CASE 13 HISTOPHYSIOLOGY

Question 1

What are the stages of the uterine cycle?

Answer 1

Menses, Proliferative, Secretory, and Ischemic stages.

Question 2

How thick is the endometrial lining during the peak of the secretory phase?

Answer 2

The endometrial lining is around 5-7 mm thick.

Question 3

What triggers the onset of menses?

Answer 3

Menses begins when there is no embryo implantation, leading to the degeneration of the corpus luteum.

Question 4

How is the ovulated oocyte captured for fertilization?

Answer 4

The oviduct’s fimbriated ends capture the oocyte to facilitate fertilization.

Question 5

What happens to the ovarian follicle after ovulation?

Answer 5

The remaining follicle wall forms the corpus luteum, which secretes hormones to prepare the uterus.

Question 6

During which phase of the menstrual cycle does ovulation occur?

Answer 6

Ovulation typically occurs around day 14 of a 28-day menstrual cycle

Question 7

What is the purpose of the blastocyst hatching?

Answer 7

Hatching exposes trophoblast cells to interact with the uterine wall for implantation.

Question 8

Which enzymes facilitate blastocyst hatching?

Answer 8

Enzymes secreted by trophoblast cells break down the zona pellucida.

Question 9

How does the uterine lining prepare for implantation?

Answer 9

The uterine lining develops an extracellular matrix to facilitate embryo attachment.

Question 10

What role do pinopodes play in implantation?

Answer 10

Pinopodes from endometrial cells help interact with trophoblast microvilli to aid embryo attachment.

Question 11

What hormone-like proteins are involved in embryo attachment?

Answer 11

Heparin-bound epidermal growth factor-like proteins (HB-EGF) in endometrial cells interact with EGF receptors on trophoblast cells.

Question 12

How does the endometrial stroma change during decidualization?

Answer 12

Stromal cells accumulate glycogen and lipids, swell, and begin to secrete decidual prolactin.

Question 13

How do trophoblast cells invade the endometrial lining?

Answer 13

Trophoblast cells penetrate intercellular spaces, assisted by a reduction in desmosomes between endometrial cells.

Question 14

What process remodels the primary decidual zone?

Answer 14

Metalloproteinases (MMPs) remodel the primary decidual zone.

Question 15

Why is immune response suppressed during implantation?

Answer 15

Immune suppression is achieved by leukocytes in the endometrium, which secrete interleukin-2 (IL-2) to prevent the maternal immune system from attacking the embryo, which is recognized as a foreign body due to its paternal antigens.

Question 16

What are the two layers of the trophoblast during implantation?

Answer 16

The trophoblast differentiates into two layers: the cytotrophoblast, which is a cellular layer, and the syncytiotrophoblast, which is a multinucleated syncytial layer. Together, these layers aid in anchoring the embryo and forming the placenta.

Question 17

What is the function of chorionic villi?

Answer 17

Chorionic villi are structures that grow from the trophoblast into the uterine wall, where they come in close contact with maternal blood vessels. These villi allow nutrient and gas exchange between the mother and fetus.

Question 18

How do syncytiotrophoblast cells support pregnancy hormonally?

Answer 18

Syncytiotrophoblast cells secrete several key hormones, including human chorionic gonadotropin (HCG), which sustains the corpus luteum, and human chorionic somatomammotropin, estrogen, and progesterone, all of which help maintain the endometrial lining and support pregnancy.

Question 19

What marks the transition from primary to secondary villi?

Answer 19

The transition occurs when extraembryonic mesoderm invades primary villi, creating a core within each villus. This core is surrounded by cytotrophoblast and syncytiotrophoblast layers, forming secondary villi.

Question 20

How are tertiary villi formed?

Answer 20

Tertiary villi are formed when embryonic blood vessels grow into the secondary villi, making them vascularized. This vascularization enables efficient nutrient and gas exchange with maternal blood.

Question 21

What happens to maternal blood around the tertiary villi?

Answer 21

Maternal blood fills the intervillous spaces surrounding the tertiary villi, allowing direct contact with fetal capillaries within the villi for nutrient, gas, and waste exchange.

Question 22

How does the placenta support fetal-maternal blood flow?

Answer 22

Maternal spiral arteries bring oxygen-rich blood into the intervillous spaces, where fetal blood in chorionic villi absorbs nutrients and oxygen. Deoxygenated blood is returned to maternal circulation via maternal veins.

Question 23

Which hormone signals early pregnancy and is detected in tests?

Answer 23

Human chorionic gonadotropin (HCG) is detected in pregnancy tests. It is produced by the syncytiotrophoblast and supports the corpus luteum, which secretes progesterone to maintain the endometrial lining.

Question 24

How does the placenta regulate maternal immune response?

Answer 24

Cytotrophoblast cells produce FAS ligand, which interacts with immune cells to prevent maternal immune rejection of the fetus, protecting the pregnancy.

Question 25

What is the luteal-placental shift in pregnancy, and why is it important?

Answer 25

The luteal-placental shift occurs around the end of the first trimester when the placenta takes over the production of progesterone and estrogen from the corpus luteum. This shift is crucial for maintaining the pregnancy as these hormones support the endometrial lining and inhibit uterine contractions.

Question 26

How does maternal blood volume change during pregnancy, and why?

Answer 26

Maternal blood volume increases by approximately 50% to ensure adequate blood flow to the placenta and fetus. This change is driven by increased maternal oxygen demands and to support fetal growth.

Question 27

What are the respiratory changes that occur in pregnancy?

Answer 27

During pregnancy, both respiratory rate and tidal volume increase to provide extra oxygen to the fetus and to remove excess carbon dioxide from the maternal and fetal blood.

Question 28

What hormonal changes initiate milk secretion after childbirth?

Answer 28

After childbirth, a drop in progesterone and estrogen levels (as the placenta is no longer present) allows prolactin to stimulate milk production in the mammary glands.

Question 29

What is the milk ejection reflex, and what hormone drives it?

Answer 29

The milk ejection reflex, or “let-down” reflex, is driven by oxytocin. When a baby suckles, oxytocin is released, causing the smooth muscles around milk ducts to contract and release milk.

Question 30

How is prolactin regulated during nursing?

Answer 30

Prolactin release from the pituitary gland is stimulated by suckling, which overrides prolactin inhibitory hormone (dopamine) and increases milk production. This is a neuroendocrine reflex response to ensure milk supply during breastfeeding.

Question 31

What happens to mammary tissue after lactation ends?

Answer 31

After lactation, the breast undergoes involution. Secretory epithelial cells are removed by apoptosis, ducts remodel, and lobules significantly decrease, leading to reduced breast volume.

Question 32

How does the breast change during menopause?

Answer 32

During menopause, breast tissue undergoes further involution. Glandular epithelium and connective tissue are replaced by adipose (fat) tissue, reducing the number of ducts and lobules.

Question 33

What cellular changes occur during breast involution?

Answer 33

Involution involves proteolytic degradation of basement membranes, stromal remodeling, and a decrease in lobules and acini while the ductal system remains relatively unchanged.

Question 34

How does breast tissue change during the menstrual cycle?

Answer 34

Breast tissue undergoes cyclical changes, including increased stromal edema, vacuolization of myoepithelial cells, and greater mitotic and apoptotic activity. These changes are driven by fluctuations in estrogen and progesterone levels.

Question 35

What changes are observed in breast tissue during the late luteal phase?

Answer 35

In the late luteal phase, there is increased edema, stromal infiltration by immune cells, and a more prominent distinction between epithelial and myoepithelial cell layers.

Question 36

What happens to myoepithelial cells during the menstrual cycle?

Answer 36

Myoepithelial cells show vacuolization and increased activity during the menstrual cycle, particularly in the luteal phase, as they respond to hormonal changes.

Question 37

What hormones drive the growth of breast tissue during pregnancy?

Answer 37

Estrogen and progesterone drive the growth of mammary tissue during pregnancy, causing ductal epithelium to proliferate and secretory acini to expand in preparation for milk production.

Question 38

How does prolactin affect mammary glands during pregnancy?

Answer 38

Prolactin stimulates the secretory acini to start producing colostrum, although high levels of progesterone and estrogen prevent full milk secretion until after birth.

Question 39

What cellular infiltrates are found in breast tissue during pregnancy?

Answer 39

During pregnancy, breast tissue contains lymphocytes, eosinophils, and plasma cells within the intralobular stroma, preparing the gland for lactation and providing immune support.

Question 40

How do progesterone and estrogen levels change after birth to allow lactation?

Answer 40

After birth, progesterone and estrogen levels drop due to the absence of the placenta, which removes the inhibition on prolactin, allowing full milk production to commence.

Question 41

What changes occur in the breast tissue structure during lactation?

Answer 41

The breast tissue becomes mostly composed of expanded acini filled with milk. These acini are separated by thin connective tissue septa, and lipid droplets are visible within the milk.

Question 42

How is milk composition affected by cellular changes in the lactating breast?

Answer 42

Milk is rich in nutrients and contains lipid droplets formed in the acini, with secretions appearing eosinophilic (pink-staining) due to protein and lipid content.

Question 43

What triggers the milk ejection reflex?

Answer 43

The milk ejection reflex is triggered by suckling, which stimulates oxytocin release. Oxytocin causes contraction of myoepithelial cells around ducts, expelling milk from the mammary glands.

Question 44

How does suckling influence prolactin levels?

Answer 44

Suckling overrides dopamine (prolactin inhibitory hormone), leading to an increase in prolactin release from the pituitary gland, which supports continuous milk production.

Question 45

What psychological effects does oxytocin have on the mother during breastfeeding?

Answer 45

Oxytocin promotes bonding between mother and child, reduces stress, and enhances relaxation during breastfeeding, contributing to maternal-child attachment.

Question 46

What happens to the mammary glands when breastfeeding ends?

Answer 46

After weaning, the breast undergoes involution, where secretory epithelial cells undergo apoptosis and phagocytosis, leading to shrinkage and remodeling of mammary tissue.

Question 47

How does stromal tissue change after weaning?

Answer 47

Stromal tissue undergoes proteolytic degradation and remodeling, and the breast returns to a more pre-lactation-like state with reduced glandular tissue.

Question 48

Is the ductal system affected by breast involution?

Answer 48

The ductal system remains relatively unchanged, although the number of lobules and acini decreases significantly after lactation.

Question 49

What happens to the breast at menopause?

Answer 49

During menopause, breast tissue undergoes extensive involution. The glandular and ductal structures reduce dramatically, and adipose tissue replaces much of the glandular tissue.

Question 50

How does intralobular stroma change post-menopause?

Answer 50

The intralobular stroma is replaced by dense collagen, resulting in a firmer but less glandular breast structure.

Question 51

What changes occur in the breast’s glandular epithelium during menopause?

Answer 51

Glandular epithelium regresses, leaving mostly fatty tissue and collagen in place of functional lobules and ducts.

Question 52

How do mammary glands develop in infancy?

Answer 52

In infancy, mammary glands consist of basic mammary buds and rudimentary ducts within connective tissue stroma. This early structure is the foundation for future breast development.

Question 53

What hormonal changes drive mammary gland development during puberty?

Answer 53

Estrogen and progesterone promote ductal and lobular growth, with increased branching and terminal lobule formation, making the breast more complex and preparing it for potential lactation.

Question 54

What structural changes occur in mammary tissue at puberty?

Answer 54

The duct system expands, branches proliferate, and terminal lobules (acini) begin to form, with more adipose tissue accumulating in the breast.

Question 55

How are mammary glands organized anatomically?

Answer 55

Mammary glands are organized into 15–25 lobes, each consisting of smaller lobules made up of acini. Each lobe drains into a lactiferous duct that leads to the nipple.

Question 56

What is the function of the lactiferous sinus?

Answer 56

The lactiferous sinus is an expanded part of the lactiferous duct near the nipple, where milk accumulates during lactation before being ejected.

Question 57

What role does the areola play in lactation?

Answer 57

The areola surrounds the nipple and contains sebaceous glands that secrete lubricating oils, which protect the skin during breastfeeding.

Question 58

How does the inactive breast structure appear histologically?

Answer 58

In an inactive breast, the branching duct system is sparse, surrounded by dense fibrous interlobular tissue and adipose tissue. Ducts and acini are lined by epithelial and myoepithelial cells.

Question 59

What are the two layers lining the ducts and acini in inactive breast tissue?

Answer 59

The ducts and acini in inactive breast tissue are lined by two layers: an inner layer of epithelial cells adjacent to the lumen, and an outer basal layer of flattened myoepithelial cells that contain high concentrations of actin microfilaments.