GU Phys 2 Flashcards
Spermatogenesis
- define
- where does it occur
- male gamete formation via meiosis
- occurs in seminiferous tubules
Spermatogenesis
- what stimulates it
- when does it start
- how much per day
- testosterone
- starts at puberty (~14 yo)
- continues through life
- produce 100m sperm daily
Meiosis I and II
review :)
Spermatogonia
- location
- what type of cell
- action
- outermost cells of seminiferous tubules near basal lamina
- stem cell
- divide by mitosis to produce clonal diploid cells
Spermatogonia divide into what two types of cells
A: remain at basal lamina as spermatogonium (pluripotent)
B: move toward lumen, differentiate into primary spermatocyte
Spermatogenesis Meiosis
- primary vs. secondary spermatocyte
- Primary: undergo meiosis I to produce secondary spermatocytes
- Secondary: undergo meiosis II to form spermatids
Spermatids
- describe
- location
- immature sperm
- round, small cells, large nuclei
- near the lumen
When do sperm become motile?
when they exit the body
Spermiogenesis
- describe process
- process by which spermatids mature into sperm (not yet motile or fertile)
- Golgi packages acrosomal enzymes, positioned anterior to nucleus
- cytosol sloughs off to streamline the cell
- multiplication of mitochondria, position proximal to the tail
- microtubules form flagellum
Sertoli Cells
- location
- role
- surround developing sperm
- deliver nutrients
- tight junctions open and close as spermatocytes move toward lumen
- secrete testicular fluid
- dispose of sloughed cytosol
- produce ABP
What is ABP
- Androgen binding protein
- androgen is testosterone
- allows testosterone to be held in close proximity to spermatogenesis
Capacitation
- describe
- final phase of maturation
- produces motile, fertile sperm
- occurs post ejaculation
How does the female body effect capacitation
sterol binding proteins, enzymes
FPP
Fertility promoting peptide
- part of capacitation
- secreted by prostate
- increases cAMP in sperm cell, Ca2+
- leads to motility
Acrosomal reaction in capacitation
- destabilizes the acrosome
- acrosomal enzymes degrade the bona pellucid coat of ovum
What are the four main parts of the penis
- root
- shaft
- glans
- foreskin
What are the three columns of erectile tissue
- connective tissue
- smooth muscle
- vascular spaces
Corpus spongiosum
- location/anatomy
- muscle
- midline, surrounds urethra
- expands distally to form the glans
- secured to the urogenital diaphragm
- proximally forms root covered by bulbospongiosus muscle
Corpus cavernosa
- location/anatomy
- muscle
- two paired bodies
- proximal end form crura
- anchors to the pelvic arch
- each crux surrounded by ishiocavernosus muscle
Unstimulated penis
- state of blood vessels
arterioles supplying erectile tissue (cavernous) are constricted
Stimulated penis
- state of blood vessels
- vasodilation causes engorgement
- erectile reflex
Erection reflex
- initiated by what
- physical receptors on skin of glans
- emotional, visual, mental activity
- 2nd-4th sacral segments of spinal cord
CNS response in erection reflex
- PNS
- sensory/somatic fibers
- parasympathetic nerves of pelvic splanchnic to nerves serving penis
- sensory and somatic fibers of pudendal nerve serve skin and muscle, including pelvic sphincters and pelvic floor
What is effect of parasympathetic input in the erection reflex
- causes vasodilation of internal pudendal arteries (engorgement and expansion)
- pressure from 35-100 mmHg
- compression of veins prevents outflow
What is contained in the parasympathetic fibers of the pelvic plexus
NOS
nitric oxide synthase
What does the release of NO do?
- inhibits phosphodiesterase (PDE) breakdown of cGMP which is necessary for vasodilation
- NO is a PDE inhibitor
- creates and prolongs erection
(also the ED drugs)
What happens when stimulus ends or ejaculation occurs?
- sympathetic tone reduces blood flow and blood pressure
- venous flow increases
- detumescence occurs
Ejaculation
- neural input from where
- SNS from T10-L2
- to lumbar splanchnic nerves
- strong and rhythmic contraction
Ejaculation
- result of neural input
- acts on smooth muscle along entire tract
- leads to contraction of ducts and glands
- propels sperm forward to urethra
- contraction of pelvic floor helps propel semen to exterior
Ejaculation
- what prevents urine back flow?
- urinary sphincter
What are the systemic effects of SNS input during ejactulation
- pleasure
- elevated HR, BP, Resp Rate
The brain-testicular axis:
- GnRH
- source
- target
- action
- inhibited by what
- Gonadotropin releasing hormone
- produced and released by hypothalamus
- anterior pituitary
- prompts release of anterior pituitary gonadotropins (LH and FSH)
- inhibited by testosterone
Luteinizing Hormone
- source
- target
- action
- anterior pituitary
- targets gonads via circulation, receptor on interstitial cells of Leydig
- testosterone production
(under influence of GnRH)
Follicle stimulating hormone (FSH)
- source
- target
- anterior pituitary
Target: - gonads via circulation
- influences Sertoli cells to secrete ABP (androgen binding protein)
- binds testosterone and DHT
- concentrates hormones within the luminal fluid of tubules (where needed for spermatogenesis)
FSH
- action
- stimulates spermatogenesis in seminiferous tubules
- stimulates sperm maturation in the epididymis
Testosterone
- source
- synth from cholesterol in interstitial cells
- also formed/secreted by adrenal cortex
Testosterone
- transport
protein bound for transport
- 65% to GBG (gonadal-steroid binding globulin)
- 30% to albumin
- 5% free
Testosterone
- elimination
- converted to ketosteroid and eliminated in urine
Testosterone
- action
- binds to intracellular receptor
- moves to nucleus
- affects transcription of multiple genes
Testosterone
- action
Testes
- enhances spermatogenesis
Systemic
- anabolic (protein synthesis, decreases degradation)
- increases/maintains bone and muscle mass
- sebum and hair production
- maintains adult size/fn of genital organs
- masculinization of brian (sexual behavior and territoriality)
Testosterone at puberty
- what causes increase in T?
- decreased inhibition of GnRH by hypothalamus
- increased GnRH results in increased testosterone release
- takes 3 years to reach adult levels
- results in masculinization of body (enlarged genitals, hair distribution, behavior)
Effects of testosterone at puberty
The list is VERY long, second to last slide
Inhibin
- where produced
- stimulated by what
- target
- action
- inhibited by what
- produced by Sertoli cells
- stimulated by FSH
- targets anterior pituitary
- inhibits release of FSH
- inhibited by GnRH
DHT (dihydrotestosterone)
- how made
- where located
- 5% of testosterone is converted to DHT by 5alpha-reductase
- predominant in scalp, prostate, genital tissue
DHT
- action
- binds T receptor, forming a more stable complex (kind of like super T)
- results in higher T activity
- male pattern baldness
- prostate growth
