Histology & Embryology Flashcards
Name the two roles of the ovaries
- produce gametes
- produce steroids
What are the two key structures in the ovary?
Medulla and cortex
Describe the ovarian medulla
Forms the core of the organ and contains loose connective tissue, contorted arteries, veins and lymphatics it is continuous with the hilum
Describe the ovarian cortex
Scattered ovarian follicles in a highly cellular connective tissue stroma - outer shell is a dense connective tissue layer (tunica albnginea covered by cuboidal epithelium- germinal epithelium)
What is the blood supply to the ovary?
Helicine arteries from the broad ligament
Name the five types of follicle
Primordial Primary Late primary Secondary Mature Graafian
How does a primordial follicle form?
Primary oocyte associates with pregranulosa cells which are squamous but change to cuboidal
Once the cells change from squamous to cuboidal what does the follicle become?
Primary follicle
Describe the primary follicle
A layer of extracellular matrix forms called the mona pellucida
Stroma cells are associating with the outside of the follicle and form the theca folliculi
Describe the late primary follicle
Granulosa cell layer proliferates, theca follicle forms the theca interna and secretes oestrogen precursors (converted to oestrogen by granulosa cells)
Theca externa is a fibroblast like outer layer
What structural changes occur to the secondary follicle?
Enlarges and the antrum forms, it fills with follicular fluid.
What is the cumulus oophorus?
Layer of cells surrounding the oocyte and keep it close to the follicular antrum
What happens to the graafian follicle?
One day before ovulation it will complete meiosis 1 and produce a secondary oocyte and polar body that carries the second nucleus away to degenerate
What is the name given to the granuloma cells surrounding the oocyte?
Corona radiata
What is the name of the structure left after the oocyte is released in ovulation?
Corpus luteum
What happens to the corpus luteum after ovulation?
No implantation - corpus albicans
Implantation - placenta secretes HCG to prevent degeneration of the corpus luteum to maintain progesterone levels
What cells line the ampulla of the uterine tubes?
Simple columnar epithelium with ciliated secretory cells
What cells line the isthmus of the uterine tubes?
Secretory epithelium
How many layers of muscle do the ampulla and isthmus have?
Ampulla - two layers
Isthmus - three layers
What are each of the layer of the uterus made of?
Endometrium - inner secretory mucosa
Myometrium - three layers of smooth muscle combined with collagen elastic tissue
Perimetrium - loose connective tissue covered by mesothelium
What are the two layers of the endometrium?
Stratum functionalis
Stratum basalis
What is the cellular transition of the cervix?
Stratified squamous epithelium transitions to simple columnar epithelium
Name the four layers of the vagina
- Non-keratinised stratified squamous epithelium
- Lamina propria
- Fibromuscular layer (inner circular and outer longitudinal smooth muscle)
- Adventitia
What immune barrier is present in the vagina?
Commensal bacteria metabolise the glycogen to lactic acid which inhibits growth of pathogenic bacteria
Describe the mons pubis
Skin which contains highly oblique hair follicles overlying subcutaneous fat pad which overlies pubic symphysis
What is the labia majora?
Continuation of the mons pubis - apocrine sweat glands and sebaceous glands with bundles fo smooth muscle
What is the labia minora?
Thin skin folds - no fat or hair follicles rich in vasculature and sebaceous glands
Describe the cellular transition at the hymen
Keratinised epithelium becomes non-keratinised stratified squamous epithelium
Describe the clitoris
Two tubes of erectile vascular tissue covered by fibro-collagenous sheath - rich innervation and thin epidermis
What gestational day does the embryo attach to the uterine wall?
Day 6
Name the two layers the embryo forms
Epiblast and Hypoblast
Describe grastrulation
Cells from the epiblast migrate towards and through the primitive streak to form a new layer (mesoderm)
What do the epiblast and hypoblast become?
Ectoderm and Endoderm
Name the three parts of the mesoderm
Paraxial
Intermediate
Lateral
What processes allow formation of internal organs?
Folding - lateral and cranial/caudal
Which layer does the urogenital system arise from?
Intermediate mesoderm
What are the names of the longitudinal masses formed on either side of the primitive aorta?
Urogenital ridges
Name the structure where the excretory ducts enter
Cloaca
At what week does gonad differentiation start to occur
Week 7
Which cells ultimately make sperm and ova?
Primordial Germ Cells
What do the genital ridges eventually form and what from?
Gonads
Coelomic epithelium - mesothelium lining of the peritoneal cavity
What happens as the primordial germ cells are enveloped in the genital ridge?
Formation of sex cords
Name the two genital ducts
Mesonephric (male)
Paramesonephric (female)
Where do the genital ducts connect?
Into the posterior wall of the urogenital sinus
What signals for female development?
Absence of SRY transcription factor
What is another name for cortical cords?
Secondary sex cords - incorporate germ cells into them
What happens to the germ cells in the sex cords in female development?
Differentiate into oogonia and primary oocyte and rest in prophase 1
What is the significance of theca cells?
Produce androgens required to stimulate oestrogen production which in turn stimulates development of paramesonephric ducts
What do the paramesonephric ducts become?
Uterine tubes, uterus, superior vagina
Name the three parts of the paramesonephric ducts
- cranial portion opens up to coelomic cavity
- horizontal portion crosses the mesonephric duct
- caudal portion fuses with the paramesonephric duct not he other side
Describe the uterovaginal canal
Fusion of caudal portion, gives rise to the uterus and superior vagina
What does the urogenital sinus become?
Sinuvaginal bulb then by vacuolisation forms a lumen
What signals for male development?
SRY transcription factor
What cell does SRY transcription factor stimulate?
Sertoli cells
What happens to the cells that do not become sertoli cells?
Engulfed in seminephrous tubules
Name the sperm precursor
Spermatogonia
When the testis cord anastomose what is formed?
Rete testis - connects the mesonephric duct which will ultimately be the Vas deferens
What is the function of AMH?
Degeneration of paramesonephric duct
What do sertoli cells stimulate?
Gonadal ridge cells to form leydig cells
What is the function of leydig cells?
Secrete testosterone
Name the structures that testosterone induces the formation of
Epididymis, vas deferens, seminal vesicles
What hormone induces male specific external genitalia?
Dihydrotestosterone (DHT)
Where do the testes originate?
10th thoracic level
What structure pulls the testes caudally?
Gubernaculum
Name the three male accessory glands
- prostate
- bulbourethral
- seminal
