibits bacterial Internal Structures multiplication ▪ Relaxin and enzymes – enhance sperm motility ▪ Ovaries ▪ 2 – 5 mL semen propelled out ▪ Fallopian tubes ▪ 50 – 130 million sperm/mL ▪ Uterus ▪ Vagina Female Reproductive System OVARIES ▪ External Genitalia Vulva (Latin – covering) ▪ 4cm long, 2cm diameter, 1.5cm thick (size and Mons veneris, labia minora, labia majora shape of almonds) Vestibule, clitoris, Skene’s glands, fourchette, ▪ Grayish-white and appears pitted (w/ indentations hymen on the surface) ▪ Composed of ovarian follicles (sac-like structures) structures: oocyte (immature ova), follicular cells ▪ Mons pubis Pad of adipose tissue located over the symphysis pubis Ovarian Follicle stages: Covered by pubic hair Protect the junction of pubic bone from trauma ▪ Primary follicle – contains an immature oocyte ▪ Graafian (vesicular) follicle – growing follicle with a maturing oocyte ▪ Labia Minora ▪ Ovulation – when the egg is mature follicle ruptures Hairless folds of connective tissue Occurs about every 28 days Majora ▪ Ruptured follicle is transformed into a corpus Pubic hair luteum Protect external genitalia and distal urethra and vagina Functions of the 2 ovaries: Other external organs ▪ To produce, mature, and to discharge ova (egg cells) ▪ In the process, produces estrogen and progesterone ▪ Vestibule – initiate and regulate menstrual cycles Flattened smooth surface inside the labia Urethra and Vagina both arise here ⚫NO ESTROGEN: breasts prevented from maturing @ puberty Clitoris Menopause – uterus, breast, ovaries will atrophy ▪ 1 – 2 cm, rounded organ of erectile tissue ▪ Covered by a fold of skin (prepuce) ▪ Ovarian fxn necessary for maturation and ▪ Sensitive to touch and temp; center of sexual maintenance of 2ndary sex characteristics arousal and orgasm in female Ovaries ▪ Suspended @ the end of the fallopian tubes by 3 Skene’s glands strong supporting ligaments attached to the uterus or pelvic wall ▪ Paraurethral glands Suspensory ligaments – secure ovaries to lateral Located lateral to the urinary meatus, one on each walls of the pelvis side Ovarian ligaments – attach to uterus ▪ Bartholin’s glands (vulvovaginal) Broad ligament – a fold of the peritoneum, encloses Lateral to vaginal opening on both sides suspensory ligament ▪ Secretions from both help lubricate external genitalia during coitus Alkaline pH improve sperm survival in the vagina FALLOPIAN TUBES ▪ Smooth, hollow tunnel Sloughs off if no pregnancy occurs (menstruation) ▪ Approx. 10 cm in length (Adult) Uterine coats/walls: ▪ Fxn: ▪ Myometrium To convey the ovum from the ovaries to the uterus Middle layer of smooth muscle Provide a place for fertilization of the ovum by the sperm Constricts tubal junctions preventing regurgitation of menstrual blood into the tubes Holds internal cervical os closed during pregnancy to 4 separate portions: prevent preterm birth Portion where myomas and benign uterine tumors ▪ Interstitial portion – lies w/in the uterus; 1 cm long; arise lumen is 1 mm in diameter ▪ Isthmus – 2 cm long; portion that is cut or sealed in tubal ligation; ▪ Perimetrium ▪ Ampulla – longest – 5 cm long; portion where Outermost layer fertilization occurs Adds strength and support to the uterus ▪ Infundibulum – most distal segment; 2 cm long; funnel-shaped; rim is covered by fimbriae (small hairs) Uterine Deviations ▪ Cilia inside the uterine tube slowly move the oocyte ▪ A number of uterine deviations – shape and towards the uterus (takes 3 – 4 days) position – may interfere with fertility or pregnancy Bicornuate uterus – oddly shaped “horns” @ the UTERUS junction of the fallopian tubes Septum Dividing uterus ▪ Hollow, muscular, pear-shaped organ Double uterus ▪ Located between urinary bladder and rectum ⚫May decrease ability to conceive and carry fetus to term ⚫Less placenta implantation space Functions of the Uterus: ▪ Receive the ovum from the fallopian tube Positional Deviations of the Uterus ▪ Provide a place for implantation and nourishment ▪ Normally uterus is tipped slightly forward during fetal growth ▪ Anteversion – fundus tipped forward ▪ Furnish protection to a growing fetus ▪ Retroversion – fundus tipped back ▪ At maturity of the fetus, expel it from a woman’s ▪ Anteflexion – body of uterus bent sharply forward body ▪ Retroflexion – body bent sharply back just above cervix Regions of the Uterus: ▪ Body (corpus) – main portion; expands to contain VAGINA growing fetus ▪ Fundus – can be palpated abdominally to ▪ Hollow, musculomembranous canal determine: ▪ Located behind (posterior) the bladder and in front the amt. of uterine growth occurring during (anterior)of rectum pregnancy ▪ Extends from the cervix of the uterus to the to measure the force of uterine contractions during external vulva labor To assess that the uterus is returning to its Functions of the vagina: nonpregnant state after childbirth ▪ Acts as an organ of intercourse ▪ Conveys sperm to the cervix so sperm can meet w/ ▪ Isthmus – enlarges during pregnancy to the ovum in the fallopian tube accommodate growing fetus; portion commonly ▪ Serves as birth canal cut during C/S PELVIS ▪ Cervix – lowest portion; 1/3 of the total uterus size; narrow outlet that protrudes into the vagina ▪ Serves to support and protect the reproductive and Opening – internal cervical os other pelvic organs Distal opening to the vagina – external os ▪ Bony ring formed by 4 united bones: Level of external os - @ the level of the ischial Innominate bones (flaring hip) spines (impt. rel. in estimating the level of the fetus Coccyx in the birth canal) Sacrum 3 divisions of the innominate bones: Uterine coats/walls: ▪ Ilium – forms the upper and lateral portion ▪ Ischium – inferior portion ▪ Endometrium 2 projections: inner layer Ischial tuberosities – portion on w/c a person sits Important for menstrual function Ischial spines – small projections that extend from the allows for implantation of fertilized egg lateral aspects into the pelvic cavity; midpt. of pelvis 3 divisions of the innominate bones: ▪ Pubis – anterior portion of the innominate bone Symphysis pubis – is the junction of the innominate bones at the front of the pelvis PELVIS ▪ Sacrum – upper portion of the pelvic ring ▪ Coccyx – below the sacrum; composed of 5 very small bones fused together ▪ Stiff, w/ a degree of movement – permits coccyx to be pressed backward, allowing more room for the fetal head to pass during childbirth Obstetric division of Pelvis: ▪ False pelvis – superior half Supports the uterus during late months of pregnancy Aids in directing fetus into the true pelvis for birth ▪ True pelvis – inferior half ▪ Pelvic inlet – entrance to the true pelvis or upper ring of bone thru w/c fetus must pass to be born vaginally; heart-shaped ▪ Pelvic outlet – portion bounded in the back by the coccyx, side by the ischial tuberosities, front by the inferior aspect of the symphysis pubis ▪ Pelvic cavity – space bet. the inlet and the outlet; curved passage The curve slows and controls the speed of birth – reducing sudden pressure changes in the fetal head Compresses chest of fetus – helping expel lung fluid and mucus to prepare lungs for good aeration at birth For a baby to be delivered vaginally – has to pass thru the inlet, cavity, and the outlet FERTILIZATION: THE BEGINNING OF PREGNANCY FERTILIZATION ✓ also referred to as conception, impregnation, or fecundation ✓ the union of an ovum and a spermatozoon ✓ usually occurs in the outer third of a fallopian tube (ampullar portion) OVUM  usually only 1 ovum reaches maturity each month  Immediately after penetration of the ovum, the  Once it is released, fertilization must occur fairly chromosomal material of the ovum and quickly – an ovum is capable of fertilization for only spermatozoon fuse = called a zygote 24 hours (48 hours the most)  Sperm and ovum each carried 23 chromosomes (22  After that time, it atrophies and becomes autosomes and 1 sex chromosome), fertilized ovum nonfunctional has 46 chromosomes  Spermatozoon: functional life 48 hours (possibly as  If an X-carrying sperm entered the ovum = long as 72 hours) resulting child will have 2 X chromosomes  Total critical time span during which sexual and will be FEMALE (XX) intercourse must occur for fertilization to be  If a Y-carrying sperm fertilized the ovum = X successful is about 72 hours ( 48 hours before and a Y chromosome = MALE (XY) ovulation + 24 hours afterward)  Ovum is extruded from the graafian follicle of an ovary w/ ovulation – it is surrounded by a ring of  Fertilization is never a certain occurrence, because it maculopolysaccharide fluid (zona pellucida) and a depends on @ least 3 separate factors: circle of cells (corona radiata)  Equal maturation of both sperm and ovum  The ovum and these surrounding cells (w/c  the  Ability of the sperm to reach the ovum bulk of the ovum and serve as protective buffers  Ability of the sperm to penetrate the zona against injury) are propelled into a nearby fallopian pellucida and cell membrane and achieve fertilization tube by currents initiated by the fimbriae (fine, hair- like structures lining the openings of the fallopian  From the fertilized ovum (zygote), the future child tubes) and also the accessory structures needed for support  Combination of peristaltic action of the tube and during intrauterine life (e.g. placenta, fetal movements of the tube cilia help propel the ovum membranes, amniotic fluid, umbilical cord) all are along the length of the tube formed Terms Used to Denote Fetal Growth SPERMATOZOA  Ejaculation of semen: ave. 2.5 mL of fluid containing 50 – 200 spermatozoa/mL or ave. of 400 million NAME TIME PERIOD sperm/ejaculation Ovum ✓ From ovulation to fertilization  At the time of ovulation – reduction in the viscosity Zygote ✓ From fertilization to implantation (thickness) of the cervical mucus = easier for sperm Embryo ✓ From implantation to 5 – 8 weeks to penetrate it Fetus ✓ From 5 – 8 weeks until term  Sperm transport is so efficient close to ovulation that Conceptus ✓ Developing embryo or fetus and sperm deposited in the vagina during intercourse placental structures throughout generally reach the cervix w/in 80 seconds and the pregnancy outer end of a fallopian tube w/in 5 minutes after deposition = reason why douching is not an effective contraceptive measure  Sperm move by means of their flagella (tails) and uterine contractions thru the cervix and the body of Implantation the uterus and into the fallopian tubes, toward the waiting ovum  The mechanism whereby the sperm are drawn  Once fertilization is complete, the zygote migrates toward an ovum is probably a species-specific over the next 3 – 4 days toward the body of the reaction (similar to an antibody-antigen reaction) uterus – aided by the currents initiated by the  Capacitation – final process that sperm must muscular contractions of the fallopian tubes undergo to be ready for fertilization; happens as the  During this time, mitotic cell division, or cleavage, sperm move toward the ovum; consists of the begins changes in the plasma membrane of the sperm head,  1st cleavage occurs @ about 24 hours w/c reveal the sperm-binding receptor sites  Cleavage divisions continue to occur @ a rate of one  all of the spermatozoa that achieve capacitation about every 22 hours reach the ovum and cluster around the protective  By the time zygote reaches the body of the uterus, it layer of corona cells consists of 16 – 50 cells = because of its bumpy  Hyaluronidase (a proteolytic enzyme) is apparently outward appearance = morula (from the Latin word released by the sperm and acts to dissolve the layer morus, meaning mulberry) of cells protecting the ovum – one reason why  Morulla continues to multiply as it floats free in the ejaculation contains large numbers of sperm is to uterine cavity for 3 or 4 more days provide enough enzymes to dissolve the corona cells  Large cells tend to collect @ the periphery of the ball,  Only one spermatozoon is able to penetrate the cell leaving a fluid space surrounding an inner cell mass membrane of the ovum = structure is now called a blastocyst  Once it penetrates the cell – cell membrane changes  Balstocyst attaches to the uterine endometrium composition to become impervious (resistant or  Cells in the outer ring = trophoblast cells – they are impermeable) to other sperms part of the structure that will later form the placenta  Hydatidiform mole (H-mole) – exception, where and membranes multiple sperm enter; leads to abnormal growth  Inner cell mass (embryoblast cells) – portion of the structure that will form the embryo IMPLANTATION – contact between the growing structure  As the embryo continues to grow, it pushes the and the uterine endometrium decidua capsularis before it like a blanket  Eventually, enlargement brings the structure into  Occurs approximately 8 – 10 days after fertilization contact w/ the opposite uterine wall – the decidua  After the 3rd of 4th day of free floating (about 8 days capsularis fuses w/ the endometrium of the opposite since ovulation), the last residues of the corona and wall zona pellucida are shed by the growing structure  This is why @ birth, the entire inner surface of the  Blastocyst brushes against the rich uterine uterus is stripped away, leaving the organ highly endometrium (in the 2nd [secretory] phase of the susceptible to hemorrhage and infection menstrual cycle), a process termed apposition  It attaches to the surface of the endometrium CHORIONIC VILLI (adhesion) and settles down into its soft folds (invasion)  Blastocyst is able to invade the endometrium because – as trophoblast cells on the outside of the After implantation trophoblast cell matures structure touch the endometrium, they produce  proteolytic enzymes that dissolve the tissue they touch 11th or 12th day – miniature villi (probing “fingers”)  This allows the blastocyst to burrow deeply into the  endometrium and receive some basic nourishment of glycogen and mucoprotein from the endometrial Chorionic villi – reach out from the single layer of cells glands into the uterine endometrium  As invasion continues – structure establishes and  effective communication network w/ the blood system of the endometrium At term almost 200 villi have formed  The touching or implantation point: usually high in the uterus, on the posterior surface  If point of implantation is low in the uterus  Chorionic villi have a central core of loose connective = the growing placenta may occlude the tissue surrounded by a double layer of trophoblast cervix and make birth of the child difficult cells (placenta previa) ▪ Central core of connective tissue – contains  Implantation – important step in pregnancy – as fetal capillaries many as 50% of zygotes never achieve it ▪ Outer of the 2 covering layers is termed the  Pregnancy ends as early as 8 – 10 days after syncytiotrophoblast, or the syncytial layer – conception, often before a woman is even instrumental in the production various aware it had begun placental hormones:  Occasionally, a small amount of vaginal spotting 1. hCG (Human chorionic gonadotrophin) appears w/ implantation – capillaries are ruptured by 2. Somatomammotropin (human placental the implanting trophoblast cells lactogen [hPL])  A woman may mistake implantation bleeding for her 3. Estrogen menstrual period – prediction of the date of birth of 4. Progesterone her baby (based on LMP) will be calculated 4 weeks ▪ Inner layer – cytotrophoblast or Langhan’s late layer – present as early as 12 days’ gestation Appears to function early in pregnancy to protect the growing Embryonic and Fetal Structures embryo and fetus from certain infectious organisms such as the spirochete of syphilis THE DECIDUA Disappears bet. 20th and 24th week =  After fertilization, the corpus luteum in the ovary syphilis have a high potential for continues to function rather than atrophying = fetal damage late in pregnancy influence of human chorionic gonadotrophin (hCG), Offer little protection viral invasion a hormone secreted by the trophoblast cells @ any point  The uterine endometrium, instead of sloughing off as in a normal menstrual cycle, continues to grow in thickness and vascularity = endometrium now termed the decidua (Latin word for falling off) – The Placenta because it will be discarded after birth of the child  Decidua has 3 separate areas:  Latin for pancake – w/c is descriptive of its size and 1. Decidua basalis – part of the endometrium that appearance @ term lies directly under the embryo (or the portion  Arises out of trophoblast tissue (fetal in origin) where the trophoblast cells are establishing  Serves as fetal lungs, kidneys, and GI tract, and as a communication w/ maternal blood vessels) separate endocrine organ throughout pregnancy 2. Decidua capsularis – the portion of the  Its growth parallels that of the fetus – from a few endometrium that stretches or encapsulates the identifiable cells @ the beginning of pregnancy to an surface of the trophoblast organ 15 – 20 cm in diameter and 2 – 3 cm in depth 3. Decidua vera – the remaining portion of the @ term uterine lining  Covers about half the surface area of the internal uterus Placental Circulation ▪ A carrier moves the substance into and thru the membrane  12th day of pregnancy – maternal blood begins to ▪ Glucose is an example of a collect in the intervillous surfaces of the uterine substance that crosses by this endometrium surrounding the chorionic villi process  3rd week - oxygen ACTIVE ▪ This process requires energy - glucose TRANSPORT and action of an enzyme to - amino acids facilitate transport ▪ Essential amino acids and - fatty acids diffuse from the water-soluble vitamins cross maternal blood thru the cell layers the placenta against the - minerals of the chorionic pressure gradient or from an villi to the villi capillaries area of lower molecular concentration to an area of - vitamins greater molecular  concentration. ▪ Amino acid concentration in the - water  fetal plasma are twice what they are in the mother then nutrients PINOCYTOSIS ▪ Absorption by the cellular are transported back to membrane of microdroplets of the developing embryo plasma and dissolved substances. ▪ Gamma globulin, lipoproteins,  For practical purposes, there is no direct exchange of phospholipids, and other blood between the embryo and the mother during molecular structures that are pregnancy – exchange is carried out by selective too large for diffusion and that osmosis thru the chorionic villi cannot participate in active  Because chorionic villi layer is only one cell thick – transport cross in this manner minute breaks do allow occasional fetal cells to cross, ▪ Viruses that can infect the fetus as well as enzymes such as alpha – fetoprotein from can also cross in this manner. the fetal liver  Only a few substances are able to cross from the ☺ As the # of chorionic villi increases w/ pregnancy ☺ mother into the fetus ▪ Almost all drugs are able to cross into fetal  circulation – woman should take no nonessential drugs (including alcohol and Villi form an increasingly complex communication nicotine) during pregnancy network w/ the maternal blood  All of the specific mechanisms or processes that  allow nutrients to cross the placenta are affected by: ▪ Maternal blood pressure and Intervillous spaces grow larger and larger ▪ pH of the fetal and maternal plasma  Becoming separated by a series of partitions or septa  MECHANISMS BY WHICH NUTRIENTS CROSS THE PLACENTA (Table 8.2)  MECHANISM DESCRIPTION 30 separate segments (in a matured placenta) = DIFFUSION ▪ When there is a greater cotyledons concentration of a substance on one side of a semipermeable  membrane than on the other, These compartments make maternal side of the substances of correct molecular placenta @ term look rough and uneven weight cross the membrane from the area of higher concentration to the area of lower concentration. ▪ Oxygen, carbon dioxide,  100 maternal uterine arteries supply the mature sodium, and chloride cross the placenta placenta by this method  Rate of uteroplacental blood flow in pregnancy FACILITATED ▪ To ensure that the fetus increases → from 50 mL/min at 10 weeks to 500 – DIFFUSION receives enough concentrations 600 mL/min @ term of necessary growth  No additional maternal arteries appear after the 1 st substances, some substances 3 mos. of pregnancy → to accommodate ed blood cross the placenta more rapidly flow, arteries  in size → mother’s heart rate, total and more easily w/o the cardiac output, and blood volume  to supply the expenditure of energy than placenta would occur if only simple diffusion were operating  Placental Circulation In the intervillous spaces – maternal blood jets from the (shortly after implantation has occurred) coiled through about 100th day of pregnancy ▪ Negative hCG in mother’s serum – w/in 1 – 2 or spiral arteries in streams or spurts weeks after birth  ▪ Testing for hCG can be used as proof that all of the placental tissue has been delivered Maternal blood is then propelled from ▪ Purpose: to act as a fall-safe measure to compartment to compartment ensure that the corpus luteum of the ovary continues to produce progesterone and  estrogen As blood circulates around the villi and If the corpus luteum shd fail → progesterone level falls → nutrients osmose from maternal blood into the villi endometrial sloughing → loss of pregnancy → rise of pituitary  gonadotrophins → inducing a new Maternal blood gradually loses its momentum and menstrual cycle ▪ May also play a role in suppressing the settles to the floor of the cotyledons maternal immunologic response so that  placental tissue is not rejected ▪ 8th week of pregnancy: outer layer of cells of Blood enters the orifices of maternal veins located in the developing placenta begins to produce the cotyledons progesterone – production of hCG begins to  decrease Blood is returned to maternal circulation 2. Estrogen ▪ Primarily estriol; “hormone of women” ▪ Produced as a 2nd product of the syncytial  Braxton Hicks contractions – barely noticeable and cells of the placenta painless uterine contractions; present from about ▪ Contributes to the mother’s mammary gland 12th weeks of pregnancy; aid in maintaining pressure development in preparation for lactation in the intervillous spaces by closing off uterine veins ▪ Stimulates uterine growth to accommodate momentarily w/ each contraction the developing fetus  When mother lies on her LEFT SIDE – most efficient 3. Progesterone uterine perfusion, and placental circulation; this ▪ “hormone of mothers” – progesterone is position lifts the uterus away from the inferior vena necessary in pregnancy to maintain the cava – preventing blood from being trapped in her endometrial lining of the uterus lower extremities ▪ Present in serum – as early as 4th week of ▪ When mother lies on her BACK – weight of pregnancy – as a result of the continuation the uterus compresses the vena cava; of the corpus luteum placental circulation can be sharply reduced ▪ Reduce contractility of the uterine = SUPINE HYPOTENSION (very low maternal musculature during pregnancy = preventing blood pressure) premature labor; probably produced by a  At term – placenta weighs 400 – 600 gms (1lb.) or 1/6 change in electrolytes (potassium and the weight of the baby calcium), w/c decreases contraction ▪ Smaller placenta = inadequate circulation to potential of the uterus the fetus ▪ Bigger placenta = circulation to the fetus was threatened because placenta was forced to 4. Human Placental Lactogen (Human Chorionic spread out in an unusual manner to maintain Somatomammotropin) sufficient blood supply ▪ hPL is a hormone w/ both growth-promoting and lactogenic (milk-producing) properties ▪ produced by the placenta beginning the 6th  Diabetic woman – fetus may develop a larger than week of pregnancy – increasing to a peak usual placenta, probably from excess fluid collected level @ term between cells ▪ can be assayed/assessed in both maternal serum and urine Endocrine Function ▪ promotes mammary gland growth in preparation for lactation in the mother  Syncytial (outer) layer of chorionic villi – serves as ▪ serves the important role of regulating source of oxygen and nutrients, and develops into a maternal glucose, protein, and fat levels so separate, important HORMONE – PRODUCING that adequate amounts of these nutrients system: are always available to the fetus 1. Human Chorionic Gonadotrophin (hCG) ▪ 1st hormone produced ▪ Can be found in maternal blood and urine as The Umbilical Cord early as the 1st missed menstrual period  formed from the fetal membranes (amnion and 2nd membrane lining the chorionic membrane/inner chorion) layer = the amniotic membrane/ amnion  provides a circulatory pathway that connects the embryo to the chorionic villi of the placenta - forms beneath the chorion   Functions: ▪ to transport oxygen and nutrients to the offers support to the amniotic fluid and also produces fetus from the placenta and the fluid; produces phospholipid that initiates the ▪ to return waste products from the fetus to formation of prostaglandins, w/c can cause uterine the placenta contractions  53 cm (21 inches) in length (@ term)  2 cm (3/4 inch) thick and may be the trigger that initiates labor  Wharton’s jelly – bulk of the cord; gelatinous mucopolysaccharide; gives the cord body and prevents pressure on the vein and arteries that pass  the amniotic membranes, like the umbilical cord, thru it they have no nerve supply = neither mother nor child  outer surface – covered w/ amniotic membrane experiences pain when these membranes  the remnant of the yolk sac may be found in the fetal spontaneously rupture @ term or artificially end of the cord – as a white fibrous streak @ term ruptured  Contains: ▪ 1 vein – carrying blood from the placental The Amniotic Fluid villi to the fetus ▪ 2 arteries – carrying blood from the fetus back to the placental villi  # of veins and arteries in the cord is always assessed  constantly being newly formed by the amniotic and recorded @ birth: membrane – never becomes stagnant ▪ 1% of all infants are born w/ a cord that  is reabsorbed @ the rate of 500 mL/24 hours contains a single vein and artery  some of it is probably absorbed by direct contact w/ ▪ 15% of these infants are found to have the fetal surface of the placenta congenital anomalies – particularly of the  major method of absorption happens because fetus kidney and heart continually swallows the fluid  Percutaneous umbilical blood sampling (PUBS) – blood is withdrawn from the umbilical vein or  Method of absorption: transfused into the vein during intrauterine life for fetal assessment or treatment  Rate of blood flow thru an umbilical cord is rapid – Fetus swallows amniotic fluid 350 mL/min @ term  ▪ Impossible that a cord will twist or knot enough to interfere w/ fetal oxygen supply From the fetal intestine, it will be absorbed in the into  Nuchal cord – loose loop of cord around fetal neck; the fetal bloodstream 20% of all births; oxygen supply is not impaired   Walls of the umbilical cord arteries are lined w/ smooth muscle Goes to the umbilical arteries ▪ Constriction of these muscles after birth contributes to hemostasis and helps prevent  hemorrhage of the newborn thru the cord To the placenta  Contains no nerve supply – can be cut @ birth w/o discomfort to either mother or child  And it is exchanged across the placenta The Amniotic Membranes  Amount of amniotic fluid @ term: 800 – 1,200 mL  The chorionic villi on the medial surface of the ▪ If fetus is unable to swallow (esophageal trophoblast (those that are not involved in atresia or anencephaly) = excessive amniotic implantation because thy do not touch the fluid or hydramnios (more than 2,000 mL, or endometrium) – begins to gradually thin, leaving the pockets of fluid lager than 8cm on medial surface smooth ultrasound)  chorion leave, or smooth chorion ▪ Hydramnios also tends to occur in women w/ diabetes – hyperglycemia causes  excessive fluid shift into the amniotic space ▪ Fetal urine (produced early in fetal life, as Eventually becomes the chorionic membrane – soon as fetal kidneys become active) adds to outermost fetal membrane, the quantity of amniotic fluid or the 1st layer of fetal covering ▪ Oligohydramnios – results to a disturbance of fetal kidney function; reduction in the  amount of amniotic fluid (less than 300 mL Once it becomes smooth, it offers support to the sac that in total, or no pocket on ultrasound larger contains the amniotic fluid than 1 cm)  FUNCTIONS of AMNIOTIC FLUID (serves as an  important protective mechanism for the fetus):  1. Shields fetus against pressure or a blow to Primary Germ Layers the mother’s abdomen 2. Protects fetus from changes in temperature – because liquid changes temperature more  Time of implantation ➔ blastocyst is differentiated slowly than air  3. Aids in fetal muscular development – allows fetus the freedom to move 2 separate cavities appear in the inner 4. Protects umbilical cord from pressure, structure protecting the fetal O2 supply    Amniotic fluid is slightly alkaline = pH 7.2 Amniotic cavity Yolk sac  Urine is acidic = pH 5.0 – 5.5  Large one  Smaller cavity  Lined w/ a distinctive  Lined w/ ENTODERM layer of cells - ECTODERM Origin and Development of Organ Systems  Supply nourishment only until implantation  From the moment of fertilization, the zygote and  After, it provides a later the embryo and fetus is composed of active, source of RBC until growing cells. the embryo’s hematopoetic system is mature Stem Cells enough to perform this fxn – about 12th week of intrauterine  1st 4 days of life – zygote cells = totipotent stem life cells, or cells that are so undifferentiated that they  It then atrophies and have the potential to form a complete human being remains only as a thin  white streak After another 4 days, as structure implants and discernible in the becomes an embryo – cells begin to show cord @ birth differentiation and are no longer capable of becoming any body cell  PRIMARY GERM LAYERS:  ▪ ECTODERM – lines the amniotic cavity ▪ ENTODERM – lines the yolk sac Become specific body cells such as nerve, brain, or skin ▪ MESODERM – found bet. Amniotic cavity cells = pluripotent stem cells and yolk sac  Another few days, cells grow so specific = multipotent  Where these 3 layers meet, embryo starts to develop stem cells = EMBRYONIC SHIELD  Each of these germ layers of primary tissue develops - evident what body organ into specific body systems they will create  Knowing w/c structures arise from each germ layer is important – because coexisting congenital defects found in newborns usually arise from the same layer  If nucleus is removed from an oocyte, and adult nucleus is transferred into the oocyte = embryo has the potential to grow into an infant that is identical to the adult donor – reproductive cloning  ORIGIN OF BODY TISSUES (Table 8.3, p. 190)  If it pluripotent stem cells are removed and allowed to grow in the laboratory = has the potential to be GERM LAYER BODY PORTIONS FORMED able to supply any type of body cell needed by the ECTODERM  Central nervous system (brain adult donor – therapeutic cloning and spinal cord)  Peripheral nervous system  Skin, hair, and nails  Sebaceous glands  Sense organs Zygote Growth  Mucous membranes of the anus,  Development proceeds in a cephalocaudal (head-to- mouth and nose tail) direction – head development occurs first,  Tooth enamel followed by the development of the middle and,  Mammary glands finally, the lower body parts MESODERM  Responsible for the formation of  As a fetus grows, body organ systems develop from supporting structures of the body: specific tissue layer called germ layers  Connective tissue  Bones, cartilage   Muscle Blood arriving @ the fetus from the placenta is highly  Ligaments, tendons oxygenated  Dentin of teeth   Upper portion of the urinary system (kidney, ureters) Enters through the umbilical vein  Reproductive system  Heart (called a vein tho’ it carries oxygenated blood – because  Circulatory system direction of the blood is toward the fetal heart)  Blood cells   Lymph vessels ENTODERM  Develops into the lining of: Blood is carried into the inferior vena cava thru an  Pericardial, and peritoneal accessory structure – ductus venosus cavities   Gastrointestinal tract  Respiratory tract, tonsils Allowing oxygenated blood to be supplied directly to  Parathyroid, thyroid, thymus the fetal liver glands   Lower urinary system (bladder and urethra) Oxygenated blood empties into the inferior vena cava   all organ systems are complete, @ least in a Carried to the right side of the heart rudimentary form - @ 8 week’s gestation (end of embryonic period)   Organogenesis – organ formation; growing structure Because there is no need for the bulk of the blood to is most vulnerable to invasion by teratogens (any pass thru the lungs, factor that that affects the fertilized ovum, embryo, or fetus adversely, such as alcohol)  It is shunted as it enters the right atrium, Cardiovascular System  Into the left atrium thru an opening in the atrial  One of the 1st systems to become functional in septum, called the foramen ovale intrauterine life   Simple blood cells joined to the walls of the yolk sac progress to become a network of blood vessels and Follows the course of normal circulation into the left a single heart tube – w/c forms as early as the 16th ventricle and into the aorta day of life; beats as early as the 24th day   Septum that divides the heart into chambers – develops during the 6th or 7th week Transported by the umbilical arteries  Heart valves begin to develop in the 7th week  Heartbeat may be heard w/ a Doppler instrument – (transporting deoxygenated blood – away from the fetal 10th – 12th week of pregnancy heart)  ECG may be recorded on a fetus – as early as 11th back thru the umbilical cord week; more accurate about the 20th week of pregnancy (conduction is more regulated)   Heart rate of fetus is affected by: placental villi – where new oxygen exchange takes place ▪ Fetal oxygen level ▪ Body activity ▪ Circulating blood volume  Fetal blood oxygen saturation level – 80%  Rapid fetal heart rate during pregnancy – 120 – 160 Fetal Circulation beats/min is necessary to supply oxygen to cells, because RBCs are never fully saturated  3rd week of intrauterine life – fetal blood begins to exchange nutrients w/ the maternal circulation across the chorionic villi Fetal Hemoglobin  Fetal circulation differs from extrauterine circulation in several aspects:  Differs from adult hemoglobin in several ways: 1. Fetus derives oxygen and excretes carbon 1. Fetal hemoglobin has a different composition: dioxide not from oxygen exchange in the lungs ▪ Fetus: 2 alpha and 2 gamma chains but from the placenta ▪ Adult: 2 alpha and 2 beta chains 2. It is more concentrated and has greater oxygen 2. Blood does enter the blood vessels of the lungs affinity – 2 features that increase its efficiency while the child is in-utero, but this blood flow is 3. Newborn’s hemoglobin level : 17.1 g/100 mL to supply the cells of the lungs themselves, not for oxygen exchange. Adult’s normal level : 11 g/ 100 mL 3. Specialized structures present in the fetus shunt 4. Newborn’s hematocrit : 53% blood flow to supply the most important organs Adult’s normal level : 45% of the body: the brain, liver, heart, and kidneys.  Change from fetal to adult hemoglobin levels begins  A neural plate (thickened portion of the before birth and accelerates after birth ectoderm) is apparent by the 3rd week of gestation. Its top portion differentiates into the neural tube – will form the central nervous system (brain and spinal cord), and the neural Respiratory System crest – will develop into the peripheral nervous system  3rd week of intrauterine life – respiratory and  8th week – brain waves can be detected on an digestive tracts exist as a single tube electroencephalogram (EEG)  Initially it is solid structure – then canalizes  All parts of the brain (cerebrum, cerebellum, (hollows out) pons, and medulla oblongata) form in utero, not  End of 4th week – a septum begins to divide the completely mature @ birth; growth proceeds esophagus from the trachea; lung buds appear on rapidly @ during the 1st year and continues @ the trachea high levels until 5 – 6 years of age  7th week of life – diaphragm does not completely  Eye and inner ear develop as projections of the divide the thoracic cavity from the abdomen original neural tube  If it fails to close completely, the stomach,  24 weeks – ears is capable of responding to spleen, liver, or intestines may enter the sound; eyes exhibit papillary reaction, indicating thoracic cavity sight is present  Child will be born w/ Diaphragmatic hernia or w/ intestine still present in the chest – compromising the lungs and perhaps displacing the heart Endocrine System  As soon as endocrine organs mature in intrauterine life, function begins, including the following processes:  Fetal adrenal glands supply a precursor for estrogen synthesis by the placenta  Important respiratory developmental milestones  Fetal pancreas produces the insulin needed by include the following: the fetus (insulin does not cross the placenta  Alveoli and capillaries begin to form bet. 24th from the mother to the fetus) and 28th weeks – both development must be  Thyroid and parathyroid glands play vital roles in complete before gas exchange can occur metabolic fxn and calcium balance  Spontaneous respiratory practice movements begin as 3 month’s gestation and continue throughout pregnancy  Specific lung fluid w/ a low surface tension Digestive System and low viscosity forms in alveoli to aid in  4th week – digestive tract separates from the expansion of the alveoli @ birth; rapidly respiratory tract absorbed after birth  Initially solid, tubes canalize (hollow out) to become  24th week (6 months) of pregnancy, alveolar patent; then, endothelial cells of GI tract proliferate cells secrete = Surfactant, a phospholipid extensively, occluding lumens, then canalize again substance; decreases alveolar surface  Proliferation of cells shed in the 2nd re-canalization tension on expiration, preventing alveolar forms the basis for meconium collapse and improving the infant’s ability to  6th week – abdomen becomes too small to contain maintain respirations in the outside the intestine and portion of it, guided by the viteline environment membrane (a part of the yolk sac), is pushed into the base of the umbilical cord – where it remains until  Components of surfactant: about the 10th week – when abdominal cavity has  Lecithin (L) grown large enough to accommodate all of the  Sphingomyelin (S) intestinal mass  As intestine returns to the abdominal cavity – it must rotate 180 degrees  Lack of surfactant is a factor associated w/ the  Failure to rotate = inadequate mesentery development of respiratory distress syndrome attachments = volvulus of the intestine in the newborn  Omphalocele – congenital anomaly; intestine coils and remains outside the abdomen Nervous System  Gastroschisis – occurs when the original midline fusion that occurred @ the early stage is  3rd to 4th weeks of life – active formation of the incomplete nervous system and sense organs  Meckel’s diverticulum – a pouch of intestinal  Requires vast quantity of glucose during this time – tissue results when the viteline duct does not embryo takes glucose – leaving mother w/ mild atrophy after return of the intestines hypoglycemia = dizziness, vomiting  Meconium – forms in the intestines as early as 16th weeks; collection of cellular wastes, bile,  fats, mucoproteins, mucopolysaccharides, and portions of the vernix caseosa (lubricating substance that forms on the fetal skin); sticky in  Testes 1st form in the abdominal cavity and do not consistency and appears black or dark green descend into the scrotal sac until the 34th – 38th week  Male preterm infants – born w/ undescended (obtaining its color from bile pigment) ▪ White meconium – sign of biliary testes; should be observed closely to be sure obstruction testes descend when child reaches what would have been the 34th – 38th week of gestational life – because testicular descent does not occur as  GI tract is sterile before birth readily in extrauterine life as it would in utero  Vit. K levels are low in newborns – it is synthesized by the action of bacteria in the Urinary System intestines  End of 4th week – rudimentary kidneys already  32 weeks’ gestation/ fetus weighs 1,500g – sucking present; do not appear essential for life before birth and swallowing reflexes are matured enough – placenta clears the fetus of waste products  36 weeks – GI tract is able to secrete enzymes  12th week – urine is formed and excreted thru the essential to carbohydrate and protein digestion amniotic fluid by the 16th week of gestation  3 mos after birth – amylase, enzyme found in  @ term, fetal urine is excreted @ the rate of 500 saliva, necessary for digestion of complex mL/day  Patent urachus – discovered @ birth; persistent starches, matures drainage of a clear, acid-pH fluid (urine) from the umbilicus –an open lumen bet. the urinary bladder  Liver is active throughout gestation – functions as a and the umbilicus failed to close filter bet. incoming blood and the fetal circulation, and as a deposit site for fetal stores such as iron and glycogen Integumentary System  Still immature @ birth = possibly leading to  Skin of a fetus appears thin and almost translucent hypoglycemia and hyperbilirubinemia – 2 until subcutaneous fat begins to be deposited @ serious problems in the 1st 24 hours after birth about 36 weeks  Lanugo – soft downy hairs covering fetal skin  Vernix caseosa – cheese-like substance, important for lubrication and for keeping the skin from Musculoskeletal System macerating in utero Immune System  11th week – Fetal movements visible on ultrasonography  Immunoglobulin G (IgG) – maternal antibodies;  Almost 20 weeks of gestation (5th month) – mother cross the placenta into the fetus during 3rd trimester feels the fetal movements (quickening) of pregnancy  1st 2 weeks of fetal life – cartilage prototypes provide  gives fetus temporary passive immunity against position and support diseases for w/c mother has antibodies:  12th week – ossification of bone tissue begins and  poliomyelitis continues until adulthood  rubella (German measles)  Carpals, tarsals, and sternal bones generally do  rubeola (regular measles) not ossify until birth is imminent  diphtheria  tetanus  infectious parotitis (mumps) Reproductive System  hepatitis B  Child’s sex is determined @ the moment of  pertussis (whooping cough) conception – by a spermatozoon carrying an X or a Y  little or no immunity to herpes virus (cold sores, chromosome; 8th week (thru chromosomal analysis) genital herpes) – average newborn is potentially  6th week of life – gonads (ovaries or testes) form susceptible to these diseases  If testes form = testosterone is secreted, influencing the sexually neutral genital duct to  IgA and IgM – cannot cross the placenta form other male organs (maturity of the wolffian, or mesonephric ducts)  Absence of testosterone secretion = female organs will form (maturation of müllerian, or paramesonephric duct)  If mother takes an androgen or androgen-like substance during this stage of pregnancy – child who is chromosomally female, would appear more male than female @ birth = musculinization in female infants  Pseudo-hermaphrodism or intersex – if deficient testosterone is secreted by the testes = both müllerian (female) duct and the male (wolffian) duct could develop  The Growing Fetus Chapter 9 ▪ Chorionic villi have a central core surrounded by Page 189 - 215 a double layer of trophoblast cells ▪ Outer of the 2 covering layers is termed the syncytiotrophoblast, or the syncytial layer ▪ Stages of Fetal Development ▪ Inner /Middle layer – cytotrophoblast or ▪ 38 weeks = fertilized egg (ovum) ➔ fully Langhan’s layer developed fetus ▪ Outer of the 2 covering layers is termed the syncytiotrophoblast, or the syncytial layer – instrumental in the production various placental ▪ Fetal Growth and Development typically hormones: divided into 3 periods: ▪ hCG (Human chorionic gonadotrophin) 1. Pre-embryonic – 1st 2 weeks beginning w/ ▪ Somatomammotropin (human placental fertilization lactogen [hPL]) 2. Embryonic - Weeks 3 - 8 ▪ Estrogen 3. Fetal – weeks 8 through birth ▪ Progesterone ▪ Fertilization, Conception, Impregnation, ▪ Inner layer – cytotrophoblast or Langhan’s layer Fecundation* ▪ Appears to function early in pregnancy ▪ Usually occurs at the outer third of to protect the growing embryo and fetus fallopian tube = ampulla from certain infectious organisms such ▪ usually only 1 ovum reaches maturity as the spirochete of syphilis each month ▪ Disappears bet. 20th and 24th week = syphilis not a threat before this time ▪ Fxnal life of spermatozoon ▪ Offers little protection viral invasion @ ▪ 42 hrs (possibly up to 72 hrs) any point ▪ Critical time span for (sexual relations must occur) successful fertilization? ▪ 72 hours (48hrs b4 ovulation + 24hrs after) ▪ The Placenta ▪ Fetal in origin EMBRYONIC AND FETAL STRUCTURES ▪ 15 – 20 cm in diameter, 2 – 3 cm in depth ▪ Serves as fetal lungs, kidneys, and GI tract, and as a separate endocrine organ ▪ The Decidua throughout pregnancy ▪ After fertilization, the corpus luteum in the ovary continues to function rather ▪ Placental Circulation than atrophying * ▪ 3rd week ▪ The uterine endometrium, instead of ▪ oxygen sloughing off as in a normal menstrual ▪ glucose osmose from the maternal cycle, continues to grow in thickness and ▪ amino acids blood thru the cell layers vascularity = DECIDUA ▪ fatty acids ▪ minerals of the chorionic villi to the ▪ Latin word for “falling off” villi capillaries ▪ vitamins ▪ Decidua has 3 separate areas: ▪ water ▪ Decidua basalis ▪ part of the endometrium that ▪ Placental Circulation lies directly under the embryo ▪ For practical purposes, there is no direct ▪ or the portion where the exchange of blood between the embryo trophoblast cells are and the mother during pregnancy* establishing communication w/ ▪ outer chorionic villi layer – only one cell maternal blood vessels thick ▪ Decidua capsularis ▪ Only a few substances are able to cross ▪ encapsulates the surface of the from the mother into the fetus trophoblast ▪ Almost all drugs are able to cross into ▪ Decidua vera fetal circulation ▪ the remaining portion of the ▪ woman should take no non-essential uterine lining drugs (including alcohol and nicotine) during pregnancy ▪ Chorionic Villi ▪ All of the specific mechanisms or ▪ After implantation trophoblast cell processes that allow nutrients to cross matures the placenta are affected by: ▪  ▪ Maternal blood pressure and ▪ 11th or 12th day – miniature villi ▪ pH of the fetal and maternal (probing “fingers”) plasma ▪  ▪ Chorionic villi ▪ As the # of chorionic villi increases w/ pregnancy ▪  ▪  ▪ At term almost 200 villi have formed  ▪ Villi form an increasingly complex into a separate, important HORMONE – communication network w/ the maternal blood PRODUCING system ▪  ▪ Intervillous spaces grow larger and larger ▪ WHAT HORMONES ARE PRODUCED BY THE ▪  SYNCYTIAL LAYER? ▪ Becoming separated by a series of partitions or 1. Human Chorionic Gonadotrophin (hCG) septa ▪ 1st hormone produced ▪  ▪ Can be found in maternal blood and ▪ Matured placenta – 30 separate segments or urine as early as the 1st missed ▪ cotyledons menstrual period (shortly after ▪  implantation has occurred) through ▪ These compartments make maternal side of the about 100th day (14th week) of placenta @ term look rough and uneven pregnancy ▪ Negative hCG in mother’s serum – w/in ▪ Placental Formation 1 – 2 weeks after birth ▪ 100 maternal uterine arteries supply the ▪ Testing for hCG can be used as proof that mature placenta* all of the placental tissue has been ▪ 1No additional maternal arteries appear delivered after the 1st 3 mos. of pregnancy ▪ Human Chorionic Gonadotropin (hCG)* ▪ 2mother’s heart rate, total cardiac ▪ Purpose: to act as a fall-safe measure to output, and blood volume  to supply ensure that the corpus luteum of the the placenta ovary continues to produce progesterone and estrogen1 Placental Circulation ▪ May also play a role in suppressing the maternal immunologic response^ ▪ In the intervillous spaces – maternal blood jets ▪ 8th week of pregnancy: outer layer of from the coiled or spiral arteries in streams or cells of the developing placenta begins spurts to produce progesterone – production ▪  of hCG begins to decrease at this point ▪ Maternal blood is then propelled from compartment to compartment by the currents 2. Estrogen initiated ▪ Primarily estriol ▪  ▪ “hormone of women” ▪ As blood circulates around the villi and nutrients ▪ Contributes to the mother’s mammary osmose from maternal blood into the villi gland development in preparation for ▪  lactation ▪ Maternal blood gradually loses its momentum ▪ Stimulates uterine growth to and settles to the floor of the cotyledons accommodate the developing fetus ▪  ▪ Blood enters the orifices of maternal veins 3. Progesterone located in the cotyledons ▪ “hormone of mothers” ▪  ▪ Blood is returned to maternal circulation ▪ Appears to reduce contractility of the uterine muscles during pregnancy preventing premature labor= The Placenta ▪ probably produced by a change in ▪ Braxton Hicks contractions electrolytes (potassium and calcium), ▪ present from about 12th weeks of w/c es contraction potential of the pregnancy uterus ▪ aid in maintaining pressure in the intervillous spaces by closing off uterine 4. Human Placental Lactogen ( hPL, Human veins momentarily w/ each contraction Chorionic Somatomammotropin) ▪ When mother lies on her LEFT SIDE ▪ w/ both growth-promoting and ▪ lifts the uterus away from the inferior lactogenic (milk-producing) properties vena cava1 ▪ produced by the placenta beginning the ▪ When mother lies on her BACK 6th week of pregnancy – increasing to a ▪ weight of the uterus compresses the peak level @ term vena cava ▪ promotes mammary gland growth in ▪ placental circulation can be sharply preparation for lactation in the mother* reduced = ▪ serves the important role of regulating ▪ SUPINE HYPOTENSION * maternal glucose, protein, and fat ▪ At term: placenta weighs 400 – 600 gms levels** (1lb.) or 1/6 the weight of the baby ▪ Diabetic woman - fetus may develop a larger than usual placenta Placental Proteins ▪ Placenta also produces several plasma Endocrine Function proteins* ▪ may contribute to decreasing the ▪ Syncytial (outer) layer of chorionic villi – serves immunologic impact of the growing as source of oxygen and nutrients, and develops placenta  ▪ provides a circulatory pathway that The Amniotic Membranes connects the embryo to the chorionic villi of the placenta ▪ The chorionic villi on the medial surface of ▪ Functions: the trophoblast* ▪ to transport oxygen and ▪ begins to gradually thin, leaving the medial nutrients to the fetus from the surface of the structure smooth placenta and ▪ chorion leave, or smooth chorion ▪ to return waste products from ▪ Smooth chorion eventually becomes the the fetus to the placenta chorionic membrane - ▪ 53 cm (21 inches) in length (@ term) ▪  ▪ 2 cm (3/4 inch) thick ▪ Once it becomes smooth, it offers support to ▪ What is the bulk of the cord called?* the sac that contains the amniotic fluid ▪ A gelatinous mucopolysaccharide ▪  ▪ Wharton’s jelly ▪ 2nd membrane lining the chorionic ▪ outer surface – covered w/ amniotic membrane = the amniotic membrane or membrane amnion forms beneath the chorion ▪ the remnant of the yolk sac may be ▪ the amniotic membranes not only offers found in the fetal end of the cord – as a support to amniotic fluid but also actually white fibrous streak @ term produces the fluid* = Phospholipid ▪ The Amniotic Fluid ▪ Contains how many veins and arteries? ▪ constantly being newly formed and ▪ 1 vein* reabsorbed by the amniotic membrane * ▪ 2 arteries* ▪ reabsorbed @ the rate of 500 mL/24 hours ▪ # of veins and arteries in the cord is ▪ some of it is probably absorbed by direct always assessed and recorded @ birth: contact w/ the fetal surface of the placenta ▪ major method of absorption occurs because ▪ 1% - 5% of all infants are born w/ a cord that contains a single vein and artery fetus continually swallows the fluid ▪ Amount @ term? - 800 – 1200 mL ▪ Rate of blood flow thru an umbilical cord is rapid ➔ 350 mL/min @ term* ▪ Method of absorption: ▪ Percutaneous umbilical blood sampling (PUBS) ▪ Fetus swallows amniotic fluid ▪  ▪ blood is withdrawn from the umbilical ▪ From the fetal intestine, it will be absorbed into vein or transfused into the vein during the fetal bloodstream intrauterine life for fetal assessment or ▪  treatment ▪ Goes to the umbilical arteries ▪ Nuchal cord ▪  ▪ loose loop of cord around fetal neck; ▪ To the placenta ▪ 20% of all births ▪  ▪ oxygen supply is not impaired ▪ And it is exchanged across the placenta ▪ The Umbilical Cord ▪ If fetus is unable to swallow (esophageal atresia ▪ Walls of the umbilical cord arteries are or anencephaly) = lined w/ smooth muscle ▪ Hydramnios – >2,000 mL* ▪ Constriction of these muscles after birth ▪ When fetal kidneys become active = urine contributes to hemostasis and helps adds to the quantity of the amniotic fluid** prevent hemorrhage of the newborn ▪ Oligohydramnios (