Tag Archives: tunica albuginea

36. The anatomy, histology and development of the ureter, urinary vesicle and urethra.

6 Jan

36. The anatomy, histology and development of the ureter, urinary vesicle and urethra.

Anatomy of the ureter, urinary vesicle and urethra.

Ureter

*retroperitoneal
General Info:
musc tube that transmit urine via peristaltic waves, leads from kidney

is the most posterior structure that emerges from hilus of kidney
25-30 cm long
enter bladder @ anteromedially, superior to levator ani

Topography:

  • crosses bifurcation of common iliac a @ pelvic brim
  • desc retroperitoneally on lat pelvic wall –> med to umbilical a & obturator a/v
  • post to ovary @ post surface of ovarian fossa
  • 1-2 cm lat to uterus, runs w/ uterine a, which runs above and ant to base of broad lig
  • passes post/inf to ductus deferens & lies in front of seminal vesicle before entering post/lat bladder (male)


2 parts – abdominal/pelvis


Abdominal

crossed by 3 structures: Topography
1. Gonadal a/v – in front
2. Psoas major – behind
3. Bifurcation of common iliac a w/ ureter in front of int iliac a

Male – ductus deferens crosses ureter in front

Female

  • uterine a crosses in front
  • @ bifurcation of common iliac, forms post border of ovarian fossa
  • contacts lat fornix of vagina b4 entering bladder

Blood Supply:

  • rec blood from aorta, renal, gonadal, common & int iliac, umbilical, sup/inf vesicle a, middle rectal a
  • Vesicle venous plexus –> int iliac v (sometimes, prostatic vesicle plexus)

Lymph Drainage: lumbar, common iliac, ext iliac, int iliac l.n

Urinary Bladder


*Infraperitoneal – lower in female
located in pelvis minor when empty
located full, can enter major pelvis –> even up to umbilicus

General Info:

  • THICK muscular wall = detrusor m
  • holds urine, until ready to release it
  • mucus membrane attaches, except @ trigone
    • mucus membrane attaches to CT underlying, no mucosal folds
    • originates from mesonephric duct
    • marked by entrances of ureter & ejaculatory duct
    • has 2 ureteric openings and urethral openings (int urethral sphincter)
  • anchored by CT ligaments = paracysticum
  • held @ neck  to pubic bone, via puboprostatic (male), or pubovesical (female) ligaments

Structure of Bladder (Detail):

The bladder itself consists of 4 layers:-

(1) Serous – this outer layer being a partial layer derived from the peritoneum,
(2) Muscular – the detrusor muscle of the urinary bladder wall, which consists of 3 layers incl. both longitudinal and circularly arranged muscle fibres,
(3) Sub-mucous a thin layer of areolar tissue loosely connecting the muscular layer with the mucous layer
(4) Mucous – the innermost layer of the wall of the urinary bladder loosely attached to the (strong and substantial) muscular layer. The mucosa falls into many folds known as rugae when the bladder is empty or near empty.

  • The features observable on the inside of the bladder are the ureter orifices, the trigone, and the internal orifice of the urethra.
  • The trigone is a smooth triangular region between the openings of the two ureters and the urethra and never presents any rugae even when the bladder is empty – because this area is more tightly bound to its outer layer of bladder tissue.

Peritoneal relations of bladder:

Outer surfaces of the Bladder: The upper and side surfaces of the bladder are covered by peritoneum (also called “serosa”). This serous membrane of the abdominal cavity consists of mesthelium and elastic fibrous connective tissue. “Visceral peritoneum” covers the bladder and other abdominal organs, while “parietal peritoneum” lines the abdomen walls.

Topography of Bladder: Bladder Bed

  • ant = pubic bone, separated from ant ab wall & pelvis by rectopubic space
  • inf/lat = obturator int m, levator ani m
  • inf/post = rectum

B/w bladder & rectum:
Male – seminal vesicles & ejaculatory duct, ductus deferens
Female – uterus & upper vagina

female-sagittal-section

Vesicouterine Pouch:
ant = bladder
post = uterus
lat = vesicouterine ligaments (folds)

Normally, pouch so small, there is nothing in it
If Rectoversion occurs, may contain SI loops
bladder connected to CT except @ neck where puboprostatic lig anchors it (male)

Rectovesicle Pouch:
ant = bladder, seminal vesicle, DD
post = rectum
lat = rectovesicular fold

In male, pertioneum covers fundus, reflecting from upper post wall, and covers tip of seminal vesicle

male-sagittal-section

Parts of Bladder:

  1. Apex (ant end)
    • retro to symphysis
    • origin of median umbilical ligament – remnant of embryonic urachus (connection b/w urinary bladder and embryonic allantois)
  2. Fundus (post/inf)
    • contact w/ rectum in male, separated by rectovesicular septum
    • contacts w/ ant surface of vagina in female
  3. Neck (lat/post — converges here)
    • urethra originates from bladder here
    • just above = uvula – small eminence projects into urethra

Blood Supply:

  • Sup vesicle a (int iliac a)
  • Fundus of bladder
    • inf vesicle a (Male)
    • vaginal a (uterine a – Female)
  • veins = vesicle venous plexus –> int iliac v (prostatic venous plexus)

Lymph Drainage:

  • body = ext iliac lymph nodes
  • fundus = int iliac l.n
  • neck = sacral & common iliac l.n.

Innervation:

  • PNS from pelvic splanchnic n (S2-4)
    • VM for detrusor m
    • (-) for int urethral sphincter
  • SNS (T12-L2)
    • VM for int urethral sphincter
    • (-) detrusor m

Urethra
From bladder –> opens @ perineum, urine emptied thru it

Male Urethra


Parts to it:
1. Prostatic urethra
3 cm long, and w/in prostate
widest part of urethra
covered w/ urothelium = transitional epithelium

The prostatic urethra begins at the neck of the bladder and includes all of the section that passes through the prostrate gland. It is the widest and most dilatable part of the male urethral canal.

Structures opening here:
1. Prostatic glands
2. Ejaculatory ducts
3. Prostatic utricle

long ridge = urethral crest

  • runs through out w/ 2 grooves beside it = prostatic sinuses
  • opening of submucosal ducts & prostatic glands
  • @ upper crest = seminal collicus

Seminal colliculus

  • small hill like structures protruding into urethra
  • lat to colliculus are prostatic sinuses, where prostate glands open
  • 3 small openings:
    • @ midline = utricle of prostate (remnant of paramesonephric duct – regresses in male)
    • inf to that = 2 ejaculatory ducts

secretions of prostate, seminal vesicle, and bulbourethral glands mixes w/ spermatozoa from testis = semen

2. Membranous urethra
1 cm long
passes thru UG diaphragm – here ext urethral sphincter seen

The membranous urethra is the shortest and narrowest part of the male urethra. This section measures approx. 0.5 – 0.75 inches (12 – 19 mm) in length and is the section of the urethra that passes through the male urogenital diaphragm.
The external urethral sphincter (muscle) is located in the urogenital diaphragm (as for the female urethra).
The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS).

3. Penile urethra
enters bulbous part of  penis
Pathway: turns up @ sharp angle (1st turn)  –> runs along bulb of penis –> to pubic symphysis –> bends down (2nd turn) –> corpus spongiosum –> runs down to tip of penis & opens @ navicular fossa

The spongy (penile) urethra is the longest of the three sections. It is approx. 6 inches (150 mm) in length and is contained in the corpus spongiosum that extends from the end of the membranous portion, passes through the penis, and terminates at the external orifice of the urethra – which is the point at which the urine leaves the body.

@ navicular fossa: str columnar –> str sq non keratinazing epith

CLINICAL NOTE: B/c of 2 sharp bends – makes it difficult to insert catheter

Blood supply: prostatic br of inf vesicle a & middle rectal a, v follow a

Lymph Drainage: int/ext iliac l.n

Nerve supply: pudendal n, prostatic plexus (inf hypogastric plexus)

male-urethra

Female urethra

female-urethra

At only about 1.5 inches (35 mm) long, the female adult urethra is shorter than the adult male urethra (approx. or 8 inches, or 200mm). The female urethra is located immediately behind (posterior to) the pubic symphysis and is embedded into the front wall of the vagina.

The urethra itself is a narrow membranous canal that consists of three layers:

  1. Muscular layer – continuous with the muscular layer of the bladder, this extends the full length of the urethra.
  2. Thin layer of spongy erectile tissue – including plexus of veins and bundles of smooth muscle fibres. Located immediately below the mucous layer.
  3. Mucous layer – internally continuous with the bladder and lined with laminated epithelium that is transitional near to the bladder.

After passing through the urogenital diaphragm (as shown in the diagram), the female urethra ends at the external orifice of urethra – which is the point at which the urine leaves the body. This is located between the clitoris and the vaginal opening.

The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS).

The female urethra is a much simpler structure than the male urethra because it carries only urine (whereas the male urethra also serves as a duct for the ejaculation of semen – as part of its reproductive function
upper 1/2 = prostatic urethra
lower 1/2 = “membranous”

@ upper part = Paraurethral glands –> ducts @ ext urethral orifice

@ lower part
goes through UG diaphragm
transverse perineal m wraps around to form = urethro vaginal sphincter
closely associated w/ ant wall of vagina

  • attached via strong CT sheath = urethrovaginal septum
  • b/w them = urethrovaginal space

Blood supply: int pudendal a, vaginal a, veins follow a

Lymph Drainage: sacral/int iliac l.n

Nerve supply: pudendal n


Process of Urination:
Initiated by (+) of stretch receptors in detrusor m in bladder in wall by inc volume of uring
innervated by S2-4 via pelvic splanchnic n
can be assisted by contraction of abdominal m = inc intra abdominal & pelvic pressures

Process:
1. SNS = (+) relaxation of bladder wall
contract inner sphincter –> (-) emptying
may stimulate detrusor m to prevent reflux of semen into bladder during ejaculation

2. PNS = preggl fibers in pelvis splanchnic n
synapse in pelvic (inf hypogastric plexus)
post ggl to bladder musc induc reflex = contraction of detrusor m
and relaxation of int sphincter
inc urge to urinate

3. SM fibers in pudendal n cause voluntary relaxation of ext urethral sphincter
bladder begins to release

4. @ end of urination
the ext urethral sphincter ( & bulbospongiosus m in male) contracts
expel the last few drops of urine from urethra

Histology  of the ureter, urinary vesicle and urethra.

Slide #63 Ureter * H&E


Structures to Identify:

  • 3 layers = mucosa, muscularis, adventia
  • transitional epith
  • umbrella cells
  • a/v
  • CT
  • piriform cells
  • basal cells

General Info

  • paired tubular structures that convey urine from kidney –> bladder
  • lined w/ transitional epith to adapt to changing environment (fluid v no fluid)

Mucosa

  • Epith = urothelium
    • thick, with cells that change shape
  • star shaped irregular lumen, made by mucosal folds, due to musc. contractions
  • Note that lumen is long , narrow and star shaped, not circular *like DD
  • 3 main cell types of Epith
    • umbrella cells – come in contact with urine, and adjust accordingly, can be bi-nucleated, shape change due to actin filaments
    • piriform cells – underneath umbrella cells and above basal cells, can also adjust morphologically
    • basal cells – located at lowest layer of stratified epith
  • LP = fibroelastic CT, denser near epith –> looser towards muscularis ext, with diffuse lymph tissue = MALT
  • No real muscularis mucosae
transitional epithelium or urothelium and cells of it

transitional epithelium or urothelium and cells of it

Muscularis Ext

  • 3 layers:
    • inner longitudinal layer
    • middle circular layer
    • outer longitudinal – but only in last 1/3 of ureter
  • smooth m responsible for creating peristaltic contractions to convey urine through ureter (30cm)

Adventia

  • 3rd main layer
  • ureter = retroperitoneal, so covered w/ adventia
  • CT + a/v/n
  • adipose

Slide #64 Urinary Bladder * H&E

Contracted Bladder - Our slide doesnt look like this, but this shows layers well

Structures to Identify:

  • urothelium
  • muscularis
  • a/v
  • CT
  • mesothelium
  • PNS ggl

General Info

  • Receives urine from 2 ureters and under appropriate stimulation, will secrete it through urethra
  • lined by urothelium, which allows bladder to adjust to amount of urine

Mucosa

  • Epith = urothelium,  transitional epithelium
    • same cell types as ureter
    • up to 10 layers when bladder empty, # layers dec when bladder is full
  • when bladder is full, cells flatten and appear squamous, & when bladder was empty, cells became dome shaped
  • LP = CT tissue fibers, fibroblasts, a/v, many layers
    • Can either say LP has 2 layers = upper cell rich, and lower fibrous layer
    • Or can say there is a cell rich LP with a fibrous submucosa
    • fibrous layer not present in bladder trigone
  • changes in appearence and cells shapes in transitional epithelium are from thickened regions called plaques
    • interconnected via interplaque regions
    • allow  cell membrane to fold – which disappear when urine flows into bladder

Muscularis Mucosae

  • 3 muscular layers: – inner longitudinal, middle circular, outer longitudinal
  • not as organized as ureter
  • may be ggl cells wich are part of ANS
    • helps regulate urine secretion via relaxation & contraction of muscularis
    • controls detrusor m
  • Internal urethral sphincter = fromed @ site of entry of bladder –> Urethra
  • w/ CT in between, and a/v and capillaries, and occasional n. fibers

Adventia

  • Infraperitoneal
  • fundus covered by peritoneum
  • serosa/ subserosa can be present where peritoneal pres – superiorly –> simple squamous = mesothelial cells
  • SNS n fibers maybe

Beyond the serosa/adventitia covering of the bladder is perivesical fat.  This is a layer of fat surrounding bladder.

Its upside down - sorry

It's upside down - sorry

Slide #71 Penile Urethra * H&E

Structures to Identify:

  • lumen
  • corpus spongiosum
  • smooth m
  • str columnar/ psuedo str columnar
  • tunica albuginea
  • urethral glands of Littre
  • paraurethral ducts
  • endo-epith glands

Mucosa

  • Epith = pseudostratified non keratinized epith
    • epith changes depend on part of urethra
    • Pars prostatica –  urothelium
    • Pars membranous – str columnar
    • Pars spongiosum –  str columnar – until navicular fossa – str squamous
  • LP = thin layer, merges with surrounding corpus spongiosum, cell rich
  • lumen is shaped like ureter, but does NOT have urothelium in our slide, so look for that, and the glands of Littre
  • mucosal folds makes small dips in lumen, and forms lacunae
  • lacunae attached to urethral ducts of urethral glands of Littre
    • mucus secretions
    • thin basophillic (blue) outer layer with pale interior (mucus)
    • duct is more basophillic, with small circular lumen

Corpus spongiosum

  • network  of cavities lined by simple squamous epith
  • a/v in b/w

Outer layer = Tunica albuginea

  • thick eosinophillic layer, with smooth m and elastic fibers
Ducts of Littre

Ducts of Littre

Development of the ureter, urinary vesicle and urethra.

Ureter:

  • intermediate mesoderm forms longitudinal ridge on post body wall = urogenital ridge
  • part of UG ridge becomes nephrogenic cord –> urinary system
  • nephrogenic cord develops into 3 structures: pronephros, mesonephros, metanephros
  • metanephros further develops from ureteric bud and from grouping of mesoderm w/in nephrogenic cord, metanephric mesoderm
  • further development of ureteric bud –> becomes ureters

Urinary bladder:

  • urinary bladder is formed from upper end of urogenital sinus, continuous w/ allantois
  • allantois becomes fibrous cord = urachus * stays in adult as median umbilical lig
  • lower end of mesonephric ducts –> post wall of bladder as trigone
  • mesonephric ducts open into urogenital sinus below bladder
  • transitional epith from endoderm

Urethra:

Female Urethra:

  • female urethra is formed from lower end of urogenital sinus
  • develops as endodermal outgrowths into surrounding mesoderm = urethral glands, paraurethral glands
  • end @ vestibule of vagina, also forms from urogenital sinus
  • vestibule of vagina – develop endoderm growths = greater vestibular glands
  • endoderm = epith

Male Urethra:

  • Prostatic urethra, membranous urethra, prox urethra
    • formed from lower end of urogenital sinus
    • endoderm = transitional epith, str columnar epith
    • prostatic urethra have endoderm outgrowth into mesoderm = prostate gland
    • membranous urethra have endoderm outgrowth into mesodem = bulbourethral glands
    • prox part of penile urethra have endoderm outgrowth into mesoderm = Littre’s glands
  • distal part of penile urethra
    • formed from ingrowth of surface ectoderm = glandular plate
    • glandular plate joins penile urethra and becomes tube = navicular fossa
    • ectodermal septa lat to navicular fossa –> becomes foreskin
    • str sq epith lines part of urethra = ectoderm
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34. The anatomy, histology and development of the testis, epididymis and ductus deferens.

4 Jan

The anatomy, histology and development of the testis, epididymis and ductus deferens.

Anatomy of Testis, Epididymis & Ductus Deferens


Scrotum:
cut pouch of thin pigmented skin and underlying tunica dartos, a facial layer cont w/ superficial penile fascia and superficial perineal fascia

Function:

  • NO fat – to maintain temperature lower than rest of body
  • contains testis and epididymis
  • the dartos m. w/in tunica dartos attaches to the skin – it controls the wrinkling of skin of scrotum

    • contracted and wrinkled when cold (or sexually stimulated), bring testis in close contact w/ body to conserve heat
    • relaxed when warm and hence is flaccid and more pendulous to release and spread heat
    • By transferring the testicles into the scrotum a testicular temperature 2-3 ºC lower than body temperature is attained.  Lower temperature is necessary for producing sperm cells.

Structure

  • divided into R & L compartments via scrotal septum (int) and scrotal raphe (ext)
  • superficial dartos fascia – has no subcutaenous fat, like Scarpa’s fascia of the abdomen

Testis
* considered retroperitoneal

General Info:

  • covered by visceral layer of tunica vaginalis testis – except where in contact w/ epididymis – covered by tunica albuginea
  • attached to scrotum via gubernaculum testis

    • remnant of embryonic caudal ligament
    • responsible for pulling down testis from ab cavity –> scrotum
    • analogous to round ligament in female

Function: produce spermatozoa (spermatogenesis) and secrete sex hormones

Spermatogenesis: production of spermatids, not mature sperm cells yet.  (spermiogenesis covered in next topic, w/ seminal vesicle and prostate)

Anim: http://highered.mcgraw-hill.com/olc/dl/120112/anim0043.swf

  • Spermatogenesis is initiated in the male testis with the beginning of puberty. This comprises the entire development of the spermatogonia (former primordial germ cells) up to sperm cells. The gonadal cords that are solid up till then in the juvenile testis develop a lumen with the start of puberty. They then gradually transform themselves into spermatic canals They are termed convoluted seminiferous tubules (Tubuli seminiferi contorti) . They are coated by a germinal epithelium that exhibits two differing cell populations: some are sustentacular cells (= Sertoli’s cells) and the great majority are the germ cells in various stages of division and differentiation.
  • development of the germ cells begins with the spermatogonia at the periphery of the seminiferous tubule and advances towards the lumen over spermatocytes I (primary spermatocytes), spermatocytes II (secondary spermatocytes), spermatids and finally to mature sperm cells.
  • The Sertoli cell is essential for spermatogenesis as it provides support for the developing sperm cells – moving them towards the lumen of the semiferous tubule as they develop until maturity when they are released. The Sertoli cell also reduces motility and capacitation (initiation of the acrosome reaction) of the sperm cells so viability is maintained.
  • Spermatozoa are produced in seminiferous tubules in the testes. They start off as spermatogonia , undergoing mitosis becoming a type A spermatogonium or a type B spermatogonium.
    • Type B spermatogonia become primary spermatocytes.
    • Primary spermatocytes go through a meiotic division to become secondary spermatocytes, which undergo another meiotic division to become spermatids.
    • Type A spermatogonia stay as spermatogonia, and do not change. They act as stem cells and will divide again producing more Type A and B cells.
  • The primary spermatocytes contain twice the DNA of a normal body cell (2 × 2N).
    • Each primary spermatocyte divides into two secondary spermatocytes containing two sets of chromosomes (2 × 1N).
    • The secondary spermatocytes then divide into two spermatids, each containing just one set of chromosomes (1N), half the DNA needed to make a human being. (The other half will come from the ovum at fertilisation)


Tunica Vaginalis & processes vaginalis testis:

  • fluid filled envelope
  • testis attached to scrotum thru caudal lig of testis  & to peritoneum running above it
  • During descent of testis, pertinoneum is pulled in to scrotal sac w/ testis = processes vaginalis testis –> become tunica vaginalis
  • have a visceral and parietal layer, just like peritoneum


Blood supply:

testicular a (ab aorta)
drained by v of pampiniform plexus –> become testicular v

Lymph vessels in area –> sup inguinal nodes & lumbar nodes

inside-of-testis

Epididymis:

  • formed by the many twists and turns made by the 1 epididymal duct
  • lies of post surface of testis, – only place where testis not covered by tunica vaginalis
  • has head, body, tail

    • head – made up of 12-14 efferent ducts, leading from rete testis
    • body – duct of epididymis
    • tail – continous w/ ductus deferens

Ductus Deferens:

Function:

  • continuation of epididymal duct
  • carries spermatozoa from testis/epididymis to prostatic urethra
  • unites w. duct of seminal vesicle to form ejaculatory duct
  • Terminal portion = ampulla, med to seminal vesicle
  • opens lat to seminal collicus on post wall of prostatic urethra


Pathway/Topography:

  • begins in tail of epididymis –> asc w/ spermatic cord –> inguinal canal –> enter  retroperitoneal space @ deep inguinal ring –> desc to bladder
  • int iliac a (DD runs in front)
  • ureter (DD runs in front)
  • no structure runs b/w peritoneum and DD

Blood supply: deferential a (usually inf vesicle a, sometimes sup vesicle a), joins testicular a w/in scrotum,

Veins = v run w/ a

Lymph Drainage = ext iliac lymph nodes

Nerve supply: inf hypogastric plexus
SNS – causes rapid contracting of musc during ejaculation

Spermatic Cord:

  • develop from genital folds of embryo (analogous to labia majora)
  • L & R  genital folds join to form scrotal raphe in midline of scrotal sac


Pathway:
Deep inguinal ring lat to lat umbilical fold (w/ inf epigastric a/v inside)
–> thru inguinal canal –> exit @ superficial inguinal ring –> scrotum @ post border of testis

Because the testis form in abdominal cavity, and then descends into scrotal sac, the layers of ab wall accompany this trip, and so the same layers can be seen in both spermatic cord, and scrotum

Layers of Ab wall are continuous w/ layer of Spermatic cord:

ab-wall-with-scrotum-layers
Contents of Spermatic cord:
1. Ductus deferens – originates from epididymis & carries spermatozoa

2. Arteries

  1. Testicular a – paired visceral branches of ab aorta w/ pampiniform vein plexus = testis & epididymis
  2. Deferential a (a of ductus deferens) – from inf vesicle artery = ductus deferens itself
  3. Cremasteric a (from inf epigastric a) = cremasteric m


3. Pampiniform plexus – network of v around testicular a and ductus deferens –> ends as testicular v, cools down blood that enters testis

4. Nerves

  • Genital br of genitofemoral n (lumbar plexus) = Cremaster m
  • Autonomic fibers = regulate smooth m of ductus deferens and a/v (VM), and carry VS from testis
    • SNS regulates the a/v, and PNS regulates the DD itself


5. Lymph vessels –> sup inguinal nodes

Blood supply:

  • int pudendal a (int iliac a)
  • Ext pudendal a (femoral a)
  • testicular a (ab aorta)
  • cremasteric a
  • all flow –> testicular v


Innervation:

  • Ilioinguinal n
  • pudendal n
  • perineal br of post cut femoral n
  • genital br of genitofemoral n


Histology of Testis, Epididymis & Ductus Deferens


Slide # 65 Testis & Epididymis

Structures to Identify:

  • Sertoli cells (in semineferous tubules)
  • Leydig cells
  • Tunica Albuginea
  • Epididymis
  • CT septa
  • Ductus Efferents
  • Ductus epidymis
  • Straight Tubules
  • Rete Testis

General Info:

  • covered by thick CT capsule = tunica albuginea
  • just below tunica albuginea, is a layer of a/v =  tunica vaculosa
  • on the posterior side of the testis, the tunica albuginea pushes into the testis to form the mediastiunum testis
  • thin sheets come from the mediastinum testis to form septa between the 250 testicular lobules
  • Each lobule has 1-4 seminiferous tubules, lined by stratified germinal epithelium (same epith like uterus)
    • Epith contains = germ cells, and Sertoli cells
  • Between the seminiferous tubules, are fibroblasts, muscle like cells, a/v/n, and lymphvessels and Leydig cells
  • Leydig cells = produce testosterone

Seminiferous Tubules

  • 1-4 in each lobule
  • triangular nucleus
  • produce spermatids
  • 1st layer = in epith of tubules = Sertoli cells *more later*
  • Contain spermatogenic cells in 2nd layer – b/w sertolis cells and lumen
    • regularly replicating and differentiating
    • organized poorly into layers
  • 3rd layer = Tunica Propria

    • also called peritubular tissue
    • myoid cells sit beneath the basal lamina of Sertoli cells = nursing cells
    • contraction of myoid cells create peristaltic movement
    • if thickens in early life —> Infertility
  • Basal compartment = spermatogonia, primary spermacytes
  • Lumen = mature spermacytes, spermatids
  • surrounded by interstitial tissue

Interstitial Tissue

  • a/v
  • loose CT
  • clusters of epithelial like cells of Leydig
    • eosinophillic, round nucleus
    • lipid droplets
    • crystal of Reifkle = Rectangular, crystal-like inclusions in the interstitial cells of the testis (Leydig cells) and hilus cells in the ovary.
    • elaborate Smooth ER for enzyme production
    • testosterone production
      • in early fetal life = help male gonads develop
      • in Puberty = sperm production, pubic hair growht
      • In Adult = maintenance of sex glands, spermatogenesis

Sertoli Cells = tall columnar, non replicating cells that rest on basal lamina, 5 functions

  1. Supporting cells – processes for exchange of metabolic substances and waste
  2. Phagocytes – junctional complexes, and spermatogonia cells that don’t complete differentiation
  3. Endocrine – Androgen Binding Protein (ABP) – binds testosterone from Leydig cells for proper maturation of spermatozoa, secrete fluid for passing mature sperim
  4. Exocrine – secrete hormones
    • Inhibin – inhibits FSH release
    • Transferrin – Fe transport
    • Plasminogen activators – stimulate proteolytic enzymes
  5. Help form Blood Testis Barrier
    • fluid in seminiferous tubules different from plasma – i.e diff amino acids, ions, carbs
    • protect genetically differentiating cells from immune system
    • junctional barrier
    • The barrier is formed by layers of cells from the VASCULAR ENDOTHELIUM of the capillary BLOOD VESSELS, to the SEMINIFEROUS EPITHELIUM of the seminiferous tubules. TIGHT JUNCTIONS form between adjacent SERTOLI CELLS, as well as between the ENDOTHELIAL CELLS.

Sperm is made and modified through the testicular duct system

Seminiferous tubules (convoluted/straight tubules) -- rete testis (in mediastinum testis) -- Efferent ducts -- Epididymis ducts (tail, body, then head) -- ductus deferens

Pathway: Seminiferous tubules (convoluted/straight tubules) --> rete testis (in mediastinum testis) --> Efferent ducts --> Epididymis ducts (tail, body, then head) --> ductus deferens

Pathway: Seminiferous tubules (convoluted/straight tubules) –> rete testis (in mediastinum testis) –> Efferent ducts –> Epididymis ducts (tail, body, then head) –> ductus deferens

First 4 you can identify in this slide, each one has different epithelial lining and function

Straight tubules: short narrow ducts, with cuboidal lining epith , no spermatogenic cells

Rete Testis: @ mediastinum testis,

  • network of tubules wth wide lumen
  • epith goes from simple squamous to low cuboidal to low columnar.
  • widen near the efferent ducts

Epididymis:

  • include efferent ducts and ducts of epididymis
  • 4-6 M long coiled structure
  • newly produced sperm mature here –> gain motility and ability of fertilize female oocyte
  • head of sperm modified by addition of depcacitation factor, containing  carb like fluid which inhibits a second fertilization of the egg – IMP for transfer of DNA content
  • fluid is released during capacitation in female reproductive tract — IMP for binding to oocyte
  • lined by  pseudo stratified columnar epith, with primary cells and basal cells that have stereociliae
  • lymphocytes are also present
  • resevoir of sperm
  • when stimulated – contraction occurs, ejaculation occurs

Ductus efferentes

notice the star shaped lumen - efferent ducts

notice the star shaped lumen - efferent ducts

  • star shaped lumen –> due to tall ciliated cells, and shorter non ciliated cells
  • found nearer to mediastinum
  • surrounded by CT
  • form part of head of epididymis
  • reabsorb fluid secreted from seminiferous tubules
  • musc layer surrounds ducts to push sperm forward

Ductus epididymis

PRINCIPAL CELLS, are elongated and located at the base.   Another population of cells has a rounder nucleus and can be found mainly at the base (called BASAL CELLS)

Epididymal ducts: PRINCIPAL CELLS, are elongated and located at the base. Another population of cells has a rounder nucleus and can be found mainly at the base (called BASAL CELLS)

  • pseudostratified columnar epith
  • one tube that is convoluted and twisted, so you are seeing mutliple cross sections of its lumen
  • has tall columnar principal cells with non motile stero cilia, and small basal cells (circular and at base)
  • smooth round lumen
  • located towards the outside, away from the medistinum testis

Slide #67 Ductus Deferens in Spermatic Cord


Structures to identify:

  • pseudostratified columnar epith w/ sterocilia
  • all 3 layers of muscle – inner longitudinal, middle circular, outer longitudinal (like in ureter)
  • a/v/n
  • adventia
  • smooth and skeletal m

*Slide easy to identify as you can also see many other structures with it, and also do not confuse with ureter or urethra, this does not have urothelium, and the urethra’s lumen is long, and thin and irregular. This lumen is wide, kinda circular, and irregular.

General Info:

  • tiny narrow irregular lumen, with mucosal foldings into it = glandular diverticuli.
  • thin mucosa – LP has collagen fibers, and elastic fibers
  • THICK muscular layer
  • no submucosa or musc mucosa
  • adventia = no peritoneal relationship

Embryology of Testis, Epididymis & Ductus Deferens

Development of Testis, Epididymis, Ductus Deferens
Until week 6, the embryo does not show a particular gender at all
At week 7 till week 20, embryo under a series of changes until a male or female phenotype is recognized

Gonads become ovaries or, in the case of the male, the testis
The primary genital duct that develops in the male is Mesonephric duct (Think M= male)

Scrotum:
In 3rd week, mesenchyme cells in primitive streak –>go to cloacal membrane to form cloacal folds

  • Cranial (towards the head side, ant) to the cloacal membrane, the cloacal folds form genital tubercle
  • Caudally, cloacal folds become urethral folds ant, and anal folds post

On each side of urethral folds, genital swellings form –> later form scrotal swelling in male, labia majora in female

  • genital swellings grow in inguinal region, move caudally
  • each makes up one half of scrotum, separated by scrotal septum

Testis:

  1. intermediate mesoderm forms longitudinal elevation along dorsal body wall = urogenital ridge
  2. coelemic epith + underlying mesoderm cells proliferate = from gonadal ridge
  3. Primary sex cords from gonadal ridge and absorb primordial germ cells from primitive yolk sac –> later regress, but do form seminiferous tubules, tubuli recti, rete testis
  4. lose connection w/ surface epithelium as tunica albuginea forms there

In order for males to become males, they have a specific gene = TDF, or testis determining factor

Seminiferous cords have the primordial germ cells and Sertoli cells – that secret MIF (Mullerian inhibiting factor), that supresses the development of the primary genital duct in female = the paramesonephric duct or mullerian duct.

Mesoderm b/w seminiferous cords –> give Leydig cells that secrete testosterone
Mesoderm = Leydig, Sertoli cells, primordial germ cells, and CT stroma of testis

Seminiferious cords canalize and form into tubules during puberty


Descent of Testis:

  • All of the above reactions occur w/in the abdominal cavity
  • Testis have to descend into scrotal sac
  • It is unknown what makes them do so – but it seems to be related to growth to ab viscera, the gubernaculum, and testosterone

gubernaculum descends w/ testis in inguinal canal, and remnants of it hold the testis w/in the scrotum in adult life

Peritoneum also follows testis into scrotal sac via inguinal canal, and form the tunica processus vaginalis –> become the parietal and visceral layers of tunica vaginalis

Genital Duct formation:
Paramesonephric duct starts to develop, but later regresses, due to MIF

Mesonephric duct forms = epididymis, ductus deferens, seminal vesicle, ejaculatory duct, efferent ducts of testis

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