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MS 1 Unit 7 Microscopic Anatomy > Male Reproduction > Flashcards

Male Reproduction Flashcards

1
Q

Gross Anatomy of Testis

A
  • lie in scrotum, suspended by the spermatic cords
  • scrotum maintains the testes at 2C below body temp which is essential for sperm production
  • testes descend from abdomen into scrotum via inguinal canal at 26 weeks
  • anterolateral surface covered by tunica vaginalis an extension of the abdominal peritoneum
  • blood from testicular artery which is highly convoluted near the testis
  • pampiniform venous plexus carries blood away
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2
Q

Tunica vaginalis

A
  • serous sac (simple squamous epithelium) consisting of outer parietal and inner visceral layers
  • visceral layer adheres to tunica albuginea on anterolateral surface of testis
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3
Q

Tunica Albuginea

A

-thick capsule of dense irregular connective tissue covering each testis

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4
Q

Mediastinum Testis

A
  • thickening of the tunica albuginea on the posterior surface
  • vessels and ducts pass through it as they enter or leave the testis (no tunica vaginalis here)
  • projects inward giving rise to incomplete septa which divide each testis into 250 lobules
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5
Q

Testicular lobules

A
  • 1-4 seminiferous tubules per lobule loose connective tissue stroma
  • interstitial tissue containing blood vessels, lymphatics, nerves and Leydig cells
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6
Q

Seminiferous tubules

A
  • where spermatozoa are produced

- each forms a convoluted U-shaped loop beginning and ending near the mediastinum

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7
Q

Tubuli Recti (straight tubules)

A

-short tubules within mediastinum that connect seminiferous tubules with rete testis

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8
Q

Rete testis

A

-anastomotic network of channels in the mediastinum

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9
Q

Ductuli efferentes (efferent ductules)

A

-10-20 ducts that connect rete testis to epididymis

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10
Q

Seminiferous Tubules

A
  • long 30-70 cm convoluted tubule lined with a complex stratified germinal epithelium (seminiferous epithelium) containing a wall-defined basal lamina
  • surrounded by a fibrosus tunica propria layers of fibroblasts and myoid cells
  • myoid cells have contractile properties that help move spermatozoa and testicular fluid through seminiferous tubules
  • spermatogenic cells- germ cells (proliferating)
  • Sertoli cells- supporting cells (non-proliferating)
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11
Q

Spermatogenesis

A
  • formation of haploid spermatozoa (spermatozoids or sperm) from the undifferentiated diploid germ cell, the spermatogonium
  • occurs in an inward direction from basal lamina toward lumen
  • takes 64 days
  • requires testosterone which is secreted by Leydig cells in the interstitial tissue (normal adult testes make >100 million sperm/day)
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12
Q

Spermatogonia

A
  • diploid
  • type A spermatogonia- continue dividing as stem cells
  • type B spermatogonia- progenitor cells that differentiate into primary spermatocytes increase their number through mitotic cell division
  • daughter cells remain attached to each other via cytoplasmic bridges; allows coordination of spermatogenesis events between cells because of communication via these bridges
  • histology: round cells sitting on basal lamina; heterochromatic (dark) nuclei
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13
Q

Primary spermatocytes

A
  • diploid
  • mitotic division of type B spermatogonia followed by DNA replication enter prophase of first meiotic division soon after formation; prophase takes 22 days
  • genetic material is exchanged between paired homologous chromosomes (recombination) to generate genetic diversity prior to first meiotic division (reduction division)
  • 4 haploid gametes
  • largest germ cells, large nuclei containing thick strands of condensed chromatin
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14
Q

Secondary spermatocytes

A
  • haploid
  • generated by meiotic division of primary spermatocytes (reduction division)
  • very short lived so difficult to find in sections
  • cells immediately enter prophase without synthesizing new DNA (no S phase)
  • undergo second meiotic division; sister chromatids separate into the resulting 2 spermatids
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15
Q

Spermatids

A
  • haploid
  • differentiate into spermatozoa via spermiogenesis
  • histology: small cells that are numerous near lumen of seminiferous tubule; early spermatids have small condensed nuclei; late spermatids have highly condensed nuclei
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16
Q

Spermiogenesis

A
  • final step of spermatogenesis, no cell division, happens when spermatids are attached to Sertoli cell plasma membrane
    1) 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 the acrosomal cap (acrosome) which contains hydrolytic enzymes that dissociate cells of the corona radiate and digest the zona pellucida of the oocyte
    2) flagellum formation- centrioles migrate from next to nucleus to a position near cell surface opposite the forming acrosome; one centriole initiates assembly of microtubules, forming flagellum; mitochondria aggregate around proximal part of flagellum forming middle piece where swimming movement is generated
    3) nuclear chanes- nucleus condenses, elongates, and moves anteriorly displacing cytoplasm posteriorly
    4) change in orientation- halfway through spermiogenesis, the spermatid reorients itself so head points toward basal lamina and developing flagellum extends into lumen
    5) later changes- 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, a process termed spermiation
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17
Q

Structure of Spermatozoa

A
  • head-flattened and pointed; consists primarily of highly condensed nucleus with anterior two-thirds covered by acrosomal cap containing enzymes required for penetration of zona pellucida of oocyte
  • Midpiece- contains mitochondria wrapped around flagellar axoneme
  • Tail-contains fibrous sheath wrapped around flagellar axoneme
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18
Q

Histological Features of Sertoli Cells

A
  • tall columnar non-replicating epithelial cells
  • adhere to basal lamina and can extend to lumen of tubule
  • apical and lateral processes envelope spermatogenic cells; difficult to see cell outline
  • euchromatic nucleus is ovoid or triangular with deep infolding and a prominent nucleolus; shape and location of nucleus varies considerably
  • connected very tightly to neighboring Sertoli cells via occluding junctions at basolateral part of cell; these 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
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19
Q

Functions of Sertoli Cells

A
  • support, protection and nutrition to developing spermatozoa which are isolated from blood supply by blood testis barrier (mediate exchange of nutrients and metabolites)
  • phagocytosis- of residual bodies shed from spermatids and degenerating spermatogenic cells that failed to differentiate completely
  • secretion of testicular fluid into lumen 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
  • 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; sperm specific antibodies in semen can result in infertility because they may cause sperm to agglutinate, impairing their movement
20
Q

Interstitial Tissue

A
  • consists of connective tissue, nerves, blood vessels, and lymphatics
  • connective tissue includes Leydig cells, fibroblasts, macrophages and mast cells
21
Q

Leydig cells

A
  • steroid secreting cells that become apparent during puberty
  • large rounded or polygonal cells
  • central nucleus
  • eosinophilic cytoplasm due to extensive smooth ER; rich in lipid droplets produce nearly all testosterone in males (<5% is produced by adrenal gland)
  • stimulated to produce testosterone by LH released by anterior pituitary
22
Q

Testosterone

A
  • produced for 4 months of gestation then Leydig cells remain quiescent until puberty when they are reactivated and remain active throughout life
  • high concentration (200x circulating concentration) is required for spermatogenesis in seminiferous tubules; androgen binding protein secreted by Sertoli cells concentrates testosterone in seminiferous tubules
  • acts on Sertoli cells to help stimulate spermatogenesis
  • required for growth, development and maintenance of accessory reproductive glands; it also influences development of secondary sex characteristics and sexual behavior
23
Q

Factors affecting spermatogenesis

A
  • dietary deficiencies
  • general or local infections
  • systemic diseases (fever, kidney disease, metabolic disorders)
  • steroid hormones and related medications (decrease FSH secretion)
  • toxic chemicals (pesticides, plastics, PCBs)
  • ionizing radiation
  • elevated testicular temperature- hot tubs or cryptorchidism
  • the non-dividing Sertoli and Leydig cells and the reserve stem cells, which have little mitotic activity, are less vulnerable to dietary deficiencies and mutagenic agents than the dividing and differentiating germ cells
24
Q

Intratesticular Ducts

A

-intratesticular ducts carry spermatozoa and fluid from seminiferous tubules to the epididymis

25
Q

Tubuli recti (straight tubules)

A

-short tubes that join seminiferous tubules to rete testis lined with epithelium consisting of only Sertoli cells or simple cuboidal cells supported by a dense connective tissue sheath (no spermatogenic cells present)

26
Q

Rete testis

A
  • anastomotic network of channels connecting tubuli recti to ductuli efferentes located within mediastinum
  • lined with simple epithelium that varies from squamous to low columnar
  • produces some testicular fluid for sperm transport (Sertoli cells also produce this fluid)
27
Q

Ductuli efferentes (efferent ductules)

A
  • 20 ducts connecting rete testis to epididymis lined with simple epithelium that appears scalloped due to alternating groups of cells
  • non-cilated cuboidal (or low columnar) cells with microvilli on apical surface- absorb most of the testicular fluid produced in seminiferous tubules
  • ciliated tall columnar cells- contain the only true cilia in the male reproductive system, cilia beat in direction of epididymis sweeping spermatozoa along in that direction
28
Q

Excretory Ducts

A

-carry spermatozoa from the scrotum to the penile urethra during ejaculation and include the ductus epididymis, the ductus deferens and the urethra

29
Q

Epididymis

A
  • crescent shaped structure on superior and posterior surfaces of testis
  • divided into head, body and tail; spermatozoa enter at head (on superior surface of tesis)
  • consists of a single highly coiled tube (ductus epididymis) and associated smooth muscle cells and loose connective tissue
30
Q

Structure of Epididymis

A
  • ductus epididymis is a highly coiled tube lined with pseudostratified columnar epithelium composed of basal cells- rounded stem cells sitting on basal lamina; principal cells- tall columnar cells with sterocilia and basally located nuclei smooth muscle cells surround the ducus epididymis
  • head and body- thin circular layer of smooth muscle surrounds epithelium; rhythmic contraction of these muscle cells helps move sperm
  • tail- inner and outer longitudinal layers of smooth muscle present on either side of circular layer; few rhythmic contractions during ejaculation expels sperm
  • loose connective tissue
  • rich in blood capillaries
31
Q

Functions of Ductus Epididymis

A
  • maturation of newly produced sperm during passage through duct- acquire motility, acquire ability to fertilize an oocyte in female reproductive tract prior to fertilization)
  • reabsorbtion of remaining testicular fluid by epithelail cells (in head and body)
  • phagocytosis of remaining residual bodies and sperm that degenerated in duct (in head and body)
  • principal reservoir for mature sperm (tail)
  • expulsion of sperm during ejaculation in response to sympathetic stimulation of smooth muscle layers (tail)- if sperm are not eventually ejaculated, they will gradually degrade
32
Q

Ductus Deferens (vas deferens)

A
  • 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
33
Q

Histological Features of Ductus Deferens

A
  • narrow lumen
  • lined with pseudostratified columnar epithelium with stereocilia- rounded basal cells sit on basal lamina
  • lamina propria consisting of connective tissue rich in elastic fibers surrounds epithelium mucosa (epithelium and lamina propria) forms longitiduinal folds near distal end (near ampulla)
  • thick layer of smooth muscle divided into inner and outer longitudinal layers separated by a middle circular layer-produces strong contractions that help expel spermatozoa during ejaculation
  • sperm transport is passive from seminiferous tubules to ductile efferentes (follows flow of testicular fluid) and active from ductuli efferentes to urethra (beating cilia and muscle contraction)
34
Q

Accessory Genital Glands

A

-the accessory genital glands make secretions that are essential for male reproductive function

35
Q

Gross Structure of Seminal Vesicles

A
  • elongated pair of tubular glands
  • located between the posterior surface of the urinary bladder and the rectum, superior to the prostate gland
  • parallel to the ampulla of the ductus deferens
  • each vesicle consists of a single highly convoluted tube ending in a short excretory duct that joins the ampulla of the ductus deferens to form the ejaculatory duct
36
Q

Secretion from Seminal Vesicles

A
  • pale yellow viscous alkaline substance rich in fructose, the primary energy source for sperm
  • contributes 70% of the volume of the ejaculate
  • force into ejaculatory ducts via contraction of smooth muscle during ejaculation
  • helps flush sperm through urethra
37
Q

Gross Structure of Prostate

A
  • largest accessory gland in the male reproductive tract
  • size and shape similar to a walnut
  • located inferior to urinary bladder and surroudns prostatic portion of urethra
  • composed of a cluter of tubuloalveolar glands (not a single gland)
38
Q

Zones of prostate

A 
1) transition zone:
5-10% of gland volume
near prostatic urethra
origin of 20% of prostate cancers
site of origin of benign prostatic hyperplasia (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

-inflammation (prostatitis) can be observed in all 3 zones of the prostate

39
Q

Histology of Prostate

A
  • fibroelastic capsule rich in smooth muscle surrounds prostate and penetrates the parenchyma as septa to divide it into 40 lobules
  • prostate consists of 30-50 compound tubuloalveolar glands that open into the prostatic urethra or prostatic sinus
  • glands are formed by pseudostratified epithelium: basal cells- probably stem cells, columnar secretory cells-produce secretions for ejaculate, neuroendocrine cells-rare
  • epithelial structure and function depend on testosterone levels
  • fibromuscular stroma containing fibroblasts, smooth muscle cells, nerves and blood vessels surrounds glands and is responsible for expulsion of prostatic fluid during ejaculation
  • prostatic concretions are calcified prostatic secretions forming concentric condensations that are frequently observed in lumen of lands; they increase in number with age
40
Q

Secretion (prostatic fluid)

A
  • thin milky acidic fluid produced by columnar epithelial cells
  • rich in citric acid and acid phosphatase
  • contains proteolytic enzymes that liquefy the semen
  • contains a serine protease known clinically as prostate specific antigen (PSA)
41
Q

Chronic Prostatis

A

-usually involves bacteria or other infectious agents

42
Q

Benign Prostatic Hypertrophy, BPH

A
  • extensive division of glandular epithelial cells forming nodular masses
  • typically originates in transition zone and may lead to compression of urethra and difficulty with urination
  • present in 50% of men >50 years old and 95% of men > 70 years old
  • clinical symptoms evident in only 5-10% of cases
43
Q

Prostate Cancer

A
  • second most common cancer in men
  • incidence increases with age; 70% of men between 70 and 80 will develop this disease
  • majority of men with this disease will NOT die of their disease
44
Q

PSA

A
  • PSA produced by epithelium of prostate is normally only release into prostatic fluid
  • in prostate cancer, circulating PSA increases due to its increased production and release from prostatic cancer cells
  • PSA testing has dramatically increased early detection of prostate cancer when the tumors are still localized to the prostate
  • prior to PSA testing, which began 1995, tumors were rarely detected early because they typically form in peripheral zone and do not impinge on the prostatic urethra; therefore, they were often inoperable by the time they were detected
  • increased PSA levels alone are not diagnostic of cancer; increased PSA levels can occur with BPH and inflammation of the prostate, so a diagnosis of prostate cancer requires a needle biopsy
  • for tumors restricted to the prostate, treatment are watch waiting, surgery, radiation therapy, androgen suppression, or combo
  • for advance cancer with metastases, androgen suppression
45
Q

Bulbourethral Glands (Cowper’s Glands)

A
  • pea sized pair of glands located in the urogenital diaphragm
  • excretory duct of each gland joins the initial portion of the penile urethra
  • clear alkaline mucus-like substance
  • discharged first during ejaculation to lubricate and neutralize penile urethra
46
Q

Glands of Littre (periurethral Glands)

A
  • very small glands located along the length of the penile urethra
  • secrete mucous-like fluid for lubrication
47
Q

Semen

A
  • fluids and spermatozoa from the testes, and secretions for the epididymis, bulbourethral glands, glands of Littre, prostate and seminal vesicles. It is alkaline which may help neutralize the acidic environment of the urethra and vagina. Fresh ejaculate is a coagulum that gradually liquefies over a 5-25 min period
  • average ejacuate: 3 ml, 95% of volume is accessory glands, 100 million sperm per ml (range of 20-250 million per ml)
  • only a few hundred sperm reach the ampulla region of the oviduct where fertilization occurs
  • ejaculation order of events:
    1) bulbourethral glands and glands of Littre release a very small amount of a mucus-like fluid for lubrication
    2) prostate secretions are expelled along with spermatozoa from the epididymis and ductus deferens
    3) seminal vesicle fluid is expelled to flush the sperm through the urethra

MS 1 Unit 7 Microscopic Anatomy (4 decks)

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