Lecture 20: Dev of the Female & Male System (Exam 2)

Question 1

Define embryo

Answer 1

• An organism in the early stages of dev
• Has not an anatomical form that is readily recognizable in appearance as a member of a specific species

Question 2

T/F: Placentation takes place when there is an embryo

Answer 2

False; placentation has not take place

Question 3

Define fetus

Answer 3

• Potential offspring w/in the uterus that is gen recognizable as a member of a given species
• Marked by dev of placentation

Question 4

Define embryology

Answer 4

• Primary embroyonic germ layers
• Embryo starts as a mass of cells that eventually form cell layers & will differentiate into the embryo proper & placenta

Question 5

What do the endo, ecto, & Meso derm make

Answer 5

• Endoderm - digestive sys, lungs, & endocrine system
• Mesoderm - muscle, skeleton, cardiovascular, & reproductive sys
• Ectoderm - NS, skin, & hair

Question 6

What makes the yolk sac

Answer 6

The mesoderm

Question 7

Where do trophoblast come from

Answer 7

The embryo & the placenta

Question 8

Describe this pic

Answer 8

The hatched blastocyst consists of the inner cell mass (ICM), the trophoblast and the blastocoele. Very early in embryonic development, the primitive endoderm ( blue layer) begins to form beneath the inner cell mass and grows downward forming a lining on the inner surface of the trophoblast. At the same time the mesoderm ( red layer) begins to develop btw the primitive endoderm and the embryo
When the primitive endoderm completes its growth, it forms a cavity called a yolk sac. This cavity does not contain yolk but is so named because it is analogous to the yolk sac in avian embryos.
The mesoderm continues to grow, forming a sac and pushes against the trophectoderm ( previously the trophoblastic cells). The newly formed mesodermal sac pushes against the trophectoderm and begins to fold upward forming “ wing like” structures called amnionic folds
The mesoderm now completely surrounds the yolk sac and the developing allantois. The allantois is a diverticulum from the primitive gut that collects embryonic wastes. The mesoderm continues to fuse with the cells of the trophectoderm to form the chorion. The amnionic folds continue to ford upward around the embryo
The yolk sac begins to regress but the allantois continues to grow and expand. The amnionic folds almost completely surround the embryo. The leading edges of the amnionic folds will eventually fuse
The amnionic folds have completely fused resulting in the formation of a double sac around the embryo. The inner sac consists of trophectoderm and mesoderm and is called the amnion. It creates the amnionic cavity. The chorion completely surrounds the entire conceptus. The allantois continues to expand and begins to fill in the spaces of the cavity. Eventually the allantois and the chorion will fuse forming the allantochorion. The yolk sac continues to regress

Question 9

Where does urine & feces go from the baby

Answer 9

The allantois

Question 10

What are the two parts of the pituitary gland

Answer 10

Posterior & Anterior lobe

Question 11

Describe the posterior lobe

Answer 11

• Neural tissue
• Contains axons & nerve terminals of neurons from the hypothalamus
• “Neurohypophysis”

Question 12

Describe the anterior lobe

Answer 12

• Stomodeal ectoderm
• Tissue from the roof of the mouth & from glandular epithelial cells that make glycoproteins hormones
• “Adenohypophysis”

Question 13

What is formed from a diverticulum from the floor of the brain (infundibulum)

Answer 13

Posterior lobe

Question 14

What is formed from an evagination from the oral cavity known as Rathke’s pouch

Answer 14

Anterior lobe

Question 15

What happens to the stalk of the rathke’s pouch

Answer 15

It regresses & separates from the stomodeal ectoderm (roof of the mouth)

Question 16

Where does the pituitary lobe live

Answer 16

The turkish saddle

Question 17

What hormones come from each part of the pituitary gland

Answer 17

• Anterior: FSH, LH, GH, PRL, ACTH, & TSH
• Posterior: Oxytocin & ADH

Question 18

How do neurohormones make it to the neurohypophysis? What about the adenohypophysis?

Answer 18

• Neuro: They are deposited directly into circulation from the PVN
• Adeno: They utilize the hypothalmohypophyseal portal sys

Question 19

Define sex differentiation

Answer 19

The process whereby a group of unspecified cells develops into a functional, recognizable group of cells that have a common fxn

Question 20

Define sex determination

Answer 20

A system that determines the sexual characteristics of an organism which generally consists of genetic (alleles or genes) or hormonal parameters

Question 21

Define Karyotype

Answer 21

Describes the chromosomal complement of an organism

Question 22

Define genotype

Answer 22

Describes the alleles genetic constitution of an indiv meaning it deal w/ the genes or alleles that code for specific traits. Can determine the possible genes from two parents by using mendel’s square

Question 23

Define phenotype

Answer 23

• Describes the observed characteristics such as morphology, dev, blood types, behavior
• The expression of the characteristics depends on the genetics (genotype), but this is also affect by the envi

Question 24

Define chimera

Answer 24

Produced by the fusion of two different zygotes in a single embryo

Question 25

Define mosaic

Answer 25

An indiv w/ two different cell lines that originate from the same indiv

Question 26

What are the 3 stages of sexual differentiation

Answer 26

* Chromosomal sex - determined @ fertilization (X & Y determined by male sperm) * Gonadal sex - dep by the "sex determining region of the Y chromosome"; if its there and working right it will induce testes formation or not there/not working right * Phenotypic sex - determined by substances produced in the male testes to cause regression of female tract & form of a male tract EACH STAGE IS DEP ON THE PREV STAGE

Question 27

What stage does an embryo start in

Answer 27

Sexually indifferent stage

Question 28

Describe the sexually indifferent stage

Answer 28

* Primordial germ cells originate in the yolk sac * They then migrate through the hindgut to the undifferentiated gonad w/in the dorsal body wall (AKA the genital or gonadal ridge)

Question 29

Fill out the following chart

Answer 29

Question 30

What determines the physical sex organ characteristics & what do they do

Answer 30

* The hormone testis determining factor (TDF) & the sex determining region Y (SRY) on the Y chromosome causes development of the testes & starts the production of testosterone * The sertoli cells secrete anti-mullerian hormone (AMH) which causes degeneration of the paramesonephric duct * Dihydrotestosterone (Testosterone + 5alpha - reductase = DHT) causes dev of the penis, scrotum, & acc sex glands

Question 31

What is the default sex

Answer 31

Female (XX chromosomal pair)

Question 32

T/F: We can sex fetus once the gonads have dev beside the kidneys

Answer 32

True

Question 33

Describe the steps of the descent of the testes

Answer 33

1. The testes lie in the retroperitoneal position & the gubernaculum connects the fetal testis to the periotneum 2. The gubernaculum goes through the inguinal ring 3. There is a rapid growth of the distal of the gubernaculum 4. When the testes are in the inguinal region they are pulled through the inguinal canal due to the gubernaculum shrinking 5. Abdominal pressure from visceral growth provides an extra push for the testes 6. As the gubernaculum continues to shrink the testes are pulled into the scrotum 7. Once the testes are in the scrotum they are now surrounded by a double layer of peritoneum (visceral vaginal tunic & parietal tunic) w/ a vaginal cavity btw the two layers

Question 34

What do the remnants of the gubernaculum become

Answer 34

* Proper ligament of the testis * Ligament of the tail of the epididymis

Question 35

Describe the steps of male differentiation

Answer 35

1. Begin w/ sexually indifferent stage 2. Presence of AMH causes paramesonephric/mullarian ducts regress, gonads to increase in size, kidneys (metanephros) to grow & move cranially 3. Mullarian ducts almost completely regressed, gonads become larger, & kidneys become fully functional

Question 36

What happens if there is an absence of testosterone, AMH, & DHT

Answer 36

* Coelomic epithelium bill becomes the ovarian cortex * Rete tubules disappear * Paramesonephric (mullarian) duct develops & enlarges * Mesonephric ducts regress * Follicles beginning to develop * Distinct clusters of follicles @ periphery of ovary * The gonad resembles an ovary * Mesonephric ducts completely regress * Mullarian ducts fuse to form the cervix & uterine body * Small bud evaginates from the caudal urogenital sinus & attaches to the fused paramesonephric ducts * Caudal vagina originates from the urogenital sinus that invaginates from the exterior skin * Gonadal ridges & paramesonephric ducts become closely associated as they move ventrally * Repro tract get smushed btw/ 2 layers of peritoneum (genital fold) & forms the broad ligament that supports the repro tract in the abdomen

Question 37

Describe fetal stage

Answer 37

* Fetal stage consist of rapid fetal growth and maturation of the organs that were produced during the embryonic stage * In males - the testicles descend into the scrotum * In females - the broad lig dev & the ovaries migrate caudally due to fetal growth