MCB 135e

Midterm 2 Review

November 3, 2006

Midterm 2

• Wednesday, November 812:10 – 1:00 p.m.

• Covers material from Labor and Delivery on 10/6/06 to Growth and Endocrinology (II) on 11/3/06– Development of the Nervous System

(Part 3) will be covered on final

Format of Exam

• Same as Midterm 1

– Multiple Choice (30 points)

– True/False (20 points)

– Short Answer (50 points)

Sections covered on exam

• Labor and Delivery• Cardiorespiratory Changes after Birth• Infant at Risk• Thermoregulation• Lactation• Gastrointestinal Function• Liver• Development of Kidney Function/Kidney and Acid-

Base Balance• Growth and Growth Patterns• Growth & Endocrinology (I and II)

Labor and Delivery

• Parturition– birth of the baby

– a biological and social event

– Delivery 38 weeks after fertilization or 40 weeks after last menstrual period

• Mechanism of onset of labor not completely understood– Mechanical and hormonal factors are important

Hormones Involved in Labor

• Fetal Hormones– Corticotropin Releasing Hormone (CRH)– Adrenocorticotropic Hormone (ACTH)

• Placental Hormones– Estrogen (E)– Progesterone (P)– Prostaglandins

• Maternal Hormones– Oxytocin– Relaxin (produced by ovary and also placenta)

Fetal Hormones

• Corticotropin Releasing Hormone (CRH)– Secreted by hypothalamus

• Adrenocorticotropic Hormone (ACTH)– Secreted by anterior pituitary

• Cortisol– Secreted by adrenal cortex– Stimulates Estrogen secretion from placenta– Inhibits Progesterone secretion

Placental and Maternal Hormones

• Increased E secretion and decreased P secretion, leads to:– High E:P ratio– Uterine contractions, because:

• E stimulates contractions• P inhibits contractions

• Contractions stimulate the maternal hypothalamus to secrete Oxytocin

• Oxytocin further stimulates contractions

Prostagladins and Relaxin• Prostagladins

– Released from the placenta– Stimulated by E and oxytocin– Stimulates oxytocin and promotes

contractions

• Relaxin– Produced by corpus luteum of the ovary– Loosens ligaments and softens cervix– Increases number of oxytocin receptors

Cardiorespiratory Changes after Birth

• Transition from prenatal to postnatal life– Must be rapid– Requires critical changes in pulmonary

and circulatory systems• Expansion of lungs for first breath• Closure of ductus venosus, ductus

arteriosus, and foramen ovale• Removal of fluid from lungs

Closure of Foramen Ovale

• Results from pressure change in atria– Increased pulmonary blood flow

increases pressure in LA

– Pressure in left heart greater than right (after birth)

– Also, decreased flow from placenta to IVC

Closure of Ductus Arteriosus

• Results from reduced pulmonary resistance– Pulmonary pressure falls and equals

aortic pressure

– Lack of pressure gradient reduces blood flow through DA, causing it to shut

Fetal Lung Fluid

• Composed of amniotic fluid and fluid secreted by the lungs itself

• Chloride ion drives fluid into potential airspace of lungs– Generates pressure to stretch the lungs and

stimulate growth

• Function of the fluid:– Important for growth and specialization of lung

components prior to birth– Influences lung resistance

Removal of Fetal Lung Fluid

• Absorption of Na+ ion at birth switches lung’s capacity to an absorptive state

• Membrane of lungs switches from predominantly Cl- secreting to predominantly Na+ absorbing– Reverses flow of fluid in the lungs– Fluid exits the interstitial space via the

lymphatic ducts and microcirculation

Infant at Risk• Fetal Distress

– Low oxygen• Meconium aspiration

– Fetal bowl content discharged at birth that could be inhaled and block airways

• Sepsis – Blood poisoning

• Congenital anomalies• Maternal Diseases• Toxins• Premature birth

Thermoregulation

• Process of regulating body temperature

• Environment, vascular and metabolic adaptations, shivering and sweating are various ways in which adults regulate body temp.

• Newborns and infants have reduced capability of regulating body temp.

Thermoregulation in Newborns/Infants• Primarily occurs through Non-shivering Thermogenesis• Exposure to cold stimulates hypothalamus

• Norepinephrine (NE) is released and stimulates receptors on brown fat cells

• Triglycerides are broken down into fatty acids and glycerol through the action of lipase– Fatty acids broken down (oxidized) in mitochondria of

BFC– Uncoupling protein leads to heat production instead of

ATP

• Also, leads to conversion of T4 to T3 – Increased metabolic rate leads to increased body heat

production

Mechanisms of Heat Loss• Conduction

– Transfer of heat from one solid body to another

• Convection– Transfer of heat from a solid to the surrounding

gas or liquid

• Evaporation– Air passing over body evaporates water on

surface and removes heat– Largest source of heat loss in infants

• Radiation– Exchange of infrared (IR) photons with

surroundings– Heat is gained/lost depending on temp. gradient

Lactation

• Survival and growth of an infant depends on:

– Mother’s ability to breastfeed

– Baby’s ability to suck

– Proper development/function of GI system

– Proper development/function of CNS

Witches’ Milk and Colostrum• Witches’ Milk

– Baby secretes milk few days after birth under the influence of maternal estrogen

– Occurs in full-term infants, not pre-mature• Estrogen levels may not be high enough for pre-mature

infants

• Colostrum– First milk that precedes the production of true milk– Yellowish in color– Rich in antibodies and minerals– High in carbohydrates, proteins, but no fat

Milk Production• Stimulated by the hormone Prolactin

(PRL)– Secreted by anterior pituitary gland

– Levels of PRL increase 20 fold during pregnancy

– However, its action is inhibited by high E and P levels

– Therefore, milk production is suppressed until birth (except for small amount of colostrum)

Milk Production (after birth)

• Once the levels of E and P decrease, milk is produced.

• With each feeding, secretion of PRL is stimulated.

Milk Ejection

• Stimulated by the hormone Oxytocin

– Suckling stimulates hypothalamus to release oxytocin from posterior pituitary

– Oxytocin increases contraction of myoepithelial cells around the ducts• Forces milk out of alveoli and into the large

ducts (sinuses) and then out the nipple

Benefits of Breastfeeding

• Infant– Reduction in infections– Initial increased growth– Decreased obesity in adulthood– Positive effects on mental development

• Mother– Rapid weight loss– Decreased risk of breast cancer– Psychological benefits

Breastfeeding Not Always Ideal

– Maternal illness

– Stress

– Inadequate milk production

– If drugs and toxins are taken by mother

– Increased risk of HIV transmission

Gastrointestinal Function• Major functions

– Digestion and absorption

– Defense• Biochemical and immunologic mechanisms

– Endocrine• Hormones that regulate GI secretion and motility

– Mechanical and chemical mechanisms• Break-down of food, propulsion of food along GI tract,

excretion of feces, enzymatic reactions, transport reactions

Increased Risk of Dehydration• Smaller size of organs of GI system in

early postnatal development

• Food contents are liquid, so rapid transit– Shorter duration of food in stomach and

throughout GI system– Reduced rate of digestion/absorption– Reduced water reabsorption of intestinal

mucosa

• Proteins used for growth and development– Very little urea is excreted

• A byproduct of proteins• Produced in liver• Helps reabsorb water in the kidneys

Liver• Complex functions of digestion and

body growth– Formation of bile– CHO storage and release– Formation of urea– Metabolism of cholesterol– Manufacture of plasma proteins– Regulation of fat metabolism– Metabolism of some hormones– Reduction and conjugation of steroid hormones– Vitamin D metabolism– Detoxification of drugs/toxins

Jaundice• Caused by high levels of bilirubin in blood

• Begins with breakdown of RBCs

• Heme from Hb is broken down to bilirubin

• Bilirubin enters liver

• Conjugation of bilirubin to form a water soluble product and secretion into bile

• Conjugated bilirubin excreted in feces

• Jaundice occurs when bilirubin is not excreted and instead accumulates in the blood

Kidney • Major functions:

– Regulation of water and electrolytes

– Maintenance of pH

– Excretion of waste and byproducts of metabolism

– Secretion of hormones• Erythropoietin• Renin• Vitamin D3

Functions of Hormones

• Erythropoietin– Increases the number of RBCs so there is better

oxygen transport (Hematopoiesis – increased formation of RBCs)

• Renin– Involved in the secretion of angiotensin– Secreted by juxtaglomerular apparatus of kidneys

in response to low blood volume or low body NaCl

• Vitamin D3– Important for calcium metabolism, by increasing

calcium absorption in the intestine

Hormones that Regulate Kidney Function

• AldosteroneDecreased blood pressure/Low blood flow to kidneys

Release of Renin from JGA of kidneys

AngiotensinogenAngiotensin I Angiotensin IIStimulation of Adrenal CortexAldosterone Secretion

ACE = Angiotensin Converting Enzyme

Function: Aldosterone leads to increased salt and water retention by kidneys

ACE

Hormones that Regulate Kidney Function

• Antidiuretic Hormone (ADH or vasopressin)

– Secreted by hypothalamus

– Stored and released from posterior pituitary

– Acts on loop of Henle, distal tubules, collecting ducts

– Function:» Stimulates cAMP and increases number of

water channels» Increases water reabsorption

Risk of Dehydration in Infants• Skin – Greater water loss through skin (increased

surface area)

• GI Tract – Less mature, faster transit so less time for water reabsorption

• Kidney – malformations at 5 developmental stages, less urea, shorter loop of Henle (less water through medulla)

• Posterior Pituitary – Less ADH Secreted, less sensitivity of cells that line collecting duct

• Adrenal Cortex – less aldosterone

Changes in Urinary pH in Premature Infants

• First week of life– pH tends to be more alkali (pH 6-7)

• Second week of life– pH much more acidic (pH 5)

– Maintenance of pH difficult in newborns (esp. premature infants)• Kidneys not fully developed• Systems are less efficient

Growth

• Increase in an organism’s size and weight

• Reflection of how well you are (all other systems of body must be functioning properly for growth to occur)

• Occurs when anabolic processes predominate over catabolic processes

Anabolic: simple substances converted to complex compounds

Catabolic: complex substances converted to simple compounds

Factors that Affect Growth• Prenatal Period

– Genetic factors

• Environmental factors– Availability of nutritional substances– Parental age– Parity (amount of time between

successive childbirths)– Multiple births– Fetal sex

Changes in proportion of human body during growth

Comparison of Kwashiorkor and Marasmus

Kwashiorkor: West African, means “disease that occurs when displaced from the breast by another child.” Major pathology: protein deficiency

Marasmus: Progressive emaciation due to diet deficient in all calories & nutrients

Catch-up growthCatch-up growthMalnutrition and severe disease cause

• Growth retardation

However

Establishment of adequate nutrition and recovery from illness

• Induces growth rate acceleration until individual growth patterns and normalcy in

terms of chronologic age are restored.

Malnutrition and severe disease cause• Growth retardation

However

Establishment of adequate nutrition and recovery from illness

• Induces growth rate acceleration until individual growth patterns and normalcy in

terms of chronologic age are restored.

Compensatory GrowthCompensatory Growth

• Growth that usually follows the loss of an organ or part of an organ or tissue

• Examples:• Cellular hypertrophy (increase in SIZE of cell) as in

growth of muscle• Increase in contralateral kidney size when one kidney

is removed• Increase in size (hypertrophy and hyperplasia) in

response to increased functional demand (e.g., adrenal enlargement during stress)– Hyperplasia: increase in NUMBER of cells

• Growth that usually follows the loss of an organ or part of an organ or tissue

• Examples:• Cellular hypertrophy (increase in SIZE of cell) as in

growth of muscle• Increase in contralateral kidney size when one kidney

is removed• Increase in size (hypertrophy and hyperplasia) in

response to increased functional demand (e.g., adrenal enlargement during stress)– Hyperplasia: increase in NUMBER of cells

Reminder

• No discussion section on Monday, Nov. 6

• My office hours on Monday:– 9:10 – 10:00 a.m. Free Speech Café– 1:10 – 2:00 p.m. 105 GPB

• Bring pen and pencil to exam