Anatomy and Physiology Pregnancy, Growth, and Development Martini’s Visual Anatomy and Physiology First Edition Martini w Ober Chapter 26 Pregnancy, Growth, and Development Lecture 24 80 min (39 slides)

Review for Lab Exam 2 (See Study Guide) Respiratory (8 questions) Be able to calculate vital capacity, minute volume Review and understand what you did in lab, the equipment you used to derive your data, and understand the results of your breathing experiments Recognize structures in your study guide on the torso models or in photographs Urinary System (16 questions) Be able to recognize all the structures, including all parts of the nephron and the adrenal glands (know these structures well!!) [torso, plaque models, individual models, photos] Review your urinalysis lab/results and be sure to understand what you did in lab (specific gravity, Clinistix, etc)

Review for Lab Exam 2 Reproductive (torso,isolated models) (4 questions) Be able to recognize the major reproductive structures for the male: testes, epididymis, ductus deferens, seminal vesicles, prostate Be able to recognize the major reproductive structures for the female: ovaries, fallopian tubes, uterus, vagina, ligaments *Endocrine (photo, torso model) (2 questions) Be able to recognize major endocrine organs Cat Dissections (photo, cadaver) (18 questions) Know the cardiovascular system well and be able to recognize the vessels, using either a cat or a photograph of a cat. Be able to recognize major structures listed on your Lab guide using either a cat or a photograph of a cat.

Lecture Overview Prenatal times and terminology Major events of each trimester Fertilization, implantation, and development Hormonal changes during pregnancy Labor and delivery Milk Production Postnatal period

Pregnancy, Growth, and Development Pregnancy (gestation) is the presence of a developing offspring in the uterus - About 38-42 weeks (9 months) in length - Divided into trimesters (about 3 months each) - Called the ‘prenatal’ (before birth) stage of development Growth is an increase in size. Involves increases in cell numbers (hyperplasia) and cell sizes (hypertrophy) Development is the continuous process by which an individual changes from one life phase to another - Prenatal (development in utero) - Neonatal (first 28 days after birth) - Postnatal (from birth until maturity) - Aging and death

Prenatal Terminology and Times Week Embryological (week 1 to 8) Fetal (week 9 to birth) 1st trimester 2nd trimester 3rd trimester 1-12 Prenatal Development (38-42 weeks) 13-25 26-38 Date of conception – add 14 days to the date of the onset of the last menstrual period Preembryonic stage is considered to span 0 – 16 days after fertilization. (0-30h, zygote; 30-72h, cleavage; 3-4 days, morula; 4-16 days, blastocyst) Due Date – add 266 days to the date of conception (about 280 days from the onset of the last menstrual period) (Rule of thumb from onset of last menstrual period: Subtract 3 months from the month of the last period, then add 4 days unless pregnancy covers an entire month of February, then add 7 days)

Major Events in Each Trimester First trimester (weeks 1-12) Most critical period (most vulnerable to drugs, alcohol) Embryological and early fetal development Rudiments of all major organ systems appear Second trimester (weeks 13-24) Development of organs and organ systems (almost complete by end of sixth month) At end of trimester, fetus looks human Third trimester (weeks 25 to birth) *Rapid fetal growth Deposition of adipose tissue Major organ systems become functional At 35 weeks: (~2.5 Kg), fetus can usually survive if born early (twins typically born during this time)

Steps in Fertilization Figure from: Hole’s Human A&P, 12th edition, 2010 sperm cell reaches corona radiata of egg acrosome releases enzymes sperm cell penetrates zona pellucida sperm cell’s membrane fuses with egg cell’s membrane Fresh sperm have a tough membrane stiffened by cholesterol. Fluids in the female reproductive tract leach cholesterol from membrane so head of sperm becomes more permeable (last part of capacitation – about 10 hrs.) Sperm are viable for up to 6 days after ejaculation. Two acrosomal enzymes: hyaluronidase (breaks apart granulosa cells of corona radiata), and acrosin breaks through the z. pellucida of ovum. Prevention of polyspermy (fertilization by more than one sperm – fatal) is prevented by: fast block (binding of sperm opens Na+ channels in egg membrane inhibiting attachment of any more sperm), and a slow block (cortical granules release secretion below z. pellucida creating a fertilization membrane between egg and z. pellucida). Fertilization by more than one sperm (polyspermy) is prevented by a fast block and a slow block.

Early Human Development – Pre-embryonic Figure from: Hole’s Human A&P, 12th edition, 2010 Takes about 72 hours for an egg to reach the uterus after ovulation. Cleavages: 1) increase S:V that favors nutrient uptake and waste removal 2) produces larger number of cells to form different embryonic tissues Preembryonic stage is considered to span 0 – 16 days after fertilization. (0-30h, zygote; 30-72h, cleavage; 3-4 days, morula; 4-16 days, blastocyst) Monozygotic (identical) twins: embryoblast divides in half and share a placenta; dizygotic (fraternal) twins; two (or more) eggs ovulated and fertilized, each has its own placenta

Implantation begins about the 6th day of development trophoblast will help form the placenta trophoblast secretes hCG - suppresses menstruation by maintaining the corpus luteum Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Summary of Stages and Events of Early Human Prenatal Development fertilized ovum 12-24 hours after ovulation zygote forms cleavage 30 hours to third day mitosis increases cell number morula third to fourth day solid ball of cells blastocyst fifth day through second week trophoblast and inner cell mass form gastrula end of second week primary germ layers form

Early Embryonic Stage Gastrula stage Three primary germ layers form Figure from: Hole’s Human A&P, 12th edition, 2010 Gastrula stage Three primary germ layers form 2 weeks (~2mm long)

Primary Germ Layers Figure from: Hole’s Human A&P, 12th edition, 2010 Ectoderm – Nervous system, some sensory organs, epidermis, hair, nails, glands of the skin, linings of the mouth and anal canal. Mesoderm – all muscle, bone, bone marrow, blood, blood vessels, lymphatic vessels, internal repro organs, kidneys, mesothelium of body cavities. Endoderm – eipithelial lining of digestive tract, respiratory tract, urinary bladder, urethra. All three layers retain some stem cells, which persist in the adult.

Changes During Embryonic Development Figure from: Hole’s Human A&P, 12th edition, 2010

Changes During Embryonic Development Figure from: Hole’s Human A&P, 12th edition, 2010 End of eighth week marks end of embryological period

Embryonic Membranes Figure from: Hole’s Human A&P, 12th edition, 2010 As amnion develops, it surrounds the embryo, and the umbilical cord begins to form from structures in the connecting stalk

Functions of the Placenta Mnemonic for placental functions: IRENE Immune Respiratory Endocrine Nutritional Excretory Table from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Placenta Placental membrane consists of Figure from: Hole’s Human A&P, 12th edition, 2010 Placental membrane consists of epithelial wall of an embryonic capillary epithelial wall of a chorionic villus

Placenta at Seventh Week Figure from: Hole’s Human A&P, 12th edition, 2010 Consists of an embryonic portion and a maternal portion

Overview of Fetal Circulation Gases and nutrients are exchanged with the fetus through the placenta. Breathing and digestion are carried out by the mother for the fetus. Besides the umbilical vessels, the major differences in fetal circulation are due to the fact that: Fetal lungs are collapsed; fetus is not breathing air There is nothing to digest; fetus is not eating Let's get an overview of the fetal circulation and review some important concepts from previous lectures.   Recall that we've already talked about the five main roles of the placenta and introduced the mnemonic, IRENE, to help you remember those functions. Two of those roles, respiration and nutrition, are relevant to our topic today. In terms of respiration, O2 diffuses from the mother’s blood to the placenta in order to oxygenate the fetal blood, and also allows CO2 to diffuse from the fetus’ circulation to the placenta to be taken away and handled by the mother’s circulation. With regard to its nutritional role, the placenta allows transfer of nutrients to the fetus. These nutrients have been ingested by the mother, absorbed by her digestive system, and processed by her liver before entering the fetal circulation. These would include the major nutrients we talked about in our nutrition and metabolism lectures. Q: What are some of the most important nutrients we discussed? Ans: glucose, amino acids, fatty acids, vitamins and minerals. So, it should be clear from these two roles of the placenta that the fetus does not need to breathe to obtain O2 or eliminate CO2, nor does it need to ingest food to obtain the nutrients required for its growth and development. Okay, with that background, let’s take a look at the general circulation of the fetus. First, keep in mind that when we are talking about the fetal circulation, the designations of arteries and veins are with respect to the fetus’ circulatory system. As we discussed when we talked about the adult circulation, arteries always carry blood away from the heart, veins always bring blood back to the heart – regardless of their oxygenation status. As you can see in the slide, a portion of the arterial blood moving away from the heart is brought to the placenta via the TWO umbilical arteries (about 50-60% of abdominal aortic blood), which are branches of the internal iliac arteries. Notice that there are two umbilical arteries, one coming from each of the two internal iliac arteries. Blood returned from the placenta (about 80-85% O2 saturated) is carried back to the fetal circulation via the single umbilical vein, a structure we will discuss further in a couple of minutes. Notice how the coloration of the vessels on the slides corresponds roughly to the level of oxygenation of the blood: red being highly oxygenated and blue being least oxygenated. You can see that the aorta is carrying oxygen-rich (about 67% saturated) blood from the heart, while the vena cavae are returning oxygen-poor blood from the fetal tissues to the heart. You’ll also notice a third, purplish, color on some of the vessels in the slide depicting the level of oxygenation of the blood in the abdominal aorta. (Blood leaving placenta is about 80% saturated.) There is mixing of oxygenated blood returning from the placenta and deoxygenated blood returning through the vena cavae from fetal tissues (about 30% oxygenated). This blood has a level of oxygenation somewhere between (about 60%) that contained in the those two vessels. With that overview, let’s first review the circulation in and around the mature heart and then move on to the specific circulatory modifications of the fetus in more detail…. Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Pathway of Blood Through Heart Remember that in the normal adult, venous/deoxygenated blood from the inferior and superior vena cavae, along with blood from the coronary sinus, enters the right atrium. It then passes into the right ventricle, through the pulmonary trunk and into the pulmonary arteries and is oxygenated in the lungs. Recall that this is the pulmonary circulation.   The oxygenated blood returns from the lungs via the pulmonary veins to the left atrium, then to the left ventricle, and then enters the systemic circulation via the aorta. As we discussed previously, each ventricle of the mature heart sends its output to a different circulation (known as an in-series type of circulation). Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Modifications in Fetal Pulmonary Circulation 1 2 Figure from: Martini, & Ober, Visual Anatomy & Physiology, Pearson Science, 2012 Now let's examine the changes in the pulmonary circulation of the fetus that allow most of the blood coming from the heart to bypass the collapsed fetal lungs.   Remember that the fetus is not breathing air, there is no air in the lungs so there are no gases to exchange, and the fetal alveoli and pulmonary vessels are collapsed. Think about the need for sending blood to the fetal lung alveoli in the same way as we thought about ventilation-perfusion matching (or coupling) when we looked at the adult pulmonary circulation. If there’s no oxygen to be transported from an area of the lung, then we don’t need to send large amounts of blood to that area. Analogously, since the fetal lungs do not contain oxygen in the collapsed alveoli, no blood needs to be sent through the pulmonary capillaries to be oxygenated. So where does the fetus' O2 come from if it's not breathing? Right, the blood returning from the placenta via the umbilical vein contains all the oxygen the fetus needs, and the pulmonary circulation can be bypassed entirely. The two anatomical structures that bypass the fetal lungs, called shunts, are numbered on this slide. They include the foramen ovale and the ductus arteriosus. The foramen ovale allows much of the mixed blood from the umbilical vein and the fetal inferior vena cava to bypass the right ventricle and pass directly into the left atrium (a right-to-left inter-atrial shunt) and then pass directly into the left ventricle. Some blood returning to the right atrium, especially from the SVC, enters the right ventricle. The ductus arteriosus allows most of the blood that has gotten into the right ventricle to bypass the pulmonary arteries and pass from the pulmonary trunk directly into the last part of the aortic arch. The net effect of these anatomical shunts is that the blood returning to the fetal heart has bypassed the pulmonary circulation almost entirely, and BOTH ventricles are effectively sending all of their output to the systemic circulation. Because both ventricles are essentially part of the systemic circulation in the fetus is, the fetal cardiac output is termed the Combined Ventricular Output (CVO) or Combined Cardiac Output (CCO). Ductus venosus 1. Foramen ovale – allows blood returning to right atrium to bypass right ventricle and pass directly into left atrium (then to lt. ventricle, then aorta) 2. Ductus arteriosus – allows blood from right ventricle to bypass pulmonary trunk and pass directly into the aorta

Modifications in Fetal Digestive Circulation 1 Now let’s take a look at the changes in the fetal circulation that relate to the pathway of nutrients and the fetal circulation around the liver.   Remember that the fetus is not eating, so there food to be digested and absorbed by the infant’s digestive system and no nutrients be processed by the developing fetal liver. The mother’s digestive system and liver have already done these things for the fetus. In fact, the fetal liver is not yet capable of performing many of the metabolic functions it will eventually perform after birth. However, as in the case of the lungs, it still needs some supply of blood in order to continue its development. As you'll also note in this slide, the hepatic portal vein is still bringing venous blood from the fetal abdominal structures to the liver and supplies some of the blood needed for liver development. You can also see that about 50% of the blood from the umbilical vein bypasses the liver through the ductus venosus and goes directly to the inferior vena cava and returns to the heart. Figure from: Shier et. al., Hole’s Human Anatomy & Physiology, McGraw-Hill, 2010 1. Ductus venosus – allows about 50% of blood returning to fetus through the umbilical vein to bypass the liver and empty directly into the inferior vena cava (then back to rt. atrium of heart)

Changes in Fetal Circulation After Birth Foramen Ovale -> Fossa ovalis Ductus Arteriosus -> Ligamentum arteriosum Ductus Venosus -> Ligamentum venosum Umbilical vein -> Ligamentum teres Umbilical arteries -> Medial umbilical ligaments (and superior vesical arteries to urinary bladder) Obviously, after birth the newborn must now carry out respiration and ingestion of food on its own and this will require changes to the fetal circulation to allow the newborn to adapt to life outside the uterus.   This slide shows a side-by-side comparison of the fetal circulation on the left, and the circulation shortly after birth on the right. The functional changes to the fetal circulation occur within hours after birth. Decreasing levels of O2, increasing CO2, cold, and tactile stimulation stimulate the newborn to take its first breath – a major event that begins to alter the fetal pulmonary circulatory pattern. (Although structural changes are not complete until after several months to a year after birth.) Decreased pressure in the pulmonary vessels due to lung expansion cause the pressure in the right atrium to drop, while pressure in the left atrium rises due to increased return of blood from the lungs. The pressure in the left atrium becomes higher than that in the right atrium and this holds the formen ovale against the interatrial septum, preventing flow of blood from the left atrium to the right atrium. After the flap of tissue heals structurally over the course of months to a year or so, a depression called the fossa ovalis remains in place of the closed foramen ovale. (In about 20-25% of people, the foramen ovale remains unsealed and is held in place mainly by the higher pressure in the left ventricle but this is usually of no consequence unless there is an elevation of left atrial pressure, e.g., pulmonary hypertension.) Changes in the pulmonary circulation also cause pressure to drop in the pulmonary trunk and rise in the aorta. (aorta fetal 30 mm Hg; aorta newborn 100 mm Hg) Because of this blood initially begins to flow backwards from the aorta through the ductus arteriosus and into the pulmonary trunk, which exposes the vessel to higher levels of O2, resulting in constriction. Lower levels of prostaglandins in the newborn than those in the fetus cause further constriction and collapse of the ductus arteriosus. After about 3 months, the ductus arteriosus permanently closes and becomes the ligamentum arteriosum, a fibrous cord of tissue connecting the pulmonary trunk to the aorta. The modifications to the foramen ovale and ductus arteriosus functionally eliminate the pulmonary shunts and divide the circulatory pattern of the heart into a pulmonary and systemic circulation. Finally, after the umbilical cord is clamped, the umbilical vein closes, and for a few hours most of the portal blood continues to flow though the ductus venosus into the IVC. After this, the ductus venosus contracts effectively closing the pathway from the portal vein to the IVC. Blood from the hepatic portal vein now flows into and through the liver and then to the IVC via the hepatic veins. A portion of the umbilical arteries closest to the internal iliac arteries, remains to supply some of the urinary bladder (as the superior vesical arteries). The rest of the umbilical vessels become fibrous cords or ligaments, as you can see in the slide. It is not known what causes closure of the ductus venosus, Figure adapted from: Tortora, Principles of Anatomy & Physiology, Wiley Press, 2002

Congenital Cardiovascular Problems Right-to-left shunt Left-to-right shunt -> Pulmonary hypertension, pulmonary edema, and cardiac enlargement (Congenital = Present at Birth) Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Congenital Cardiovascular Problems Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Hormonal Changes During Pregnancy Mechanism that preserves uterine lining during early pregnancy hCG helps prevent spontaneous abortion

Hormonal Changes During Pregnancy Relative concentrations of three hormones in maternal blood during pregnancy Secreted mainly by placenta after about 12 weeks Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Hormonal Changes During Pregnancy Hormone Source Effect Human Chorionic Gonadotropin Placenta Maintains corpus luteum until week 12 Estrogen/Progesterone Corpus luteum/ placenta Stimulate and maintain uterine lining, inhibit FSH and LH, inhibit uterine contractions, and enlarge reproductive organs Relaxin (Possible: Causes pelvic ligaments to relax, widen, and become flexible); inhibits uterine contractions; promotes uterine blood vessel growth Human Chorionic Somatomammotropin (also Placental Lactogen) Mammary gland development; glucose-sparing effect in mother; weak GH-type effect Human Chorionic Thyrotropin Increases size/activity of maternal thyroid and parathyroid glands Aldosterone Adrenal cortex Increases fluid retention In humans, relaxin may syngergize with progesterone to stimulate decidual cells in early pregnancy and aid in growth of blood vessels in the pregnant uterus.

The Fetus and Mother at Term Changes during pregnancy: Digestive: Morning sickness (causes ? High levels of hormones, adaptation to protect from toxic foods); constipation, heartburn, 15% rise in BMR, increased appetite; demand for nutrients especially high in last trimester, more than mother can take in – placenta stores nutrients early in pregnancy and releases later. Circulatory: Maternal blood volume rises 30% during pregnancy (fluid retention + incr hematopoiesis) – gives extra 1-2 L of blood; pressure of uterus on large pelvic vessels interferes with venous return from legs and pelvic region (hemorrhoids, varicose veins, edema of feet). Respiratory system – Minute ventilation increases about 50% (oxygen demands about 20% higher and progesterone increases sensitivity of chemoreceptors to CO2); expanding uterus prevents full breaths so respiratory rate increases while depth of breathing decreases; late in pregnancy, pelvis may expand enough to allow fetus to ‘drop’ and take some pressure off diaphragm. Urinary system – Aldosterone and steroids of pregnancy increase water/Na retention; glomerular filtration increases about 50% and urine output is slightly elevated; pressure of uterus on bladder reduces its capacity and causes frequency and some leakage (incontinence). Integumentary system – Dermis stretches to accommodate uterine growth and increase fat stores (may cause striae or reddish stretch marks that usually disappear after pregnancy; melanocyte activity increases causing some areas to become darker, e.g., areola and linea alba (now called linea nigra); some experience temporary darkening of skin over nose and cheeks (chloasma, mask of pregnancy) Uterine growth – Uterus weighs about 50 g with no fetus; by term it weighs about 900 g; growth is monitored by palpating the fundus which eventually almost reaches the xiphoid process. Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

The Fetus and Mother at Term Changes during pregnancy: Digestive: Morning sickness (causes ? High levels of hormones, adaptation to protect from toxic foods); constipation, heartburn, 15% rise in BMR, increased appetite; demand for nutrients especially high in last trimester, more than mother can take in – placenta stores nutrients early in pregnancy and releases later. Circulatory: Maternal blood volume rises 30% during pregnancy (fluid retention + incr hematopoiesis) – gives extra 1-2 L of blood; pressure of uterus on large pelvic vessels interferes with venous return from legs and pelvic region (hemorrhoids, varicose veins, edema of feet). Respiratory system – Minute ventilation increases about 50% (oxygen demands about 20% higher and progesterone increases sensitivity of chemoreceptors to CO2); expanding uterus prevents full breaths so respiratory rate increases while depth of breathing decreases; late in pregnancy, pelvis may expand enough to allow fetus to ‘drop’ and take some pressure off diaphragm. Urinary system – Aldosterone and steroids of pregnancy increase water/Na retention; glomerular filtration increases about 50% and urine output is slightly elevated; pressure of uterus on bladder reduces its capacity and causes frequency and some leakage (incontinence). Integumentary system – Dermis stretches to accommodate uterine growth and increase fat stores (may cause striae or reddish stretch marks that usually disappear after pregnancy; melanocyte activity increases causing some areas to become darker, e.g., areola and linea alba (now called linea nigra); some experience temporary darkening of skin over nose and cheeks (chloasma, mask of pregnancy) Uterine growth – Uterus weighs about 50 g with no fetus; by term it weighs about 900 g; growth is monitored by palpating the fundus which eventually almost reaches the xiphoid process. Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Factors Contributing to Onset of Labor as birth approaches, progesterone levels decrease (allowing increase in uterine contractions); estradiol continues to rise prostaglandins synthesized which may initiate labor stretching uterine tissue stimulates release of oxytocin oxytocin stimulates uterine contractions fetal head stretches uterus, cervix, vagina, and vulva positive feedback results in stronger and stronger contractions and greater release of oxytocin Over course of gestation, uterus exhibits relatively weak Braxton Hicks contractions that become stronger in late pregnancy (and may cause women to think they are in labor – false labor). These contractions become much more powerful at term (labor contractions), marking the beginning of parturition. Levels of progesterone (inhibitory for uterine contractions) decline slightly after about 6 months, while estrogen levels (stimulate contractions) continue to rise and contributes to irritability of the uterus later in pregnancy. Also, OT is released toward the end of pregnancy: 1. stimulates smooth muscle of uterus 2. stimulates fetal membranes to secrete prostaglandins). Labor is prolonged if either OT or PG is lacking and may be sped along by administering OT. Fetal cortisol rises late in pregnancy and may stimulate estrogen secretion. Fetal pituitary also secretes OT, which may stimulate fetal membranes to secrete PGs. Uterine stretching increases contractility (may be the reason twins are born earlier). In the vertex position, fetal head pushes against the cervix which is especially sensitive to stretch.

Birth Process A positive feedback mechanism propels the birth process Figure from: Hole’s Human A&P, 12th edition, 2010 Labor contractions progress from about 30 min apart to 1-3 minutes apart. Since each contraction reduces fetal blood flow, intermittent nature of contractions is important. Contractions are strongest in the fundus and weakest in the cervix, tending to push fetus downward.

Stages of Labor Stages of labor: 1. Dilation 2. Expulsion 3. Placental Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Parturition = process of giving birth Stages of labor: 1. Dilation 2. Expulsion 3. Placental Normal position of fetus just prior to delivery (cephalic, vertex presentation) Breech presentation is bottom first

Stages in Birth dilation (1st) stage - onset of true labor - variable in length (8 hrs. or more) - contraction up to ½ minute every 10-30 min - Rupture of amniotic membrane (“water breaks”) late in process Time for this stage is usually less in multipara (given birth before) than it is in a primipara (first time giving birth). Cervix dilates and effaces, and fetus begins moving toward cervical canal Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Stages in Birth expulsion (2nd) stage - usually less than 2 hrs - contractions at max intensity (lasting for 1 min, every 2-3 min) Abdominal muscle contraction plus Valsalva manuver aid in expulsion. Pain of labor due to: 1) ischemia of myometrium at first and 2) stretching of cervix, vagina, and perineum later. If tearing of vaginal tissue is likely to be a problem, an episiotomy may be performed. Pain of human childbirth compared with other animals is a product of evolution: 1) unusually large head and brain of human and 2) narrowing of pelvic outlet which helped hominids adapt to bipedal locomotion. Can last typically 30-60 minutes in a primipara, and as little as 1 minute in a multipara. Crowning – top of baby’s head is visible, stretching the vulva. Cervix is pushed open by approaching fetus (positive feedback cycle) and baby’s head enters vagina Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Stages in Birth placental (3rd) stage - afterbirth - usually within an hour after delivery About 30 mL of blood lost during this stage, but uterine contractions compress blood vessels and prevent more extensive bleeding. Careful inspection of the afterbirth is required to be sure everything is expelled, since anything left behind can cause postpartum hemorrhage. Also, the umbilical vessels are counted since an abnormal number of vessels may indicate cardiovascular abnormalities in the infant. Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Milk Production placental estrogens and progesterone stimulate further breast development estrogens cause ductile system to grow progesterone causes alveolar glands to develop placental lactogen (HCS) also produces changes in breast prolactin is released about the 5th week of pregnancy milk production does not begin until after birth Lactation can last for as little as 1 week in women who do not nurse, but it can last for many years in women who continue to nurse or use a mechanical device to extract milk. (Median time for nursing is about 2.8 years worldwide.) Progesterone stimulates development of acini (glands) at ends of ducts in breast tissue. Colostrum is main secretion in breasts in late pregnancy and about 1-3 days postpartum. Colostrum is similar to breast milk in terms of protein and lactose content, but contains 1/3 as much fat and a high proportion of maternal ab, especially IgA. Prolactin at full term is about 10-20 times normal levels, but has relatively little effect on breasts until after birth. The breasts are mainly prepared for lactation by the steroids of pregnancy, which generally antagonize prolactin and inhibit milk synthesis. Once the level of these steroids drops after birth, prolactin begins to stimulate milk production. Milk synthesis also requires GH, cortisol, insulin, and PTH. After the birth of the infant, prolactin surges (10-20 times normal levels) for a couple of hours after the infant nurses and then returns to normal levels. Only 5-10% of women become pregnant when nursing, perhaps due to inhibition of GnRH. This may be an evolutionary adaptation designed to space births out more evenly. In women who do not nurse, their reproductive cycle resumes in a few weeks but they are usually anovulatory for the first 6 months following birth.

Milk-Letdown Reflex Recall that oxytocin (OT) is a stimulus for smooth muscle contraction and is secreted by the neurohypophysis OT stimulates myoepithelial cells in the walls of the lactiferous ducts and sinuses Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Nipple and areola are invested heavily with sensory nerves. It takes about 30-60 seconds for the infant to get any milk, then milk fills the ducts and lactiferous sinuses and is easily drawn out. Know this pathway

Ejection of Milk Figure from: Hole’s Human A&P, 12th edition, 2010

Human Colostrum, Breast Milk, and Cow’s Milk Table from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Cow’s milk is not a good substitute for human milk: 1) higher protein forms harder ‘curd’ in infant’s stomach so it’s not digested and absorbed as readily and it also increases nitrogenous waste excretion (may increase incidence of diaper rash); 2) does not provide the laxative effect to clear meconium from infant’s digestive tract. (Since a large part of this is bile, this may help decrease the incidence of jaundice); 3) does not provide ab protection to infant, and; 4) does not help colonize the infant’s GI tract with beneficial bacteria. Mother nursing one infant produces about 1.5 L/day. Nursing is equivalent to losing 50 g of fat, 100 g of lactose (from glucose), and 2-3 g of Ca. The Ca helps ossify the infant’s cartilagenous skeleton during the first year postpartum. If a mother’s intake of dietary Ca and vitamin D is insufficient during pregnancy, PTH production is stimulated and the Ca needed for the infant is taken from the mother’s bones.

Postnatal Period Neonatal period birth to end of 6th week newborn begins to carry on respiration, obtain nutrients ingest nutrients, excrete wastes, regulate body temperature, and make cardiovascular adjustments Infancy 5th week to one year growth rate is high teeth begin to erupt muscular and nervous systems mature communication begins First 6 weeks postpartum = puerperium (return of mother to normal physiology)

Postnatal Period Childhood Adolescence one year to puberty growth rate is high permanent teeth appear muscular control is achieved bladder and bowel controls are established intellectual abilities mature Adolescence puberty to adulthood person becomes reproductively functional and emotionally more mature growth spurts occur motor skills continue to develop intellectual abilities continue to mature

Postnatal Period Senescence Adulthood old age to death degenerative changes continue body becomes less able to cope with demands placed on it death results from various conditions and diseases Adulthood adolescence to old age person remains relatively unchanged anatomically and physiologically degenerative changes begin

THE END!!!!

Review Week Embryological (week 1 to 8) Fetal (week 9 to birth) 1st trimester 2nd trimester 3rd trimester 1-12 Prenatal Development (38-42 weeks) 13-25 26-38 Date of conception – add 14 days to the date of the onset of the last period Due Date – add 266 days to the date of conception (about 280 days from the onset of the last menstrual period) Know this slide and the terms on it - Postnatal (from birth until maturity) - Neonatal (first 28 days after birth) - Infancy (end of 4th week to one year) - Childhood (1 year of age to puberty) - Adolescence (puberty to adulthood) - Senescence (decline of sex hormones; old age to death)

Review First trimester Second trimester Third trimester Critical period (most vulnerable) Embryological and early fetal development Rudiments of all major organ systems appear Second trimester Development of organs and organ systems (almost complete by end of sixth month) At end of trimester, fetus looks human Third trimester Rapid fetal growth Deposition of adipose tissue Major organ systems become functional

Review Hormone Source Effect Human Chorionic Gonadotropin Placenta Maintains corpus luteum until week 12 Estrogen/Progesterone Corpus luteum/ placenta Stimulate and maintain uterine lining, inhibit FSH and LH, inhibit uterine contractions, and enlarge reproductive organs Relaxin Causes pelvic ligaments to relax, widen, and become flexible; inhibits uterine contractions; promotes uterine blood vessel growth Human Chorionic Somatomammotropin (also Placental Lactogen) Mammary gland development; glucose-sparing effect in mother; weak GH-type effect Human Chorionic Thyrotropin Increases size/activity of maternal thyroid and parathyroid glands Aldosterone Adrenal cortex Increases fluid retention