Ga - Early Human Development Iii - Bilaminar Disc, Implantation And Ectopic Pregnany

Front 1

Fertilization --> Blastocyst (Intermediates)

Back 1

-Fertilization -> Cleavage -> Blastula -> Blastomeres -> Morula (compaction) -> Blastocyst -> Occurs while surrounded by zona pellucida

Front 2

Blastocyst Pathway

Back 2

-Cleavage and blastocyst formation occurs on way to uterus
-Blastocyst hatches
-Blastocyst implants in wall of uterus
-Blastocyst secretes proteins that degrade zona pellucida -> Implantation

Front 3

Human Chorionic Gonadotropin (hCG) - what is it secreted by, what are its 2 subunits, pregnancy tests

Back 3

-Secreted by STB (trophoblast)
-hCG has alpha- and beta-subunits; alpha-subunit common to several hormones, beta-subunit unique to hCG
-Pregnancy tests accurate within 7 days of fertilization via sensitive RIA (radioimmunoassay) for blood beta-hCG
-Home test kits less sensitive colorimetric assays- soon after missed period, can detect beta-hCG in urine

Front 4

If Fertilization Occurs, what happens to hCG and STB

Back 4

-STB becomes source of hCG
-hCG stimulates continued progesterone secretion by Corpus Luteum
-No menses (menstrual flow)
-First missed period and pregnancy

Front 5

Changes in the Uterine Mucosa

Back 5

-Early developing follicles secrete estrogen that support growth in thickness of endometrium lining, length of glandular endometrium, thickening of blood vessels
-Ovulation: remnants of ovarian follicle become corpus luteum which secrete progesterone and continue glandular and vessel elongation and increase sensory activity of the endometrium
-Implanted embryo: source of HcG – feeds back to maternal bloodstream which stimulates ongoing growth for hospital environment of embryo

Front 6

If No Fertilization Occurs, what happens to hCG and corpus luteum

Back 6

-No hCG
-Corpus luteum regresses, progesterone falls
-Menses occur

Front 7

The pituitary gland secretes gonatropins (hormones) of LH and FSH - what does each affect

Back 7

FSH - Maturation of follicle and ovulation
LH - Maturation of follicle, ovulation, and corpus luteum

Front 8

Implantation - Blastocyst pathway and resulting formations (2)

Back 8

-Blastocyst (loosens the matrix and cause degeneration of zona pellucida) hatches from Zona Pellucida (fibrous mixture of glycoproteins)
-Blastocyst attaches at pole containing inner cell mass
-Outer trophoblastic cells proliferate and fuse to form outer syncytium
-Results in formation of Inner Cytotrophoblast (CTB) and superficial Syncytiotrophoblast (STB)

Front 9

Syncytium and its components' functions

Back 9

-Large mass of cytoplasm containing nuclei of many cells formed by fusion of many uninucleate cells -> merge and form tissue layers:
-Cytotrophoboast (CTB): function is to attach the baby to the mother's uterus. It provides the anchor
-Syncytiotrophoblast (STB): persist up to placenta (respiratory/waste exchange for fetus)
-Both are part of trophoblast

Front 10

Implantation - Role of STB (LOOK AT SLIDES 13-15)

Back 10

-STB is an Invasive, motile layer
-STB breaks down endometrial epithelium and degrades stroma
-Maternal Blood Vessels open, bathing STB
-STB continues to invade and expand, forming irregular surface with Lacunae (bathed by RBC) = surface irregularities


STB: highly mobile, sends out projections into CT; causes rupture of blood vessels so that maternal blood is pouring onto STB surface
o Meanwhile STB is also burrowing into and degrading the wall of female reproductive tract
o Developing system closely attached with maternal blood vessels -> source of nutrients, food, oxygen and expels fetus’ CO2, nitrogenous wastes, etc

Front 11

Bilaminar Disc

Back 11

Inner cell mass forms 2 layers spontaneously during STB's activities: epiblast (columnar) and hypoblast (cuboidal) -> known as Bilaminar Disc

Front 12

Peculiarities of Human Implantation (3)

Back 12

-Hemochorial Placenta-free surface of pre-embryo (chorion) bathed directly in maternal blood
-Human implantation is Interstitial- pre-embryo completely surround by maternal tissue
-Necessary or maternal blood will leak into lumen of reproductive tract (uterine cavity)

Front 13

Abnormal Implantation, Ectopic Implantation, and most common type of abnormal implantation

Back 13

-An Abnormal Implantation is one that occurs in any site other than the upper, posterior portion of the uterine body.
-An Ectopic Implantation (pregnancy) is any abnormal implantation where development occurs outside of the uterine lumen.
-About 95% of all abnormal implantations are ectopic implantations but the two are not synonymous
-Placenta Previa is the most common type of abnormal implantation

Front 14

Placenta Previa and Solution

Back 14

-Placenta forms across “internal os” of cervix. -During normal birth, first baby, then placenta exits so that while in transit, baby is still breathing via placenta. With placenta previa, placenta can detach as birth occurs, and the fetus will suffocate.
-Solution = Caesarian Section

Front 15

Ectopic Pregnancy - most common

Back 15

-Defined as an Implantation where development of conceptus occurs outside uterine lumen
-About 95% of ectopic pregnancies occur in the Uterine Tubes, but tubal pregnancy and ectopic pregnancy not synonymous
-Rest of ectopics occur at scattered sites, e.g., mesentery, rectouterine pouch, ovary, etc.

Front 16

Predisposing Factors to Ectopic Pregnancy (3)

Back 16

-Prior pelvic surgery (e.g. appendicitis) -> may have compromised functional tubes
-Past history of use of IUD (Intrauterine birth control device, which prevents implantation of an embryo into the uterus should fertilization occur.)
-Pelvic inflammatory disease (PID): explains why ectopic pregnancies are more prevalent in urban populations, e.g., Chlamydia trachomatis infections, syphilis, gonorrhea

Front 17

Signs and Symptoms of Rupture (3)

Back 17

-Reproductively competent, sexually active, sudden onset of unilateral lower quadrant pain
-Distended firm abdomen with rebound tenderness -> indicates bleeding out into abdomen
-Normal temp, tachycardia (fast heart rate), decreased BP, decreased hematocrit, positive beta-hCG

Front 18

Treatment

Back 18

-Early Ultrasound when pregnant establishes implantation site and can rule out or diagnose ectopic pregnancy
-If unruptured, then use of Methotrexate (antimetabolite drug that inhibits DNA synthesis, then need to remove compromised tube) or surgical removal and repair
-If ruptured, then Surgical Removal and repair