Fallopian Tubes and Uterus

Question 1

ovulated ovum

Answer 1

Ovulated ovum is captured by the fimbriae of the fallopian tubes. The paired fallopian tubes, also known as the oviducts or uterine tubes, are tubular organs connecting the ovary with the uterus
The ovum is then transported towards the uterus, along the length of the fallopian tubes
The uterus is a pear-shaped muscular organ located in the pelvic cavity, with thick muscular walls
It is the site where a potential embryo is implanted

Question 2

fallopian tubes

Answer 2

Provide a suitable environment for gamete transport, gamete maturation, fertilization, and early embryo development. More specifically, the fallopian tubes catch the ovulated secondary oocyte, nourish the oocyte, provide the microenvironment for fertilization, and transport the embryo undergoing cleavage to the uterus

Question 3

fallopian tube structure

Answer 3

Each fallopian tube is approximately 10 cm long, and has four segments: the infundibulum, ampulla, isthmus, and the intramural region

Question 4

infundibulum

Answer 4

a funnel shaped distal segment with finger like projections called fimbriae, which are responsible for capturing the ovum from the ovary

Question 5

ampulla

Answer 5

the longest and most expanded region where fertilization normally occurs

Question 6

isthmus

Answer 6

the narrow segment adjacent to the uterine wall

Question 7

intramural

Answer 7

the uterine or intramural part passes through the wall of the uterus and opens into the uterus

Question 8

histological organization of the fallopian tube walls

Answer 8

the wall of the fallopian tube has three layers: the serosa, muscularis, and mucosa

Question 9

fallopian wall serosa

Answer 9

forms the outer covering

Question 10

fallopian wall muscularis

Answer 10

contains an inner circular and outer longitudinal smooth muscle layer. Estrogen stimulates oviductal secretion and muscle contraction, whereas progesterone reduces oviductal secretion and contraction of smooth muscle

Question 11

fallopian wall mucosa

Answer 11

fallopian tubes are lined with simple columnar epithelium consisting of ciliated columnar cells and non-ciliated secretory cells. Their nutritive secretory product frequently protrudes into the lumen prior to release
○ The lamina propria is the CT layer of the mucosa underlying the epithelium
○ The mucosa is folded throughout the tubes. The mucosal folds are largest and most numerous in the ampulla, decreasing in size toward the uterus

Question 12

the uterus

Answer 12

pear shaped muscular organ divided into three regions:
1. body
2. fundus
3. cervix

Question 13

uterine wall layers

Answer 13

perimetrium: the outer CT layer which is adventitial in some areas, but largely serosa

myometrium: thick tunic of highly vascularized smooth muscle

endometrium: the mucosal lining of the uterus, divided into the stratum functionalis and stratum basalis

Question 14

the endometrium

Answer 14

The mucosal lining of the uterus, and consists of simple columnar epithelium supported by a lamina propria. Endometrium contains simple branched tubular uterine glands extending from the luminal surface into the lamina propria, which is made up of dense irregular CT

Question 15

endometrium regions

Answer 15

The endometrium can be subdivided into 2 regions:
1. The stratum functionalis: the more superficial layer, which undergoes profound changes during the menstrual cycle
The stratum basalis: the deeper layer adjacent to the myometrium. The stratum basalis remains relatively unchanged during menstruation

Question 16

arterial supply to the endometrium

Answer 16

The stratum functionalis is supplied by helical (spiral) arteries.
- The helical arteries are subject to hormonal control by progesterone. Withdrawal of progesterone renders the helical arteries ischemic, resulting in degeneration of mucosa and arteries
The stratum basalis is supplied by straight arteries. Straight arteries are not subject to hormonal control, and remain intact and functional even with a withdrawal of progesterone

The helical and straight arteries are branches of the arcuate arteries, which are located in the myometrium
These ultimately branch from the paired uterine arteries

Question 17

the myometrium

Answer 17

The thickest tunica of the uterus, consisting of bundles of smooth muscle fibres. It is composed of three poorly defined smooth muscle layers:
- The thin inner and outer layers are mostly longitudinal and oblique
- The middle layer is predominantly circular and contains abundant arcuate arteries
During pregnancy, the myometrium goes through a period of extensive growth involving both hypertrophy (cell growth) and hyperplasia (cell division; increase in the number of smooth muscle cells)

This well developed myometrium contracts very forcefully during parturition to expel the infant from the uterus. After pregnancy, uterine smooth muscle cells shrink and many undergo apoptosis

Question 18

the perimetrium

Answer 18

The outermost layer of the uterus consisting of two types of coverings; a serosa and an adventitia
- The fundus of the uterus is covered by serosa, which is a single layer of mesothelium resting on a thin layer of CT
- The body of the uterus is covered by an adventitia of CT. It is continuous with the peritoneal layer of the broad ligament of the uterus

Question 19

cyclical endometrial changes

Answer 19

From puberty until menopause at about ages 45-50, pituitary gonadotropins produce cyclic changes in ovarian hormone levels, which cause the endometrium to undergo cyclic modifications during the menstrual cycle
- The duration of the menstrual cycle may be variable but averages 28 days
The cyclic structural changes occur gradually and the activities characterizing these phases overlap to some extent

Question 20

phase 1: premenstrual or ischemic stage

Answer 20

Occurs at days 26-28 of the menstrual cycle. The helical arteries constrict periodically, triggered by the reduction of progesterone. As a result, hypoxia and anoxia occur in the stratum functionalis. The helical arteries then become permanently constricted and the glands cease to secrete
The stratum functionalis becomes ischemic (deprived of blood) resulting in an invasion by leukocytes, ischemia, and eventually necrosis of the stratum functionalis
In this phase, the endometrium shrinks and necrotic tissue is obvious

Question 21

phase 2 menstrual phase

Answer 21

Occurs between days 1-5 of the cycle. During this phase, there is ischemia, degeneration, and shedding of the stratum functionalis; the entire stratum functionalis breaks up and is discharged
The detached epithelium, uncoagulated blood, glandular secretions, and degenerating cells are discharged into the uterine cavity as menses
The stratum basalis remains intact because straight arteries are unaffected by hormonal changes. Basal cells of the glands in the stratum basalis begin to proliferate in the late menstrual phase. Newly formed cells migrate to the surface for regeneration of a new functional layer
- This phase demonstrates sloughing of the functional zone until only the basal zone remains

Question 22

phase 3: proliferative (follicular) phase

Answer 22

Occurs during days 6-14 of the cycle. The endometrium regenerated from the stratum basalis under the influence of estrogen. A new epithelial lining is formed in the thin endometrium. As a result, the stratum functionalis thickens and the glands lengthen. The glands are relatively straight, narrow, and empty
- The functional layer is fully restored by day 14 of the cycle
No evidence of spiral arteries

Question 23

phase 4: secretory (luteal) phase

Answer 23

Occurs from days 15-28 of the cycle. During this time, major changes occur in the stratum functionalis but the basal layer remains unchanged.
The helical arteries reach full development and become more coiled. The uterine wall continues to thicken; progesterone from the corpus luteum causes edema of the lamina propria and endometrium reaching maximal thickness
The uterine glands become highly convoluted and branched. As day 28 approaches, the glands cease to secrete. The stratum functionalis becomes ischemic and a new menstrual phase begins thereafter
- Spiral arteries are readily identifiable and glands become secretory
Around day 24, pre-decidual cells appear