UGS Lecture – 6(2021)

Mons Pubis● Rounded eminence found, in both sex

anterior to pubic symphysis, pubic tubercle,and superior pubic rami.

● Formed by a collection of subcutaneousadipose connective tissue.

● After puberty mons pubis becomes coveredwith coarse hair and amount of fat increases.

● The pubic hair in male extends upward toumbilicus.

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The Male Mons Pubis

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Mons pubis showing thefemale distribution of

pubic hair

Mons pubis showing thefemale distribution of

pubic hair

The Female Mons Pubis

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Penis● It is composed of three cylindrical column

of erectile cavernous tissue: the pairedcorpora cavernosa, dorsally placed and thesingle corpus spongiosum in middle,ventral to them.

● The three cylindrical masses of erectiletissue are enclosed within, and separatedby a dense connective tissue, tunicaalbuginea.

● Superficial to tunica albuginea is deepfascia of penis, Buck fascia, which containsprominent blood vessels.

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● The corpus spongiosum contains penileurethra.

● The corpora cavernosa are closed to eachother except proximally where they divergeto form crura of penis.

The penis has a fixed part termed root, and afree pendulous part known as body.A. Root: Lies in superficial perineal pouch.B. Body:● Is the free part that is suspended from

pubic symphysis.5

● The corpora cavernosa form greater part ofbody, and are placed in dorsal part.

● Proximally, each is continuous withcorresponding crus of penis.

● The corpus spongiosum lies in middleventral to corpora cavernosa.

● Proximally, it is continuous with bulb ofpenis.

● Distally, it expands in front of corporacavernosa forming glans penis (head ofpenis). 6

● The margin of glans projects beyond end ofcorpora cavernosa to form corona of gland.

● The corona overhangs the neck of glans.

● Neck separates the glans from body of penis.

● The penile urethra traverses bulb of penis andcorpus spongiosum and opens on tip of glanspenis forming external urethral meatus, whichis a slit-like orifice.

● The thin skin and fascia of the penis areprolonged as a hood like double layer (fold) ofskin, the prepuce (foreskin) that covers glansto a variable extent. 7

bulb ofpenis

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The Penis – Longitudinal Section

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The Penis – Cross Section

● It is connected to glans penis just belowexternal urethral meatus by a median foldknown as frenulum of penis.

The body of penis is supported by twocondensations of deep fascia:

(1) Fundiform ligament of penis:● Descends in midline from linea alba just

above pubic symphysis.

● Inferiorly, it splits to surround penis andthen unite to form scrotal septum.

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(2) Suspensory ligament of penis: Descendsfrom anterior surface of pubic symphysisand splits to form a sling that is attached todeep fascia of penis at junction of its rootand body.

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Fundiform ligament ofpenis

Suspensoryligament

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Ligament that support the penis

Blood Supply of PenisThe internal pudendal artery gives off thefollowing branches:a. Artery of bulb: Supplies the corpus

spongiosum.

b. Deep arteries of penis: Supply corporacavernosa.

c. Dorsal arteries of penis: Supply remainingareas of penis.

Veins from penis drain into internalpudendal veins. 13

Accessory Genital GlandsA. Seminal Vesicles:● The seminal vesicles are two symmetrical

lobulated organs situated obliquely onposterior surface of bladder.

● Each seminal vesicle is about 5 cm longextends from the termination of ureter tobase of prostate.

● It is related posteriorly to rectum, fromwhich it is separated by rectovesical fascia,and medially to vas deferens.

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● The vertical axis of each seminal vesicle isdirected downwards and medially, so thattheir lower ends are closer than upper.

● The inferior end of each seminal vesiclejoins vas deferens of same side to formejaculatory duct.

● The seminal vesicles secrete up to 85% oftotal volume of seminal fluid, most of restbeing secreted by prostate.

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SeminalvesicleSeminal vesicle

ductEjaculatoryduct

16The Seminal Vesicles

B. Prostate:● It is a walnut size gland that surrounds

prostatic part of urethra.

● The organ is enclosed by a dense fibrouscapsule that incorporates prostatic plexus ofnerves and veins.

● The capsule is surrounded by visceral layerof pelvic fascia, which is continuousanterolaterally with puboprostatic ligaments,and posteriorly with rectovescical septum.

● It is somewhat conical in shape, consists ofan apex, a base, and four surfaces: anterior,posterior, and two inferolateral. 17

● The anterior muscular surface is connectedto pubic bone by the puboprostaticligaments.

● It is separated from pubis symphysis byretropubic pad of fat in retropubic space.

● The posterior surface is separated fromampula of rectum by rectovesical septum.

● At upper border of this surface, the twoejaculatory ducts enter prostate.

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● Each inferolateral surface is clasped by theanterior fibers of the corresponding levatorani muscle (levator prostate), which forminga sling around prostate.

● The base of the gland being applied to neckof bladder and is perforated near its centerby urethra.

● The urethra traversed gland from base toapex.

● The apex (inferior aspect) lies againstsuperior aspect of sphincter urethrae anddeep transverse perineal muscles (urogenitaldiaphragm). 19

ProstateProstati

curethra

External urethralsphincter

20The Prostate Gland

Retropubic padof fat Prostat

eProstaticurethra

Ejaculatoryduct

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The Prostate Gland

The prostate is completely divided into fivelobes:

a. Anterior lobe (Isthmus):● Lies in front of urethra.

● It is primarily muscular and representssuperior continuation of urethral sphinctermuscle.

● It contains no glandular tissue.

b. Middle lobe: Lies behind urethra andabove ejaculatory duct. 22

C. Posterior lobe:Lies behind urethra and below ejaculatoryduct.

d. Right and left lateral lobes:● Lie on either side of urethra.

● They form major part of prostate.23

Middlelobe

Anteriorlobe

Posteriorlobe

24 Prostatic Lobes

Blood Supply of the ProstateThe prostate is supplied by inferior vesical,middle rectal and internal pudendal arteries.

Veins form plexus within the capsule calledthe prostatic venous plexus, which drainsinto internal iliac veins.

Lymph Drainage of the Prostate● Lymph vessels from prostate end in

internal iliac and sacral lymph nodes.● Few vessels however drain into external

iliac lymph nodes.25

C. Bulbourethral Glands or Cowper’s Glands:● Are two pea-size glands that lie

posterolateral to membranous part ofurethra, largely embedded within externalurethral sphincter.

● Their ducts pierce perineal membrane andopen on posterior wall of penile urethra inbulb of penis.

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Bulbourethral Glands 27

Bulbourethralglands

Histology of the MaleReproductive System

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Testes● The spaces between adjacent seminiferous

tubules are filled with connective tissue, bloodcapillaries, extensive network of lymphaticvessels, and nerves. The connective tissuecontains various cell types, includingfibroblasts, undifferentiated connective cells,mast cells, and macrophages.

● During puberty, an additional cell typebecomes apparent, which is either rounded orpolygonal in shape, and has a central nucleusand an eosinophilic cytoplasm rich in smalllipid droplet. These cells are called theinterstitial (leydig) cells. 29

● The seminiferous tubules produce, spermatozoa,whereas leydig cells secrete testosterone.

● The seminiferous tubules are coiled, about 30 –70 cm long.

● Each tubule has the following walls:

a. Tunica propria:● It is a fibrous connective tissue enveloping

seminiferous tubules, composed of several layersof fibroblasts.

● The most inner layer adherent to basal laminaconsists of flattened myoid cells, which have thecharacteristics of smooth muscle. 30

Low power of a section through theseminiferous tubules. Note the spacesbetween the tubules are filled withconnective tissue containing lydig cells

b. Seminiferous (germinal) epithelium:● Composed of two types of cells: sertoli or

sustentacular cells, and spermatogeniccells (spermatogenic lineage).

● The latter are stacked in 4 – 8 layers,consists of the following types of cells:

spermatogonium, primary spermatocytes,secondary spermatocytes, and spermatids.

● Their function is to produce spermatozoa.The seminiferous epithelium rests on a well-defined basal lamina.32

Latespermati

cs

Earlyspermatid

s Secondary

spermatocytes

Primaryspermatocyt

es

spermatogonia

Seminiferous (germinal) epithelium 33

Spermatogenesis● Spermatogenesis is the process by which

spermatids are formed.

● Sperm production begins at periphery ofseminiferous tubules in primitive germ cellscalled spermatogonium, which are situatednext to the basal lamina of epithelium.

● These cells begin dividing by mitosis,producing successive generations of cells.

● The newly formed cells can follow one oftwo paths: 34

(1) they can continue dividing as stem cellscalled spermatogonia type A, or,

(2) they can differentiate during progressivemitotic division to form spermatogonia typeB.

● Spermatogonia type A, characterized by alarge round or oval nucleus withcondensed chromatin; peripheral nucleoliand a nuclear vacuole may be prominent.

● Spermatogonia type B have dispersedchromatin, central nucleoli, and no nuclearvacuole. 35

● Spermatogonia type B undergo furthermitotic divisions to produce primaryspermatocytes, which have 46 (44 + XY)chromosomes.

● These migrate towards the lumen ofseminiferous tubule.

● Soon after their formation, the primaryspermatocytes enter the prophase of thefirst meiotic division, which takes about 22days.

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● The primary spermatocytes are the largestcells of spermatogenic lineage and arecharacterized by presence of chromosomesin various stages of coiling within theirnuclei.

● From first meiotic division arise smaller cellscalled secondary spermatocytes, which have23 chromosomes (22 + X or 22 + Y).

● The smaller secondary spermatocytesrapidly undergo second meiotic division toform spermatids and are therefore seldomseen.

● Each secondary spermatocyte divides intotwo spermatids that contain 23chromosomes. 37

Primaryspermatocyt

es Late

spermatics

Spermatogonia

Sertoli cells

High power of section through asemineferous tube showing the various celltypes. 38

High power of section through a semineferoustube. Note the extent of the sertoli cell. 39

Latespermati

cs

Earlyspermati

cs

Primaryspermatocyt

es

Sertoli cells

Spermatogonia

Spermiogenesis● Is process by which spermatids are

transformed into motile mature spermatozoa.

● It involves the following major stages:(1) The Golgi complex elaborates a large

vesicle, acrosomal vesicle, whichaccumulates carbohydrates and hydrolyticenzymes.

(2) The acrosomal vesicle spreads to coveranterior half of progressively elongating andcondensing nucleus to form acrosomal headcap. 40

(3) Meanwhile, both centrioles migrate to endof cell opposite to acrosomal head cap. Oneof the centrioles elongates to form aflagellum.

(4) The cytoplasm migrates to surround theproximal part of flagellum forming athickened region known as middle piece.Mitochondria aggregate around flagellum inthis region.

(5) As the flagellum elongates, excesscytoplasm is shed and phagocytosed bySertoli cell prior to release of sperm intolumen. 41

Spermiogenesis 42

Acrosomalgranule

Golgi

Mitochondrion

Centrioles

Acrosomalvesicle

Nucleus

Flagellum

A B

Acrosomal cap Acrosome

Middle piece

Residual bodies

AcrosomeMitochondria

C D

Spermiogenesis

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Sertoli cells● Are large cells, which extend from

basement membrane to lumen of tubule.

● They are elongated pyramidal cells havingan extensive cytoplasm that envelop cellsof spermatogenic lineage.

● In light microscope, their outline appearpoorly defined because of the numerouslateral processes that surroundspermatogenic cells.

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● Studies with electron microscope revealthat these cells contain abundant smoothendoplasmic reticulum, a small amount ofrough endoplasmic reticulum, a welldevelop Golgi complex, and a moderatenumber of mitochondria.

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Functions of Sertoli cells:• (1) Support and protect developing

spermatogenic cells: Sertoli cells providesupport and protection to developingspermatogenic cells in several ways. Theynourish spermatocytes, spermatids, andsperm; and control movements ofspermatogenic cells and release of sperminto lumen of seminiferous tubule.

• (2) Produce blood-testis barrier: AdjacentSertoli cells are bound together byoccluding junctions at basolateral part ofthe cell, forming a blood-testis barrier.

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▪ (3) Phagocytoses: They phagocytizeexcess spermatid cytoplasm, which shedas residual bodies during spermiogenesis.

▪ (4) Secretion of factors that regulatespermatogenesis and spermiogenesis.

▪ (5) Secretion of factors that regulate thefunction of lydig cells.

▪ (6) Secretion of inhibin, which suppressessynthesis and release of FSH in theanterior pituitary gland.

▪ (7) Secretion of tubular fluid, which is usedfor sperm transport.

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