Lecture 10: male reproductive Flashcards
Where does reproductive tissue originate from
the mesoderm
what seeds the reproductive tissue
germ cells which originate from the yolk sac
-future gonads (allows for future SPERMATOGONIA or OOGONIA)
What is sex determination based on
presence of the Y chromosome
-male Y chromosome is ~ 30% smaller
What are the 4 parts of the male reproductive system
- Gonads (testes, site of spermatogenesis)
- Genital ducts (transport, storage)
- Accessory glands (secretions)
- Penis (External support structure)
structure of Testes
- paired
- 2.5cm diameter and 4cm long
- 2 tunics
what are the 2 tunics of the testes
- Tunica Vaginalis
- derived from peritoneum
- external - Tunica Albuginea
- fibrous capsule
- internal
What are the lobules of the testes
- testes contain 200-300 lobules
- each lobule has 1 - 4 coiled seminiferous tubules
- in their wall holds SPERMATOGONIA
- stem cells (names change with stage of development)
What is the seminiferous tubules
- located within the testes
- specific site of meiosis allowing for the creation of SPERMATOZOA
- leads into the epididymis
What are the Interstitial Endocrine Cells (LEYDIG) and their function
- found in the c.t. surrounding seminiferous tubules
- produce androgens (the most abundant and effective being testosterone, small amounts of estrogen)
What are the Steroli Cells and their function
- aka sustentacular cell “nurse”
- btw spermatogonia (stem cells)
- forms the blood-testis barrier (attached to each other by tight junctions, form 2 compartments, protects developing sperm from immune system)
- secretin inhibin (can inhibit GnRH & FSH, negative feedback in sperm production)
- secrete androgen-binding protein (makes testosterone more water soluble, increases testosterone concentration in seminiferous tubules)
How many spermatozoa are produced daily approx)
400 million
what are the 3 structural divisions of spermatozoa
- genetic division (head)
- Metabolic division (midpiece)
- Locomotor division (Tail))
how long does spermatogenesis take approx.
24 days
what is the name of the specialized tip of the sperm head
Acrosome
-it is a specialized type of lysosome that contains hydrolytic enzymes (hyaluronidase) that permit the penetration of the head into the ovum
what is in the head of the spermatozoa
contains the nucleus with genetic material = DNA
what is the process called CAPACITATION
when mature spermatozoa must remain in female reproductive system for 10hrs before being able to fertilize the ovocyte
- during this period the membrane of the acrosome is thinned so that it is easier to release its enzyme
how long do spermatozoa live in the female reproductive system
~ 48 hrs
when is the capacity to fertilize at its maximum
btw 24 and 72 hrs
how many sperm are required for fertilization
only 1
-but need multiple to break down membrane of ovum
What is in the midpiece of the spermotozoa
- contains mitochondria that supplies energy necessary for its propulsion (movement)
- mitochondria are lined up in the midpiece
- only the mothers mitochondria are transferred (paternal mitochondria are separated from the gentic info)
what is the function of the Tail of the spermatozoa
- aka Flagellum (formed from microtubules)
- that serve for propulsion (propeller)
What hormonal regulation is promoted by spermatogenesis
the production of testicular androgens
Androgen hormones are ANABOLIC and allow for
- stimulate synthesis of proteins
- allows for sexual dimorphism (e.g. male-female difference in body size and muscle mass)
What controls the homeostasis and regulation of androgen release
Brain-testicular axis
- hypothalamus
- Adenohypophysis (anterior pituitary)
- testes
-each component of the brain-testicular axis is controlled by the CNS
What is GnRH
Gonadotropin-releasing hormone
how does GnRH arrive at the adenohypophysis
by hypophyseal portal system
- binds to pituitary (hypophyseal) cells
- leads to release of gonadotrophins of the anterior pituitary (adenohypophysis)
what is FSH and function
Follicle stimulating hormone
-development of seminiferous tubules and spermatogenesis
what is LH and its function
Luteinizing hormone
-stimulates interstitial cells to secrete testosterone (also a bit of estrogen which is essential for normal development of bone)
What are the testicular hormones that bring about inhibition of cells
- testosterone & inhibin
- Sertoli (sustentacular) cells secrete INHIBIN when spermatogenesis is sufficient (secrete less when spermatogenesis is insufficient)
What is the Testosterone negative feedback mechanism
- Elevated levels of testosterones
- inhibits secretion of GnRH
- Reduction in the release FSH & LH
- Reduces testosterone production
What is the basis of LIBIDO (sex drive)
Testosterone
- for both sexes
- females secrete via adrenal glands
What is testosterone synthesized from
Cholesterol
-to be able to do it’s action, it must be converted to DHT (dihydrotestosterone) in certain target cells (e.g. testes, prostate, hair follicles, adrenal glands)
what is the flow of spermtozoa
- coiled semiferous tubules
- tubules rectus (or straight tubules)
- Rete testis
-fluid movement is controlled by testicular fluid pressure
Structure and function of Epididymis
- spermatozoa stay ~ 20 days
- 4-6 meters long
- if present many months they degenerate
- increase surface of reabsorbtion of degenerated spermatozoa (phagocytosis)
- reabsorb testicular fluid if in excess
- feed spermatozoa
What is Ductus (Vas) Deferens
- ends at the Ampulla
- it is about 45cm long (passes on the side of the urinary bladder, can take many months)
- movement is controlled by PERISTALSIS
Structure of the wall of ductus vas deferens and its function
- pseudostratified columnar epithelium & 3 layers of smooth muscles
- function: gamete storage
What is a vasectomy
sectioning & ligature of ducts deferens
Structure of the ejaculatory duct
- ~ 2cm long
- Formed by the union of 2 structures:
1. AMPULLA of the ductus deferens
2. Excretory duct of the seminal vesicle - movement is maintained by peristaltic contraction
Structure of the urethra
- Prostatic urethra ~ 23cm in length
- Membranous urethra ~ 1cm
- Spongy / Penile urethra ~ 15cm
Penis function
- organ of copulation
- delivery of sperm to female reproductive system
- contains: body (shaft) & root
Penis structure
- made of 3 cylindrical bodies composed or erectile tissue (c.t & smooth muscle tissue riddled with vascular spaces)
- there are 2 dorso-lateral bodies named Corpus (corpora) cavernosa
- there is 1 medioventral body, smaller, called Corpus Spongiosum
- Glans Penis = enlarged end of penis (skin covering called Prepuce = foreskin)
What is circumcision
the removal of the prepuce via surgery
What is location of the scrotum
exterior to the abdomino-pelvic cavity
what is the structure scrotum
- sac of skin containing the testes (divided in 2)
- the wall contains the Dartos (smooth muscle responsible for wrinkled appearance)
What is the cremaster reflex
movement of scrotum away or closer to body for heat regulation
-Dartos and Cremaster (skeletal) adjusts height of testes
Where does autonomic nervous system in scrotum receive it’s input from
from FSH of the endocrine system
What do sympathetic and parasympathetic nervous system help with (scrotum)
- regulate testes temperature
- Irrigation: from abdominal aorta to testicular artery (testicular veins form the Pampiniform Plexus branches around the artery, it absorbs heat frm artery cooling it before it enters testes)
What temp maximizes production of spermatozoa
when testes are 3 decrees C lower than the body
What are the 3 different accessory gland types that emit secretions into the semen
- Seminal Vessicles (paired)
- Prostate (unpaired)
- Bulbourethral Gland (paired)
What is structure and location of seminal vesicles
-convoluted pouches 5 to 7 cm long on posterior surface of bladder
What is function of seminal vesicles
secrete the viscous, alkaline, nutrient-rich part of seminal fluid (60% of semen volume)
What is structure and location of prostate gland
- Doughnut shaped
- Encircles urethra just below bladder
What is function of prostate gland
adds slightly acidic, watery, milky-looking secretion to seminal fluid (30% of semen volume)
What is structure and location of Bulbourethral glands (glands of Cowper)
- small pea-shaped structures with approx. 2.5cm long (1 inch) ducts leading into urethra
- lie below prostate gland
What is the function of Bulbourethral glands
-secrete fluid that is part of semen (5% of semen volume) during erotic stimulation
What is appearance (origin of this appearance) of Semen
- Whitish liquid (frm prostate)
- Slightly Sticky / Viscous (frm seminal vesicles & bulbourethral glands)
What does semen contain
spermatozoa (50 - 130 million/ml)
secretions of all the accessory glands
What is the pH of semen
7.2 - 7.6
How much semen is secreted in ejaculation
~25ml
