Male Reproductive System

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mse263
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245735
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Male Reproductive System
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2016-11-09 12:53:58
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MedFoundationsI Histology Exam4
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MedFoundationsI,Histology
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Histology Exam 4
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  1. Testes
    • are paired, located in the scrotum, & have both exocrine (sperm) + endocrine (sex hormones) functions
    • develop in the fetus under the control of testicular determining factor (TDF), a transcription factor from the sex-determining region of the Y chromosome (SRY)
    • testis develop in the posterior abdominal wall; are sent into scrotum & drag with it a bubble like structure called the tunica vaginalis, an extensions of the peritoneum
  2. Layer of the Testis
    • tunica vaginalis: outermost double-layered (extensions of the peritoneum)
    • tunica albuginea: inside the vaginalis, a dense fibrous CT capsule that thickens along the posterior surface to form the mediastinum testis
    • tunica vasculosa: underneath the albuginea, a loose CT layer containing blood vessels and lymphatics that invaginates into septa, dividing testes into compartments (lobules)
    • inside each lobule are 1-4 seminiferous tubules + interstitial tissue between the tubules

    • section of a testicle
    • tunica vasculosa septa divide internal area into lobules
    • in lobules are highly coiled seminiferous tubules
    • cross-section of seminiferous tubule
    • interstitial tissue surrounding seminiferous tubule is where blood vessel, lyphatics, & *Leydig Cells, which make testosterone, are located
    • sperm are made in the seminiferous tubules
  3. Leydig (Interstitial) Cells
    • secret testosterone, DHEA (dehydroepiandrosterone), & 5-alpha-androstenedione, a process controlled by LH & interstitial cell stimulating hormone (ICSH)
    • contain extensive SER, lipid droplets, lots of mitochondria, & a well-developed Golgi apparatus
    • found in space between seminiferous tubules, along w/ CT, nerves, blood, & lymphatic vessels
    • are derived from embryonic genital ridge mesoderm
    • can see proteinaceous crystals of Reinke in the cytoplasm
  4. Sertoli Cells (Supporting)
    • large cells that sit on basal lamina & their cytoplasm reaches all the way to the seminiferous tube lumen
    • they physically support the developing sperm, provide them with nutrients, & move them toward the lumen
    • controlled by FSH from the pituitary
    • they protect sperm by forming the blood-testis barrier which protects the spermatogenic cells from autoimmune attack
    • have lots of microvili; can change their shape
    • are derived from mesoderm
    • they phagocytose residual bodies shed by maturing spermatozoa
  5. What are some factors the sertoli cells secrete?
    • Androgen binding protein (to maintain high levels of testosterone for the proper development of sperm)
    • mullerian inhibitory factor (inhibits becoming a female)
    • activin (stimulates FSH secretion)
    • inhibin (acts on pituitary to decrease FSH secretion when there's excess T around)
    • K+ & HCO3-
  6. Spermatogonia
    • large, oval or round stem cells derived from primordial germ cells that are found on the basal lamina of seminiferous tubules
    • are diploid (2N chromosomes, 2N DNA)
    • when they divide they produce more stem cells + a terminally differentiated primary spermatocyte
  7. What are the only spermatogenic cell type present before puberty?
    Spermatogonia: small, round cells with oval to round nuclei that sit on the basal lamina
  8. Primary Spermatocyte
    • are the 2nd layer of cells up from the basal lamina
    • are large cells with a large nucleus that contains dark worm-like strands of heterochromatins
    • these cells are in PROPHASE OF MEIOSIS I (1st meiotic division)
    • when they divide to make 2ndary spermatocytes cross-over of chromosomes can occur to produce daughter cells which are genetically DIFFERENT from the somatic cells (& susceptible to immunological attack)
  9. Secondary Spermatocyte
    • are the 3rd layer of cells up from the basal lamina
    • they result from meiosis I & go on to complete the 2nd meiotic division (meiosis II) to produce spermatids
    • will not have to identify histologically because they rapidly divide to form spermatids, therefore are rarely visible
  10. Spermatids
    • are located next to the lumen
    • Early: small round cells with heterochromatic nuclei (jelly-filled donut)

    • Elongated (Late): condensed nuclei, tapered cell body, & have a flagellum
  11. Spermiogenesis
    • process of cytodifferentiation w/ extensive rearrangement of the cellular components but NO cell division is involved. Includes:
    • Acrosome formation: caps the nucleus opposite to where the tail develops
    • Centriole migration
    • Flagellum formation
    • Mitochondria migration: around the flagellum to provide energy for movement
    • Condensation of nuclear chromatin
    • Sloughing off residual bodies
  12. maturation phase of spermiogenesis
    • Centriole migration: both move to the spermatid’s posterior pole; 1 forms flagellum, other a collar around flagellum
    • Flagellum formation
    • Mitochondria migration
    • Condensation of nuclear chromatin
    • Sloughing off residual bodies: excess cytoplasm
    • (everything but acrosome formation)
  13. acrosome
    • a specialized lysosome that contains hyaluronidase, neuraminidase, acid phosphatase, trypsin-like protease, & other PAS-positive carbohydrate-rich components
    • it's enzymes help to penetrate the cells of the corona radiata & zona pellucida of the ovum during fertilization
  14. Spermatozoa (Sperm)
    • are released into the lumen and move into the ducts
    • are haploid & have long flagella
    • are the end product of spermiogenesis
    • made up of a head (nucleus w/ anterior 2/3s covered by acrosome) & tail
  15. Spermatozoa Tail
    • neck: has proximal centriole + base of flagellum
    • middle piece: mitochondria arranged in a spiral around the flagellum with a classical 9+2 arrangement of microtubules (axoneme)
    • principal piece: longest, 7 outer fibers + axoneme
    • end piece: no fibrous sheath & ends with 18 single microtubules
  16. Syncytial Development of Germ Cells
    • Type A Spermatogonia (stem cells): divide slowest, eventually commit to form a Type B Cell
    • Type B Spermatogonia (progenitor cells): divide mitotically & each daughter cell will have a cytoplasmic connection (incomplete cytokinesis but complete karyokinesis because the nuclei do split)
    • they give rise via spermatocytogenesis to Primary Spermatocytes
    • even through meiosis, all the cells are connected
    • means that GROUPS of spermatogonia develop at a certain period of time
    • get clonal nature of the seminiferous tubule
  17. clonal nature of sperm development
    • the fact that during division from spermatogenia to spermatids cells' nuclei divide completely however they remain attached to each other by small cytoplasmic bridges
    • these bridges don't break until the sperms are released into the lumen, helping to synchronize the release of a LARGE number of mature sperms at the same time rather than just 1 by 1
  18. Blood-Testis Barrier
    • protects the developing sperms from autoimmune attack
    • is made up of a belt of junctional complexes joining Sertoli cells at their lateral aspects & separates seminiferous tubule into 2 compartments: the (basal + abluminal) & adluminal compartment
  19. basal compartment
    • contains the spermatogonia & preleptotene spermatocyte (self, diploid)
    • IS ACCESSIBLE to any blood-borne substances that can get through the basal lamina
  20. adluminal compartment
    • reaches from the junctional complex to the lumen & houses primary & secondary spermatocyte & spermatids
    • it is INACCESSIBLE to blood-born substances except those that are taken up by the Sertoli cells & passed through gap junctions to the spermatogenic cells
    • In this compartment are primary spermatocytes onward (haploid, not self)
  21. hormone control
    • hypothalamic gonadotropin-releasing hormone (GnRH) mediates the episodic release of the gonadotrophins (LH and FSH) from the anterior pituitary
    • LH → Leydig cells: testosterone; feeds back negatively on GnRH & gonadotrophins production
    • FSH → Sertoli cells: ABP + tubule fluid
  22. Dihydrotestosterone (DHT)
    • a more potent androgen made from testosterone by 5 α-reductase
    • the form of a sex hormone used by accessory and external sex glands such as the prostate gland
    • 5 α-reductase can be targeted to inhibit DHT under certain circumstances, such as prostate cancer
  23. Where is testosterone aromatized by aromatase to produce estradiol (an estrogen)?
    in the peripheral tissues, eg. hypothalamus & adipose tissue to help accentuate the feedback mechanisms
  24. Prolactin in the male reproductive system
    potentiates the effects of LH on Leydig cells & may also play a paracrine role in cell proliferation & differentiation in the male reproductive tissues (eg. prostate)
  25. Cryptorchism
    • condition in which one or both testes failed to descend into the scrotal sacs
    • sperms will not develop properly in the test is subjected to higher temperature
    • fertility rate in unilateral cryptorchism is about 50%, but fertility rate in uncorrected bilateral cryptorchism is nearly zero
    • it increases the risk of testicular cancer in the undescended testis
  26. Order
    • Seminiferous Tubules (end in narrow termini that're only Sertoli cells)
    • Straight Tubules →
    • Rete Testis (mediastinum)
    • Efferent Ductules (only a small part is intratesticular, the rest is outside forming the head of the epididymis) →
    • Epididymis →
    • Ductus Deferens →
    • Ampulla of ductus deferens →
    • Ejaculatory duct
  27. Efferentes Ductules
    • connect the Rete Testis (which is where sperm have moved from the seminiferous & then straight tubules) to the Epididymus
    • border: pseudostratified columnar, short cells, & tall ciliated cells (only place with real cilia in male tubules) that transport non-motile sperm
    • have a star shaped lumen
    • where most of the fluid from the testis is resorbed (concentration happens)
  28. Efferentes Ductules
    • note the wavyness of tissue (tall/short/tall/short) surrounding the lumen - can be used to differentiate Efferentes Ductules from seminiferous tubules
    • tall cells are ciliated to move the sperm along the tubule b/c they can't swim yet
    • in the center (lumen) of a cross-section of an excurrent duct you see sperm heads & residual bodies
  29. Ductus Epididymis
    • a single, highly coiled, long tube that can be divided into the head (caput), body (corpus) & tail (cauda)
    • where sperm enter from the efferentes ductules
    • an important site for sperm, transport, storage, protection, & maturation whose cells are also involved in phagocytosis of residual bodies
    • sperm are moved slowly forward by peristaltic contractions of the muscles
    • Ductus Epididymis
    • has pseudostratified epithelium with tall columnar cells with stereocilia (super long microvili) at their apical end
    • has a super smooth surface
    • basal reserve cells are present
    • can see surrounding walls made of smooth muscle which gradually thickens along the length of the tube
    • can see sperm in cross sections of the lumen
    • purpose of the epididymis is to secrete products for sperm maturation
  30. What is the purpose of the stereocilia on epididymus cells?
    • the epididymus' pseudostratified epithelium with tall columnar cells have apical (facing the lumen) stereocilia
    • these are long NON-motile microvilli that absorb extra fluid mixed in with sperm, concentrating the sperm and beginning their maturation process
  31. What does the epithelium of the ductus epididymis secrete?
    • factors such as citrate, fructose, vitamin C to nourish the sperm as well as:
    • 1. sialic acid
    • 2. glycerophosphoryl choline
    • 3. forward motility protein - allows sperm to SWIM straight by the end of the epididymis
    • the proper function of the epididymis depends on testosterone and there is a high concentration of androgen binding protein in the epididymis
  32. How long does it take for sperms to move through the epididymis?
    • about 12 days - they are stored there
    • by the time they move into the next structure, they have acquired nearly (but not all) the features necessary to fertilize an egg
  33. Ductus Deferens
    • a single straight tube with thick muscular walls the epididymis empties into & its other end opens into the ejaculatory duct
    • it runs in the spermatic cord between the testis & the inguinal canal then proceeds by itself toward the seminal vesicle & prostate
    • it contracts strongly during ejaculation
    • this is what's snipped to make men infertile
  34. Ductus Deferens
    • has a lumen with mucosal folds (more irregular than epididymis)
    • its lining is pseudostratified columnar epithelium with FEWER stereocilia than in the epididymis (most absorption has already taken place)
    • basal reserve cells are present
    • its wall contains 3 layers of smooth muscles (inner longitudinal, middle circular, outer longitudinal)
    • travels into pelvic cavity, where there's a swelling of it known as the Ampulla & then it ends in the ejaculatory duct (right where the seminal vesicles appear)
  35. What is present in the spermatic cord between the testis and the inguinal canal?
    • 1. ductus deferens
    • 2. blood vessels (eg. testicular arteries & pampiniform plexus)
    • 3. skeletal muscle (cremaster muscle - derived from abdominal wall muscle)
    • 4. testicular artery
  36. Where is the thickest muscular wall found in the In the male genital tract?
    • deferent duct (ductus deferens)
    • it has 3 layers of smooth muscle in its wall to propel sperm toward accessory glands where secretions are added resulting in semen
  37. Pampiniform Plexus of Veins
    • complex of veins that return from the testes which also function to regulate their temperature
    • arteriole blood traveling to the testis is warm, so the pampiniform plexus acts as a heat exchanger absorbing heat from blood in adjacent arteries, cooling the blood
    • an abnormal enlargement of the pampiniform plexus is called varicocele

  38. Accessory Sex Glands
    • contribute secretions to a large portion of the semen & help to stabilize, nourish, & propel sperm
    • they depend on dihydrotestosterone (DHT) for proper function
  39. Seminal Vesicles
    • paired structures each made up of a highly coiled 15cm long tube
    • the mucosa is highly folded with complicated BRANCHING
    • epithelial cells contain lots of secretory granules + yellowish lipid droplets
    • its secretions make up a large portion of the semen & are rich in fructose, inositol, ascorbic acid, prostaglandins, seminogelins I & II, & pigment (flavins)
    • secretions COAGULATE semen
    • under the lamina propria are smooth muscles which contract during ejaculation
    • it opens into the ejaculatory duct
    • *sperm is NOT stored here (stored in epididymus)
  40. Seminal Vesicle
    • coiled tube
    • highly infolded mucosa ('brain coral')
    • pseudostratified columnar epithelium with basal stem cells
    • can see smooth muscle surrounding layer that contracts during ejaculation
    • can see lipid droplets in epithelium under high magnification - show up in puberty
  41. Prostate Gland
    • seminal vesicles open into the prostate
    • parenchyma (functional part) consists of 3-50 compound tubuloalveolar glands w/ the ducts emptying independently into the urethra (which is continuous with the bladder)
    • the pseudostratified columnar epithelium contains secretory & basal cells
    • the epithelium produces alkaline prostatic fluid via apocrine secretion, rich in PSA, fibrinolysin, citric acid, zinc*
    • its stroma is dense & fibromuscular: contains smooth muscle cells + CT [can stain for smooth mus. actin]
  42. Prostate Parenchyma Zones
    • (from outside to inside)
    • Peripheral: 70% of gland, where carcinoma usually develops
    • Central: 25% of gland, resistant to carcinoma & inflammation
    • Transitional: where BPH develops
    • Periurethral: where BPH develops
  43. Carcinoma of the Prostate
    • cancer that usually arises in the PERIPHERAL zone of the prostate, classically in a posterior location, thus palpable on rectal exam
    • most common form of cancer in men and the 2nd leading cause of cancer death
    • is usually found in men above 50 years of age
    • In the normal prostate, basal cells form a complete ring around secretory cells; they're ABSENT in cancerous tissues
  44. Benign prostatic hyperplasia (BPH)
    • an increase in both the parenchymal and stromal components of the prostate
    • usually arises in the TRANSITIONAL zone of men above 50 years of age (is very common)
    • hyperplastic nodules later develop in the Periurethral zone & may encroach upon the urethra & affect urination
    • results in trouble urinating
  45. Prostatic acid phosphatase (PAP)
    a tissue specific marker
  46. Prostate specific antigen (PSA)
    • a proteolytic enzyme that helps to liquefy the semen which coagulates after ejaculation
    • high levels can be used to identify a potential carcinoma/cancer
  47. What is the largest of the male accessory sex glands?
    the prostate
  48. Bulbourethral Gland (Cowper)
    • paired, small tubuloalveolar accessory sex glands lined by CUBOIDAL epithelium
    • they secret a clear, alkaline, sialoprotein-rich mucus into the Membranous Urethra (the portion of the urethra which runs through the urogenital diaphragm) during sexual excitation
    • the secretion lubricates the urethra before ejaculation
    • Bulbourethral Gland
    • mucus secreting cells
    • basally located nucleus
    • pale cytoplasm
  49. Urethral Glands (of Littre)
    • tiny openings throughout penile urethra
    • might be periurethral or intraepithelial
    • have to open into the lumen
    • constitutively lubricating the urethra (for the passage of urine & other things)
  50. Urethra has 3 different parts
    • epithelium is transitional near the bladder
    • then there’s a stratified epithelium part
    • then farther along it’s SSNKE
    • at the very end it’s SSKE
  51. primary spermatocytes
    (4N; 92; tetraploid) formed from spermatogonial stem cells dividing by mitosis; are initially diploid and are undergo meiosis
  52. secondary spermatocytes
    (2N; 46; diploid) primary spermatocytes that have undergone meosis I; they undergo a meiosis II which results it HAPLOID spermatids
  53. one primary spermatocyte produces:
    four spermatids
  54. spermiogenesis
    • the process by which spermatids are remodeled to form mature sperm (spermatozoa)
    • elongation, tail development, cytoplasm shed
  55. Penile urethra
    • urethra that runs through the penis
    • has a stratified cuboidal epithelium (that can changes into stratified squamous when inflamed, possibly cancerous)
    • small Littre glands that contain mucus secretory cells can be found in the periurethral tissue or in the epithelium (intraepithelial)
    • the mucus secretion helps to lubricate the urethra solely to move URINE out of the urethra (not sperm)

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