Physiology

Question 1

What happens in the proliferation phase of uterine cycle?

Answer 1

Estrogen stimulates development of uterine lining;
Endometrial layer grows 3-5 fold, 8-10mm
Endometrial glands enlarge
Spiral arteries elongate
Smooth muscle layer thickens due to mitogenic action of estrogen
Upregulation of estrogen and progesterone receptors

Question 2

What happens in the secretory phase of the uterine cycle?

Answer 2

Endometrium prepares itself for implantation;
Endometrium maintained by progesterone => further growth inhibited
Spiral arteries elongate & coil -> blood supply increases
Progesterone promotes differentiation of secretory cells
Glands enlarge and produce uterine milk (glycogen rich fluids)

Question 3

What is semen composed of?

Answer 3

Spermatozoa (<10%)
15-150 million/mL

Seminal Vesicle Fluid (60%)
Fructose & other nutrients
Fibrinogen to clot semen
prostaglandins to stimulate uterus
Ejaculated last

Prostate gland secretions (20%)
PSA- prostrate specific antigen= a protease to break down clotted sperm
Alkaline, milky & thin
Acid phosphatase to activate sperm

Bulbourethral gland secretions (~10%)
Mucoproteins- neutralise urine & lubricate urethra
Pre-ejaculate (mostly are devoid of sperm as it is released before ejaculation

Question 4

Functions of amniotic fluid

Answer 4

Insulation against trauma
Allows symmetrical growth
stops amnion sticking to fetus
important for lung development
Enables fetal limb respiratory movement
Enables swallowing (important for gut development)
helps maintain constant body temp
potential source of fluid & electrolytes
Immunoprotection- for fetus: innate immune system proteins found in amniotic fluid, for mother: vaginal flushed with clean liquid

Question 5

How does fluid enter the amniotic cavity?

Answer 5

Fetal urine (dilute)
Lung liquid (isosmotic with plasma)- important for lung growth

Question 6

Differences in fetal and adult cardiovascular FUNCTION

Answer 6

varying oxygen tension in fetuses (constant in adults) as vessels above ductus arteriosus have greater oxygen tension than vessels below DA. 
Combined cardiac output (CCO) high
Blood pressue low
fast HR
Kidneys only get 2-3% of CCO
Pulmonary bed has high resistance, rest enters aorta via DA
Blood oxygenated in the placenta
most blood bypasses liver via DV

Question 7

carrier of glucose to fetus

Answer 7

GLUT-!

Question 8

Fetal factors affecting growth

Answer 8

Genetic- chromosomal abnormalities, single gene, males larger, race, height/weight of parents
Hormones- insulin, IGF1, IGF2 (insulin-like growth factor)
Infection- CMV, rubella

Question 9

Maternal factors affecting growth

Answer 9

Maternal constraint (size)
Number of fetuses
Age
Parity
Nutrition
Disease eg. hypertension
Uterine abnormalities
Site of implantation
Smoking/alcohol/drugs

Question 10

Placental factors affecting growth

Answer 10

TRUE placental insufficiency affects growth after 7th month bc placental capacity well in excess of fetal requirements before then
weight of placenta affected by growth factors?- weight of fetus 6x placenta weight

Question 11

How is fluid removed from the lungs after birth?

Answer 11

1. expelled through baby’s mouth from trachea
2. absorbed by pulmonary blood vessels
3. absorbed in pulmonary lymphatics

Question 12

Pulmonary vasculature dilates after birth due to:

Answer 12

1. reduction in lung expansion
2. ventilation
3. high PO2 of air

Question 13

Why does the foramen ovale close?

Answer 13

1. Decrease in venous return via IVC

2. Increase in venous return from pulmonary veins

Question 14

stimuli for constriction of DA

Answer 14

high PO2
decrease in BP thru lumen since less BF in it
decrease in circulating PGE2
decrease in PGE2 receptors in DA wall

Question 15

4 main adaptations to extrauterine life

Answer 15

1. Removal of placenta circulation
2. Closure of umbilical vein and DV
3. Increase in pulmonary BF
4. Closure of foramen ovale