Histology notes
Kidney
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functional unit: nephron (1-4 mio)
o cortical nephrons
o juxtamedullary nephrons
nephron consists of:
o renal corpuscle
o prox. Conv. Tubule
o thin & thick limbs of Henle loop
o distal conv. Tubule
o collecting tubules & ducts
renal corpuscle
o glomerolus
 Afferent arteriole
o Bowmans’ capsule
 Parietal layer –simple squamous epithelium
 Visceral layer – Podocytes
o Between parietal & visceral layer: Urinary space
 Vascular & urinary pole
 Podocytes:
 Primary process
 Secondary process filtration slits: 25 mm
Proximal convoluted tubule:
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Simple Cuboidal or low columnar epithelium
Numberous mitochondria
Brush Border
In cross section of tubule
o Only a few cells (3-5)
o No cell boundaries visible – basolateral interdigitations
Henles loop:
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Two types of nephrons:
o Cortical
o Juxtamedullary
General structure:
o Thick descending part
o Thin descending part
o Thin ascending part
o Thick ascending part
o Simple squamous epithelium
Cortical nephron:
o Short thin descending part
o No thin ascending part
Juxtamedullary nephron:
o Short thick descending part
o Long thick ascending &descending part !both!
o Thick ascending part
Distal convoluted tubule:
CELL BORDERS VISIBLE!
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Simple Cuboidal epithelium
No brush border
No apical canaliculi
Smaller cells – more cells seen in cross section
At the vascular pole of nephron:
o Macula densa (tall columnar cells)
 Liberation of:
 1.) Renin
 2.) Angiotensinogen
 3.) Angiotensin I
 4.) Angiotensin II
Collecting tubules & ducts:
Collecting tubules - cuboidal ep. (cortical) - collumnar ep. (medullary)
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Cells stain weaker than usual renal cells
Inter cellular limits clearly visible
Ep. Responsive to Argentine, Vasopressin, ADH
Juxtaglomerular Apparatus:
1) Juxtaglomerular cells
a. Tunica media of afferent arteriole specialized cells
2) Macula densa of distal convoluted tubule
3) Extraglomerular mesangial cells –LACIS cells
Function: Blood pressure regulation due to production of Renin
Bladder & Urinary Passage
Consists of:
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Calyces
Urethers
Urinary Bladder
Urethra
General structure:
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Transtional epithelium (Uroepithelium)
Lamina propria of CT & vessels
Muscle layer
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Circular:
 Calyces
 Renal pelvis
 Urethers
Longitudinal:
 Bladder
Internal longitudinal layer
Middle circular layer
External longitudinal layer
Urethra:
Male:
~ 20 cm
Intramural part
Uroepithelium
Prostatic part
Membranous part
Stratified columnar
epithelium
Spongious part
Fossa navicularis: stratified squamous non
keratinized epithelium
Little glands in the spongious part of the male
urethra are mucous glands
Female:
~ 40 cm
Intramural part: Uroepithelium
Membranous part: Stratified squamous
epithelium
Male Reproductive System:
Seminiferous tubules:
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Spermatozoids are produced in those
Pathway:
o Convoluted seminiferous tubules
o Straight seminiferous tubules
o Rete testis
o Ductuli efferentes
o Epididymic duct
General structure:
o Germinal / seminiferous epithelium
 Sertoli Cells
 Spermatogenic lineage
o Basal lamina
o Fibrous connective tissue
Innermost layer of basal lamina:
o Flattened Myoid cells (smooth muscle characteristics)
Spermatogenesis:
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Process in which Spermatozoids are created
Spermatogonium
Type A Spermatogenia
Stem cells
Type B Spermatogonia
differentiate
Primary Spermatocytes (4n)
Slow
1st meiotic division
Secondary Spermatocytes (2n)
Fast
2nd meiotic division
Spermatids (1n haploid)
Spermiogenesis:
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Process in which Speematids are made into Spermatozoa
Divided into 3 phases:
o Golgi
o Achrosomal
o Maturation
Golgi:
o Proachrosomal granules
o Achrosomal granule
o Achrosomal vesicle
o Centriole movement
Achrosomal:
o Achrosomal vesicle covers anterior half of nucleus: Achrosome
o Forming of:
 Flagellum
 Middle Piece
o Achrosome:
 Hydrolytic enzymes responsible for achrosomal reaction in fertilization &
therefore get access to oocyte
Maturation
o Residual body formation
o Residual cytoplasm is removed by Sertolli cells in late Spermatids
Sertolli Cells:
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Structure:
o Elongated pyramidal cells
o Bases lie on basal lamina
o Apical ends extend into lumen of seminiferous tubules
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Adjacent Sertolli cells connected by:
 Tight junctions (Blood testis barrier)
 Gap junctions (cycle of seminiferous epithelium)
Function:
o Support of Spermatozoa (nutrients)
o Maturation phase of Spermiogenesis
o Secretion of:
 ABP (androgen binding protein)
 Inhibin
o Production of:
 Anti-Müllerian-hormone (AMH)
o Inhibit Z (growth factor B family
o BLOOD-TESTIS-BARRIER
Leydig cells:
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steroid secreting cells:
o Testosterone
o Dihydrotestosterone
Factors influencing testicular function:
Hypothalamus
FSH/ CH-RH
Inhibin (-) Activin (+)
Negative feedback of Androgen
Ant. Pituitary gland
LH +
Leedig Cells
Testosterone (Androgen)
Blood vessel
FSH +
Sertolli Cells
ABP in
seminiferous tubule
Intratesticular genital ducts:
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Composed of:
o Tubuli recti
o Rete testis
o Ductuli efferentes
Tubuli recti:
o Loss of spermatogenic cells
o Cuboidal epithelium
Rete testis:
o Thickening of tunica albuginea
o Cuboidal epithelium
Ductuli efferentes:
o 10 – 20 only
o Ciliated & uncillated cuboidal epithelium
Excretory genital ducts:
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Composed of:
o Ductus Epididymis
o Vas deferens
o Urethra
Ductus Epididymis:
o Pseudostratified columnar epithelium with stereocilia
o Basal lamina
o Smooth muscle cells
Ductus deferens :
o Pseudostratified columnar epithelium with stereocilia
o Lamina propria
o Muscular layer:
 Inner longitudinal
 Middle circular
 Outer longitudinal
Accessory genital glands:
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Composed of:
o Seminal vesicle
o Prostate
o Bulbourethral glands
Seminal vesicles:
o Pseudostratified columnar epithelium
o Highly tortuous glands / tubes
o Produces yellowish fluid: high in fructose
Prostate:
o Tubuloalveolar glands
o Ducts empty into urethra at colliculus seminalis
o Has 3 zones & 3 gland types
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Penis
Pseudostratified columnar epithelium
Bulbourethral glands
o Proximal to membranous part of urethra
o Tubuloalveolar glands
o Simple cuboidal epithelium