Download Seminiferous tubule

Histology of the
male reproductive system
Testis (gonad)
Spermatogenesis
Testosterone
Ducts
Epididymis
Ductus deferens
Urethra
Glands
Seminal vesicle
Prostate
Bulbourethral glands
Penis
Testis
Structure of the testis
Stroma
Tunica albuginea
Septa separate lobules
Mediastinum
Seminiferous tubules
Hairpin-shaped; 30-70 cm each;
250 M total/testis
Convoluted portion seminiferous
epithelium
Straight portion (tubuli recti)
Mediastinum
Septa
Tunica
albuginea
Structure of the testis
Stroma
Tunica albuginea
Septa separate lobules
Mediastinum
Seminiferous tubules
Hairpin-shaped; 30-70 cm each;
250 M total/testis
Convoluted portion seminiferous
epithelium
Straight portion (tubuli recti)
Straight
portion
Rete
testis
Convoluted
portion
Endocrine testis
Interstitial
cells
Interstitial cells (of Leydig)
Clusters in CT between tubules
Steroid secreting cytology
Secrete testosterone,
regulated by interstitia
cell stimulating hormone
(ICSH); male homolog
of LH
Seminiferous
tubule
Seminiferous tubules
Tunica albuginea
Seminiferous
epithelium
Seminiferous tubules
Convoluted portions lined by the seminiferous epithelium
Germ cells (spermatogenic cells)
Sertoli cells (supporting cells)
Sertoli cells
Columnar cells extend to the lumen
Nucleus - euchromatic, ovoid and
infolded; its long axis usually lies
perpendicular to the basal lamina
Numerous lateral processes
surround and invest maturing
germ cells
Sertoli cells
Functions regulated by (FSH)
Regulate germ cell movement and
nutrition
Secrete androgen binding protein
(ABP) to increase local
concentration testosterone
Form blood-testis barrier
Blood-testis barrier
Formed by occluding junctions between
lateral processes of adjacent Sertoli
cells
Basal compartment
Contains early developing germ cells
Compartment similar to tissue fluid
Adluminal compartment
Contains later developing germ cells
Unique microenvironment
Antigenic isolation for germ cells
High testosterone concentration
Spermatogenesis
74 day process
Diploid spermatogonia
become haploid spermatozoa
Spermatozoa
Occurs only the convoluted
portions of the seminiferous
tubules
Regulated by FSH and
testosterone
Spermatogonium
The germ cells – spermatogenic cells
Spermatozoa (SP)
(free in the lumen)
Spermatids (ST)
Secondary
spermatocytes (S)
Primary
spermatocytes (P)
Spermatogonia (SG)
Meiosis
1.
Cell division process restricted to the germinal cells in the
gonads (ovary and testis) for the production of gametes
(ovum and sperm).
2.
Results in reduction of the chromosome number by one-half
(haploid). Fusion of the gametes to form a zygote
reconstitutes the normal diploid number of chromosomes
present in somatic cells.
3.
Results in four daughter cells
4.
Meiosis occurs in two stages, Meiosis I and Meiosis II
Meiosis I – Reductional division
Meiosis II – Equational division
Spermatogenesis
Spermatogonium
Primary
spermatocyte
Reductional
division
Equational division
Secondary
spermatocytes
Spermatids
Spermatozoa
Primary spermatocytes contain 23 paired, replicated chromosomes (chromatids)
Primary spermatocytes divide by Meiosis I which segregates one member of each
pair to the daughter cells (secondary spermatocytes), thereby reducing
chromosome number from 2N to 1N (haploid) (reductional division)
Secondary spermatocytes divide by Meiosis II (equational division) which
segregates one chromatid of each replicated chromosome to the daughter
cells (spermatids)
Spermatogonia
Self-regenerating, diploid stem cells
Located in the basal compartment; divide by mitosis
Self-regenerating population; some become primary spermatocytes
Karyokinesis but no cytokinesis
Spermatogonium
Spermatogonium
Primary spermatocytes
Pass through the
blood testis barrier
into the adluminal
compartment
Begin meiosis I but
arrest in prophase
Diploid
Divide by meiosis I
(reductional division)
Nucleus is 1.5x that of
spermatogonium
nucleus
Secondary spermatocytes
Formed by completion
of meiosis I by primary
spermatocytes
Haploid
Present for only 8 hours
Divide by meiosis II
(equational division)
Nucleus is about equal
size as spermatogonium
nucleus
Spermatids
(early)
Formed by completion
of meiosis II by
secondary spermatocytes
Haploid
Do not divide, undergo
cytodifferentiation
(spermiogenesis)
Nucleus is 2/3 the size of
spermatogonium nucleus
Spermatids
(late)
Continue differentiation to
form spermatozoa
Intercellular bridges break
down
Nucleus condenses and
elongates, acrosome forms
Flagellum forms
Excess cytoplasm is shed
Released from Sertoli cell
(spermiation)
Spermiogenesis
Early spermatid
Late spermatid
Spermatozoan
Zona
pellucida
Oocyte
Spermatogenesis
Mitosis
(Spermatocytogenesis)
Meiosis
Diploid
Haploid
Cytodifferentiation
(Spermiogenesis)
Release (Spermiation)
Capacitation = Final maturation of sperm, in the female tract
Course of sperm within testis
Seminiferous tubules, convoluted portion:
Seminiferous tubules, straight portion (tubuli recti)
Rete testis - Meshwork of channels within the mediastinum
Straight
portion
Convoluted
Rete
testis
Convoluted
portion
Convoluted
portions
Mediastinum
with
rete testis
Rete
testis
Tubuli
recti
Efferent ducts
Connect with rete testis and emerge from
the superior end of the testis
Become highly coiled, conical structures
(conus vasculosus)
Simple epithelium composed of tall,
ciliated cells and short cuboidal cells
Propel spermatozoa and resorb testicular
fluid
Terminate in the head of the epididymis
Head of the Epididymis
Bases of the coni vasculosi
Duct of the epididymis
Conus vasculosus
Conus
vasculosus
Duct of epididymis
Epididymis
Subdivisions:
Head, body and tail
Functions:
Storage and maturation site for sperm
Absorption of excess testicular fluid
Movement of sperm toward ductus deferens
Duct of the epididymis
Spermatozoa
Pseudostratified epithelium with stereocilia
Highly coiled tube, 4-6 meters in length
Ductus deferens
Muscular tube carrying sperm from duct of
epididymis to the ejaculatory duct in the prostate
Pseudostratified columnar epithelium with stereocilia
Thick muscularis externa - inner and outer longitudinal,
middle circular layers of smooth muscle
Spermatic cord
Ductus deferens
Spermatic artery
Pampiniform plexus of veins
Cremaster muscle
Nerve plexus
Pampiniform
plexus
Spermatic
artery
Ductus
deferens
Ductus deferens
Enters abdominal cavity, crosses above entrance of ureter into bladder,
and enlarges to form the ampulla
Joined by duct of the seminal vesicle just before entering prostate and
forming the ejaculatory duct in the prostate
Ejaculatory duct joins the prostatic urethra
Ductus deferens
Seminal vesicle
Ejaculatory duct
Prostate
Prostatic urethra
Epididymis
Penile urethra
GENITAL GLANDS
Bladder
Seminal vesicles
Prostate gland
Seminal
vesicle
Bulbourethral glands
Prostate
Bulbourethral
Posterior view
Seminal vesicles
Paired glands, each a single, highly folded tube
Complex mucosal folds create appearance of
irregular chambers in the lumen
Pseudostratified columnar epithelium
Secretions: Provides bulk of seminal fluid;
fructose, citrate, proteins, prostaglandins;
sperm coagulating factors
Prostate
Surrounds the confluence of the ejaculatory duct and urethra
Ductus deferens
Seminal vesicle
Ejaculatory duct
Prostate
Prostatic urethra
Epididymis
Penile urethra
Prostate
30-50 tubulo-acinar glands
Glands lined with pseudostratified columnar epithelium
Prostatic concretions, increase with age
Secretion: Citric acid,
Acid phosphatase
Prostate specific antigen (PSA) (serine protease)
Fibinolysin
Arrangement of prostatic glands
Central (periurethral) zone
Transitional zone
Peripheral zone (70% of total gland)
Benign prostatic (nodular) hyperplasia (BPH) - growth of
glands and stroma in central and transitional zone
Majority of prostate cancers develop from the peripheral
zone
Peripheral zone
Transition zone
Central zone
Penis
Outer covering of thin skin
CC
Tunica albuginea:
CC
Dense, non-elastic CT surrounding cylinders of
erectile tissue
Erectile tissue:
Spongy tissues composed of cavernous venous
spaces
Corpora cavernosa (CC) - paired dorsal cylinders
Corpus spongiosum (CS) - single, ventral cylinder,
houses the penile urethra
Corpora cavernosa contain the deep artery of the
penis and helicine arteries which deliver blood
during erection
CS
Erection
Parasympathetic smooth muscle relaxation
Dilation of the deep and helicine arteries
Cavernous spaces fill with blood
Sympathetic activity and reduced parasympathetic activity
terminate erection
Cavernous
spaces
Penile urethra
Located within corpus spongiosum
Pseudostratified columnar epithelium becomes
stratified squamous moist at its opening
Glands of Littre - Secrete a mucous fluid that is
part of the initial ejaculate; provides
lubrication
Penile urethra
Penile
urethra
Corpus
spongiosum
Glands of
Littre