Flashcards in Unit 7 - Male Reproductive System Deck (64):
where are the testes located? when do they descend?
within scrotum, suspended by spermatic cords
-scrotum maintains testes at temperature 2 degrees below abdominal temp (for sperm production)
-testes descend from abdomen into scrotum via inguinal canal at 26 weeks gestation
serous sac of simple squamous epithelium consisting of outer parietal and inner visceral layers
-visceral layer adheres to tunica albuginea on anterolateral surface of each testes
-extension of abdominal peritoneum that was carried along during descent
where do testes receive blood? get blood taken away?
testicular artery - highly convoluted near testis
pampiniform venous plexus - surrounds testicular artery and carries blood away from each testis
thick capsule of dense irregular connective tissue covering each testis
what are the 2 genital ducts?
intratesticular ducts and excretory ducts
thickening of tunica albuginea on posterior surface
-vessels and ducts pass thru it as they enter/leave testes (no tunica vaginalis)
-projects inward giving rise to incomplete septa that divide each testis into 250 lobules
~250 per testis with 2 major components
-1-4 seminiferous tubules per lobule
-loose connective tissue stroma (interstitial tissue) with blood vessels, lymphatics, nerves, and Leydig cells
where spermatozoa are produced via spermatogenesis and aided by Leydig cells
-lined with stratified germinal epithelium
-each forms a convoluted U-shaped loop beginning and ending near mediastinum
-surrounded by tunica propria with myoid cells and fibroblasts
straight tubules; short tubules within mediastinum that connect seminiferous tubules with rete testis
-lined with epithelium consisting of only Sertoli or simple cuboidal cells
-supported by a dense CT sheath (no spermatogenic cells present)
anastomotic network of channels in mediastinum that connect tubuli recti to ductuli efferentes
-lined with simple epithelium that varies from squamous to low columnar
-produces testicular fluid for sperm transport (also made by Sertoli)
efferent ductules; 10-20 ducts that connect rete testis to epididymis
-lined with simple epithelium that appears scalloped due to alternating groups of cells:
--non-ciliated cuboidal (low columnar) cells with microvilli on apical surface
---absorb most of the testicular fluid made in seminiferous tubules
--ciliated tall columnar cells
---contain the only true cilia in male reproductive system
---cilia beat in direction of epididymis sweeping spermatozoa along in that direction
what are myoid cells?
cells in tunica propria of seminiferous tubules that have contractile properties that help move spermatozoa and testicular fluid through seminiferous tubules
fibrous peritubular tissue that surrounds seminiferous tubules
-has layers of fibroblasts and myoid cells
what are the steps of spermatogenesis?
formation of haploid spermatozoa (spermatozoids or sperm) from undifferentiated diploid germ cell (spermatogonium)
-occurs in inward direction from basal lamina towards lumen
-takes 64 days
-needs testosterone from Leydig cells in interstitial tissue (normal adult makes >100 million sperm/day)
what are spermatogonia? difference between type A and B?
diploid (2N DNA) and begin dividing by mitosis at puberty
-A: continue dividing as stem cells
-B: progenitor cells that differentiate into primary spermatocytes
--increase number through mitosis
--daughter cells remain attached to each other by cytoplasmic bridges; allow coordination of spermatogenesis events between cells b/c of communication via bridges
what do spermatogonia look like histologically?
round cells sitting on basal lamina
-heterochromatic (dark) nuclei
what are primary spermatocytes?
diploid (4N DNA)
-made by mitotic division of spermatogonia B followed by DNA replication
-enter prophase I after formation (takes 22 days)
-genetic material is exchanged between paired homologous Xm (recombination) to generate genetic diversity (reduction division)
-each creates 4 haploid gametes
what do primary spermatocytes look like histologically?
largest germ cells
-large nuclei containing thick strands of condensed chromatin
what are secondary spermatocytes
haploid (2N) made by meiosis (reduction division)
-short lived so hard to find in sections
-immediately enter prophase without making new DNA (NO S PHASE)
-undergo meiosis II to create 2 spermatids
what are spermatids?
haploid (1N DNA)
-differentiate into spermatozoa via spermiogenesis
what do spermatids look like histologically?
small cells that are numerous near lumen of seminiferous tubule
-early spermatids have small condensed nuclei
-late spermatids have tiny, highly condensed nuclei
what is spermiogenesis?
the final step of spermatogenesis converting spermatids into spermatozoa
-involves no cell division
-occurs while spermatids are bound to Sertoli cell membrane
what are 5 changes that happen during spermiogenesis?
1. acrosome formation
2. flagellum formation
3. nuclear changes
4. change in orientation
5. later changes (spermiation)
what happens in acrosome formation?
granules accumulate in Golgi and coalesce into a large acrosomal vesicle adjacent to nuclear envelope
-vesicle spreads over anterior half of condensing nucleus forming acrosomal cap (acrosome) which has hydrolytic enzymes that dissociate cells of corona radiata and digest zona pellucida of oocyte
what happens in flagellum formation?
centrioles migrate from next to nucleus to a position near cell surface opposite the forming acrosome
-one centriole initiates assembly of microtubues, forming flagellum
-mitochondria aggregate around proximal part of flagellum forming middle piece where swimming movement is generated
what are nuclear changes that occur in spermiogenesis?
nucleus condenses, elongates, and moves anteriorly, displacing cytoplasm posteriorly
how is the orientation changes in spermiogenesis?
halfway through, the spermatid reorients itself so the head points toward the basal lamina, and developing flagellum extends into lumen
what is spermiation?
excess cytoplasm (residual body) is released and phagocytosed by Sertoli cells
-spermatids are released from Sertoli cells and from each other into lumen as spermatozoa
what is the structure of the spermatozoa?
head - flattened and pointed; consists of highly condensed nucleus with anterior 2/3 covered by acrosomal cap containing enzymes required for penetration of ZP of oocyte
midpiece - contains mitochondria wrapped around flagellar axoneme
tail - has fibrous sheath wrapped around flagellar axoneme
what are histological features of Sertoli (sustentacular) cells?
tall columnar non-replicatng epithelial cells
-adhere to basal lamina and extend to lumen of tubule
-apical and lateral processes envelop spermatogenic cells
-euchromatic nucleus is ovoid or triangular with deep infoldings and a prominent nucleolus; shape and location of nucleus varies
-connected tightly to neighboring Sertoli cells via occluding junctions at basolateral part of cell
-junctions establish basal and luminal epithelial compartments
-spermatogonia and early primary spermatocytes are restricted to basal compartment while more mature spermatocytes and spermatids are restricted to luminal compartment
what are Sertoli cell functions
1. support, protect, and provide nutrition to developing spermatozoa isolated from blood supply by blood-testis barrier (mediate exchange of nutrients and metabolites)
2. phagocytosis of residual bodies shed from spermatids and degenerating spermatogenic cells that failed to differentiate properly
3. secretion of testicular fluid of tubule for sperm transport; also secretion of androgen binding protein (to concentrate testosterone in seminiferous tubule) and hormones that regulate release of FSH in anterior pituitary
4. blood-testis barrier created by tight junctions between Sertoli cells
-protects sperm from blood-borne toxic agents and isolates antigenic germ cells from male immune system
why do sperm-specific Ab in semen cause infertility?
may cause sperm to agglutinate to impair movement
what is interstitial and the components?
tissue between seminiferous tubules
-consists of nerves, blood vessels, lymphatics, and connective tissue
--CT includes Leydig cells, fibroblasts, macrophages, and mast cells
what do Leydig cells do?
steroid secreting cells that are apparent during puberty
-produce >95% of testosterone
-active for 4 mo in male fetuses then quiescent until puberty
what do Leydig cells look like histologically?
large rounded or polygonal cells with central nuclei
-eosinophilic cytoplasm due to extensive SER (rich in lipid droplets)
--cytoplasm may have yellow-gold lipofuscin that increases with age
factors affecting spermatogenesis
-general or local infections
-systemic diseases (fever, kidney disease, metabolic disorders)
-steroid hormones and related mediccations (decreased FSH secretion)
-toxic chemicals (pesticides, plastics, PCBs)
-elevated testicular temperature (hot tubs)
what is cryptorchidism?
failure of descent of one/both testes
-occurs in 3% of full term and 33% of premature newborns
-untreated men are sterile with increased risk of testicular cancer
-no effect on development of secondary sexual characteristics
what cells are less vulnerable to dietary deficiencies and mutagenic agents than the dividing and differentiating germ cells?
non-dividing Sertoli and Leydig cells, and reserve stem cells
what do excretory ducts do?
carry spermatozoa from scrotum to penile urethra during ejaculation and include ductus epididymis, ductus deferens, and urethra
what do intratesticular ducts do?
carry spermatozoa and fluid from seminiferous tubules to epididymis
crescent shaped structure on superior and posterior surfaces of testis
-divided into head, body, and tail
-spermatozoa enter at the head on superior surface of testis
-consists of single highly coiled tube (ductus epididymis) and associated smooth muscle cells and loose CT
structure of epididymis
1. ductus epididymis - highly coiled tube lined with pseudostratified columnar epithelium
-basal cells - rounded stem cells on basal lamina
-principal cells - tall columnar cells with sterocilia and basally located nuclei
2. smooth muscle cells surround ductus epididymis
-thin circular layer on head and body surround epithelium
--rhythmic contractions move sperm
-thick band of 3 layers in tail
--few contractions, but helps expel sperm
3. loose connective tissue rich in blood capillaries
functions of ductus epididymis
1. maturation of newly produced sperm during passage through duct
-acquire motility and ability to fertilize oocyte by addition of surface-associated decapacitation factor
2. reabsorption of remaining testicular fluid by epithelial cells (head and body)
3. phagocytosis of remaining residual bodies and sperm that degenerated in duct (head and body)
4. principal reservoir for mature sperm (tail)
5. expulsion of sperm during ejaculation in response to sympathetic stimulation of smooth muscle layers (tail)
-if sperm are not ejaculated they will degrade
straight tube with thick muscular wall that empties into prostatic urethra
-ascends along posterior border of testis and enters abdomen as part of spermatic cord which includes testicular artery, pampiniform plexus, and nerves
-distal end enlarges to form ampulla
-empties into prostatic urethra via ejaculatory duct
histological features of ductus deferens
-lined with pseudostratified columnar epithelium with sterocilia
--rounded basal cells sit on basal lamina
-lamina propria consisting of connective tissue rich in elastic fibers surrounds epithelium
-mucosa (epithelium + LP) forms longitudinal folds near distal end (near ampulla)
-thick layer of smooth muscle divided into inner and outer longitudinal layers separated by middle circular layer
--produces strong contractions that help expel spermatozoa during ejaculation
how is sperm transport from seminiferous tubules to ductuli efferentes, and from DE to urethra?
ST --> DE: passive (follows flow of testicular fluid)
DE --> U: active (beating cilia and muscle contraction
gross structure of seminal vesicles
elongated pair of tubular glands between posterior surface of bladder and rectum, superior to prostate
-parallel to ampulla of ductus deferens
-each has single convoluted tube that joins ampulla of ductus deferens to make ejaculatory duct
what are seminal vesicle secretions?
pale yellow viscous alkaline substance rich in fructose (primary energy source for sperm)
-contributes ~70% of volume of ejaculate
-forced into ejaculatory ducts via contraction of smooth muscle during ejaculation
-helps flush sperm through urethra
gross structure of prostate
largest accessory gland in male reproductive tract
-size and shape like walnut
-located inferior to urinary bladder and surrounds prostatic portion of urethra
-made of cluster of tubuloalveolar glands (not a single gland)
what are the 3 zones of the prostate?
1. transition zone - 5-10% of gland volume
-near prostatic urethra
-origin of 20% of prostate cancers
-origin of BPH
2. central zone - 25% of gland volume
-surrounds ejaculatory ducts
-origin of 1-5% of prostate cancers
3. peripheral zone - 70% of gland volume
-contains main prostatic glands
-origin of >70% of prostate cancers
-palpable during digital exam of rectum
where is prostatitis observed? what is involved in chronic prostatitis?
in all 3 zones of prostate
-usually involves bacteria or other infectious agents
histolotical structure of prostate
1. fibroelastic capsule rich in smooth muscle surrounds prostate and penetrates the parenchyma as septa divides it into ~40 lobules
2. prostate consists of 30-50 compound tubuloalveolar glands that open into prostatic urethra or prostatic sinus
3. glands are formed by pseudostratified epithelium
-basal cells - probably stem cells
-columnar secretory cells - produce secretions for ejaculate
-neuroendocrine cells - rare
4. epithelial structure and function depend on testosterone levels
5. fibromuscular stroma containing fibroblasts, smooth muscle cells, nerves, and blood vessels surrounds glands and is responsible for expulsion of prostatic fluid during ejaculation
what are prostatic concretions?
calcified prostatic secretions forming concentric condensations that are frequently observed in lumen of glands
-increase in number with age
prostatic fluid components?
thin milky acidic fluid made by columnar epithelial cells
-rich in citric acid and acid phosphatase
-contains proteolytic enzymes that liquefy semen
-contains serine protease (prostate specific antigen PSA)
extensive division of glandular epithelial cells forming nodular masses
-typically originates in transition zone leading to compression of urethra and difficulty urinating
-present in ~50% of men >50 yo, and ~95% of men >70 yo
-clinical symptoms evident in only 5-10% of cases
second most common cancer in men
-incidence increases with age (70% of men between 70-80 will develop disease, but majority of men will NOT die)
-PSA screening for presence and progression
--prostate cancer cells overproduce PSA and release it into circulation
--dramatically increased early detection of prostate cancer
--increased levels alone not diagnostic of cancer (needle biopsy required)
prostate cancer treatment
-if tumors restricted to prostate, "watchful waiting", surgery, radiation therapy, androgen suppression, or combo
-if tumors metastases, use androgen suppression (suppress testosterone production since cancer cells are typically dependent on testosterone)
gross structure of Bulbourethral (Cowper's) glands
pea-sized pair of glands located in urogenital diaphragm
-excretory duct of each gland joins initial portion of penile urethra
Bulbourethral glands secretion
clear akaline mucus-like substance
-discharged first during ejaculation to lubricate and neutralize penile urethra
glands of Littre (periurethral glands)
very small glands located along length of penile urethra
-secrete mucous-like fluid for lubrication
-fluids and spermatozoa from testes
-secretions from epididymis, bulbourethral glands, glands of Littre, prostate, and seminal vesicles
-alkaline to neutralize acidic environment of urethra and vagina
what is fresh ejaculate?
coagulum that gradually liquefies due to prostate secretions over a 5-25 minute period
what is the average ejaculate
~3 ml (2-6 ml)
-95% of volume from accessory glands
-100 million sperm/mL (range of 20-250 million/mL)
--only a few hundred reach ampulla region of oviduct where fertilization occurs