Exam 2: Lecture 20: Development of the Female and Male Systems Flashcards
What is an embryo?
-Organism in early stages of development
-Generally has not acquired an anatomical form readily recognizable in appearance as a member of a specific species
-Placentation has not yet taken place
What is a fetus?
-Potential offspring within the uterus that is generally recognizable as a member of a given species on U/S
-Marked by development of placenta
What is embryology?
-Primary embryonic germ layers
The embryo starts as what that eventually turns into what?
-Starts as mass of cells that eventually form cell layers & will differentiate into embryo proper & placenta
What does the endoderm become?
-Digestive system
-Lungs
-Endocrine system
What does the mesoderm become?
-Muscle
-Skeleton
-Cardiovascular
-Reproductive system
What does the ectoderm become?
-Nervous system
-Skin
-Hair
What eventually makes the yok sac in embryology and placentation?
Blastocel
What is the posterior lobe of the pituitary gland, what does it contain, and what is the other name?
-Neural tissue
-Contains axons & nerve terminals of neurons from hypothalamus
-Neurohypophysis
What is the anterior lobe of the pituitary gland, where is it from, and what is the other name?
-Stomodeal ectoderm (tissue from roof of mouth, glandular epithelial cells produce glycoprotein hormones)
-Adenohypophysis
The posterior lobe of the pituitary is formed from
-A diverticulum from the floor of the brain called infundibulum
The anterior lobe of the pituitary is formed from
-An evagination from the oral cavity called Rathke’s Pouch
The pituitary gland lives in a bony prominence called the
-Sella turcica
What are the major hormones produced by the posterior pituitary?
-Growth hormone
-Prolactin
What are the major hormones produced by the anterior pituitary?
-ACTH
-TSH
-FSH
-LH
What are 3 things produced by the posterior pituitary and where are they?
-ADH -> kidney tubules
-Oxytocin -> smooth m. in uterus, mammary glands
What 5 things are produced by the anterior pituitary and where are they?
-Gonadotropins -> ovaries & testes
-Growth Hormone -> bones, tissues
-Prolactin -> mammary glands
-ACTH -> adrenal cortex
-TSH -> thyroid gland
How are hormones released in the posterior pituitary?
-Neurohormones are deposited directly into circulation
How are hormones released in the anterior pituitary?
-Utilizing hypothalao-hypophyseal portal system
Sexual differentiation involves
Specific substances
What is the definition of “sex differentiation”?
-Process where a group of unspecified cells develops into a functional, recognizable group of cells
-Ex: male & female reproductive tracts
What is the definition of “sex determination”?
-System that determines the sexual characteristics of an organism which generally consists of genetic or hormonal parameters
What is the definition of “karyotype”?
-Describes chromosomal complement of an organism
What is a genotype?
-Describes alleles genetic constitution of an individual (deals with/ genes or alleles that code for specific traits)
-Mendel’s Square
What is a phenotype?
-Describes observed characteristics (ex: penis, vulva, testicles)
What is a chimera?
-Produced by fusion of 2 different zygotes in a single embryo
What is a mosaic?
-Individual w/ 2 different cell lines that originated from same individual
What is this an example of?
-Chimera
-Cells contain 2 types of DNA (2 embryos fused together)
Most male tortiseshell cats are
-Chimeras
This is an example of
-Mosaic
-Individual has 2 or more genetically different sets of cells in their body
Downs syndrome is a example of
-Mosaic
Sexual differentiation relies on 3 stages, what are they?
- Chromosomal sex (karyotype)
- Gonadal Sex
- Phenotypic sex
each stage is dependent on the previous stage
How is chromosomal sex determined?
-At fertilization
How is gonadal sex determined?
-By the “sex determining region of the Y chromosome” (SRYgene)
-Srygene induces testes formation
How is phenotypic sex determined?
-By substances produced in the male testes to cause regression of female tract & formation of male tract
The karyotype of the organism involves the number of chromosomes followed by ____, which only tells the observer what?
-XX for female
-XY for male
-Only tells if chromosomally female or male
The embryo starts in a sexually ____ stage
indifferent
The cloaca will become
the anus
____ migrate from yok sac up into the gonadal ridge & will differentiate from there
Primordial germ cells
Pronephros become
-Primitive kidney (1st of 3)
Mesonephros become
-Intermediate kidney (2nd of 3)
-Male: form efferent ducts
-Female: regress
Metanephros become
-Final functional kidney (3rd of 3)
-Functional kidney
Mesonephric ducts (wolffish ducts) become
-Male: epididymis & ductus deferens
-Female: regress
Paramesonephric ducts (Mullerian ducts) become
-(Located beside mesonephric ducts)
-Male: regress
-Female: Uterus & oviducts & cranial vagina
Primitive sex cords become
-Male: seminiferous tubules
-Female: regress, primitive follicular cells
Primitive germ cells become
-Male: spermatogonia
-Female: oocytes
Determination of physical sex organ characteristics relies on the presence of
-Initially, hormone Testis Determining Factor (TDF) & “sex-determining region Y” (SRY)
-Then, Anti-Mullerian Hormone (AMH) causes degeneration of paramesonephric duct
-Last, Dihydrotestosterone (DHT) causes development of penis, scrotum, & accessory sex glands
What happens with a female XX chromosomal pair?
No SRY protein -> ovaries develop -> no AMH -> paramesonephric ducts become oviducts, uterus, cervix & part of vagina -> complete female tract
What are the steps in the developmental sequence of the testis?
- Undifferentiated sex cords align themselves
- Rete tubules & mesonephric tubules now interconnected & become seminiferous tubules
- Mesonephric duct transformed into epididymis & ductus deferens
AMH (anti-mullerian hormone) is produced by
Sertoli cells
Presence of testosterone causes
regression of the female duct system
How do the testes descend?
-Prior to descent, testes in retroperitoneal position
-Gubernaculum connects fetal testis to peritoneum
-After gubernaculum goes through inguinal ring, there is rapid growth of distal gubernaculum
-Testes pulled through inguinal canal by gubernaculum shrinking & abdominal pressure from visceral growth provides extra push for testes
-Continually shrinking gubernaculum keeps pulling testis into scrotum & testis now surrounded by double layer of peritoneum in scortum
The remnants of the gubernaculum become
-Proper ligament of the testis & the ligament of the tail of the epididymis
Male differentiation begins with
Sexually indifferent stage
What happens in the presence of AMH in male differentiation?
-Paramesonephric/Mullarian ducts regress
-Gonads increase in size (cause Mullarian ducts to disappear)
-Kidneys (metanephros) grow & move cranial
The remnant mesonephros are the
future efferent ducts
In female differentiation, the absence of testosterone, AMH & DHT causes
-Coelomic epithelium to become the ovarian cortex
-Rete tubules have disappeared
-Paramesonephric (Mullarian) duct develops & enlarges
-Mesonephric ducts regress completely
-Follicles begin to develop
In female differentiation, what forms the cervix & uterine body?
-Paramesonephric/Mullarian ducts fusing
In female differentiation, the caudal vagina originates from
-The urogenital sinus that invaginates from the exterior skin, so is stratified squamous epithelium
What forms the cranial vagina?
-The paramesonephric ducts completely fuse more caudally & form the body of the uterus, the cervix, or the cranial vagina
What forms the broad ligament that supports the reproductive tract in the abdominal cavity
-The connective tissue layer from the peritoneum
In external differentiation, the cloacal folds turn into
A scrotum & penis or labia
What happens to the cloacal folds when there is DHT?
-Genital swelling -> scrotum & urethral groove
What happens to the cloacal folds when there is no DHT?
-No genital swelling -> major & minor labia of vulva, vulvar cleft, clitoris
The fetal stage consists of
Rapid fetal growth & maturation of the organs that were produced during embryonic stage
What happens in fetal maturation in the male?
-Testicles descend into scrotum
What happens in fetal maturation in the female?
-Broad ligament develops
-Ovaries migrate caudally due to fetal growth
