Urinary Histo

Front 1

Kidney

Back 1

Functions include: production of urine, regulation of fluid and electrolyte balance of the body, production of renin and erythropoietin
 Divided into two parts:
o Outer cortex (renal corpuscle, proximal convoluted tubule, distal convoluted tubule)
o Inner medulla (loop of Henle, collecting ducts and tubules)
 Area between the cortex

Front 2

uriniferous tubules

Back 2

Uriniferous tubules:
1. Nephron
2. Collecting Ducts/Tubules

Front 3

nephron

Back 3

Functional unit of the kidney
 Secretory part of kidney concerned with urine formation
 1-4M nephrons per kindey
 Participate in filtration, absorption, and secretion

Front 4

juxtamedullary nephrons

Back 4

 Only 1/7 of nephrons
 Located near the corticomedullary junction
 Very long Loop of Henle, particularly long thin descending and ascending limbs that extend into medulla
 Essential in establishing gradient of hypertonicity in medullary interstitum to produce hypertonic urine

Front 5

cortical nephrons

Back 5

More numerous, 6/7 of nephrons
 Located mainly in the cortex
 Loop of Henle is short, with very short thin descending and short/no thin ascending limbs
 Reabsorbs water

Front 6

parietal layer bowman's/glomerular capsule

Back 6

Parietal layer (external)
- Form the outer limit of renal corpuscle
- Lined by simple squamous epithelium
- Suppoted by basal lamina with reticular fibers
- Urinary pole:

Front 7

urinary pole

Back 7

a “break” in the parietal layer that becomes continuous to form the proximal convoluted tubule; lined by simple cuboidal or low columnar epithelium
b. Visceral layer (internal)

Front 8

bowmans/glomerular capsule

Back 8

Double-walled epithelial capsule

Front 9

glomerulus

Back 9

tuft of capsules

Front 10

visceral layer bowman's capsule

Back 10

Envelops glomerulus and comes in contact with glomerular capillaries
- Greatly modified
- Can only be seen through EM
- With podocytes which have cell bodies from which arise the:
 Primary processes/foot processes that form finger-like extensions called secondary processes/ pedicels which will interdigitate with one another to form elongated spaces filtration slits/slit diaphragm (25nm)

Front 11

glomerular basement membrane

Back 11

Between capillary endothelial cells and pedicels
- Serves as filtration barrier that separates the urinary space from blood in glomerular capillaries

Front 12

lamina densa

Back 12

hysical barrier that will not allow particles greater than 10nm in diameter to pass through the basal lamina.

Front 13

lamina rara

Back 13

negatively charged thus, will repel negatively charged particles like proteins except those particles with size <albumin.
 The GBM contains anionic sides. It also

Front 14

GBM membrane layers

Back 14

Fenestrated epithelium
 Basal lamina
 Slit pore between podocytes of visceral epithelium and anionic sides

Front 15

bowman's space

Back 15

urinary space
Space between the two layers of the Bowman’s capsule
- Receives fluid through the capillary wall and the visceral layer (glomerular filtrate)

Front 16

vascular pole

Back 16

Where afferent arteriole enters and where efferent arteriole leaves
- Where parietal and visceral layers will meet

Front 17

urinary pole

Back 17

Beginning of proximal convoluted tubule
- Diametrically across the vascular pole
- Portion where in the parietal layer becomes continuous with the proximal

Front 18

mesangial cells

Back 18

Structural supporting cells found in between capillaries in glomerulus
 2-3 mesangial cells per capillary
 Helps in the formation of extracellular matrix
 Can cause vasoconstriction  Acts as macrophage that endocytosse normal or pathologic molecules that are trapped within the glomerular membrane
 Produce chemical mediator such as cytokines and prostaglandins
 In Glomerular Nephritis, there is an increased mesangial hypercellularity

Front 19

if stimulate these substances in mesangial cells, cause vasoconstriction

Back 19

o Contractile cells with receptors for Angiotensin II which is a potent vasoconstrictor that reduces glomerular flow
o Receptors for natriuretic factor (NF, vasodilator from atrial cells); if stimulated, mesangial cells will help vassodilate the capillaries thus, favoring blood flow and increasing glomerular filtration
 Acts as macrophage that endocytosse normal or pathologic

Front 20

proximal convoluted tubule

Back 20

Found only in cortex
 Reabsorbs 60-65% water and solutes
 Also absorbs glucose, amino acids
 Reabsorbs 85% Na
 Most tortuous and the longest part of nephron
 See near renal corpuscle (acidophilic)
 Lined by simple cuboidal epithelium with brush border composed of microvilli that increases surface are for absorption
 Excretes creatinine which is a metabolic waste product
 Involved in vitamin D hydroxylation
 Intercellular junctions are not clearly demarcated
 With 2 parts; Pars convolute and Pars recta

Front 21

loop of henle and parts-epi

Back 21

U-shaped structure; more in medulla than cortex
 With 4 parts:
o Thick descending – Simple cuboidal epithelium
o Thin descending – Simple squamous epithelium with irregulary spaced microvilli
o Thin ascending – Simple squamous epithelium
o Thick ascending – Simple cuboidal epithelium

Front 22

functions loop henle

Back 22

Thin descending – May reabsorb water (5%) that will go to medullary interstitium; but does not permit absorption of Na
o Thick limbs – Transports NaCl out of the tubule
o Thick ascending and thin ascending – Reabsorbs Na but is impermeable to water
Note:
 There is countercurrent mechanism

Front 23

countercurrent mechanism in limbs

Back 23

increases Na+ in the medullary interstitium thus causing hypertonicity and increase in osmolarity.
 Reabsorb water will go to vasa recta causing countercurrent multiplier effect. (the difference between vasa recta and thin limbs in histological preparation is that vasa recta contains RBC). Vasa recta is lined by simple squamous epithelium.

Front 24

distal convoluted tubule

Back 24

Once thick ascending limb penetrates th cortex
 Located in cortical area
 Lined by simple cuboidal epithelium with no brush border
 Absorbs Na and water
 Secretes K in the presence of aldosterone
 Secrete H and ammonium ions (participates in making urine acidic or alkaline and in acid-base balance)
 More basophilic and contains more nuclei
 Lumen is larger
 Intercellular junctions can be appreciated

Front 25

macula dense

Back 25

When DCT approaches the vascular pole, it can undergo multiplication and modification making its cells more columnar and having more nuclei that are closely packed together
 Found near renal corpuscle
 Modified segment of wall of DCT near vascular pole
 Functions to regulate rate of filtration
 Also sensitive to Na+

Front 26

JG cells

Back 26

Modified smooth muscle cells of the tunica media of the afferent arteriole
 Contains more nuclei and numerous Golgi complexes
 Found in the vascular pole
 Produces renin (protease)

Front 27

effects of Renin

Back 27

o Converts Angiotensinogen to Angiotensin I (inactive form)
o Through the action of Angiotensin Converting Enzyme (ACE, from endothelial cells of lungs), Angiotensin I is converted into Angiotensin II
o Angiotensin II is a potent vasoconstrictor that is important in maintaining BP and in stimulating

Front 28

aldosterone effect dct

Back 28

will act on DCT to increase Na and Cl reabsorption and absorption of water causing fluid retention and increase in BP.
 Compensatory mechanism activ

Front 29

juxtaglomerular apparatus

Back 29

Macula densa of DCT
 JG cells of afferent arteriole
 Extraglomerular mesangial cells (Lacis) between efferent and afferent arteriole (they are sensitive to changes that will stimulate macula densa)

Front 30

collecting tubules

Back 30

Found in cortex and medulla (receives urine from DCT)
o Medullary ray: projections in the base of renal medulla; collecting tubules and straight portions (thick) loop of Henle
o Medullary pyramid: collecting tubules/ducts and loop of Henle
 Tubules join one another to form collecting ducts that will increase in diameter once near the renal papilla to become low columnar cells (Collecting ducts or Papillary duct of Bellini)
 Lined by simple cuboidal epithelium that becomes low columnar deep in the medulla
o Principal cells, intercalated cells

Front 31

principal cells

Back 31

mediates the collecting duct’s influence on sodium and potassium balance via sodium channels and potassium channels located on the cell’s apical membrane. Aldosterone and vasopressin let the principal cells control the quantity of water which is reabsorbed.

Front 32

intercalated cells

Back 32

come in α and β varieties and participate in acid-base homeostasis
 α- intercalated cells secrete acid (via an apical H-ATPase and H/K exchanger) in the form of hydrogen ions
 β- intercalated cells secrete bicarbonate (via pendrin, a specialized apical Cl-/HCO3-)
Carry out final mechanism of urine concentration system
 Epithelium is responsive to arginine vasopressin or ADH secreted by posterior pituitary duct; function is to increase permeability of collecting ducts so that it will reabsorb water and decrease secretion of water in the urine
 With aquaporins: sensitive for reabsoprtion of water

Front 33

calyces

Back 33

Once glomerular filtrate enters the calyces (already formed urine)
 Mucosa: transitional epithelium and supported by lamina propria of loose dense CT
 Dense woven sheath of smooth muscle
 Serosa: covered by peritoneum

Front 34

ureter

Back 34

Stellate shaped lumen
 Muscular layer:
o Upper: Inner longitudinal and outer circular muscle fibers
o Lower: Inner longitudinal, middle circular, and outer longitudinal muscle fibers
o Intravesicular: Longitudinal muscle

Front 35

urinary bladder

Back 35

Transitional epithelium varies
 Empty bladder: Epithelium is made up of 6-8 cells thick
 Full bladder: Stretched, 3-4 cells in thickness
 Smooth muscle: Detrusor muscle (3 poorly delineated muscle: inner and outer longitudinal, middle circular)
 Histologically, empty bladder is thrown into folds.

Front 36

female urethra

Back 36

Stratified squamous, non-keratinizing and areas of pseudostratified columnar epithelium
 Below bladder neck: Involuntary internal urethral sphincter
 Above the urogenital diaphragm: Voluntary external striated sphincter
 Histologically: looks like vagina

Front 37

male urethra

Back 37

Preprostatic/prostatic: Transitional epithelium (near the urinary bladder)
 Membranous: Pseudostratified or stratified columnar; sphincter or striated muscle (external sphincter)
 Spongy/cavernous: Stratified columnar with stratified squamous non-keratinizing (near skin); enclosed with erectile tissue of penis
 Littre’sglands: Urethral glands that is more numerous in spongy part
 Surrounded by corpus spongiosum

Front 38

embryo urinary sys

Back 38

Part of the urogenital system, also related to the genital system
 From intermediate mesoderm
 Three overlapping kidney systems are formed in a cranial to caudal sequence: pronephros, mesonephros, and metanephros

Front 39

pronephros

Back 39

Appear at 4th week of fetal life, represented by few tortuous cells and a cluster of cells in the neck; 7 to 10 solid cell groups in the cervical region
 At the end of the 4th week, disappear and form vestigial excretory units (rudimentary and non-functional)

Front 40

mesonephros

Back 40

Appear late in the 4th week
 Formation of excretory tubules
 Large elongated excretory organs; during regression of pronephros, first excretory tubules of mesonephros are formed cephalically forming an S-loop and obtain a bunch of capillaries which will eventually form the glomerulus (around this, Bowman’s capsule will form and all together these structures constitute the renal corpuscle) and then continue caudally to connect with the mesonephric duct/ Wolffian duct
 Usually in females, there will be complete regression of mesonephros
 In males, some tubules will contribute to the formation of male genital system
 The mesonephric ducts induce the formation of the paramesonephric/

Front 41

metanephros

Back 41

5th – 6th week of fetal life, functions at 10th week
 Urine production at 9th week
 Definitive, permanent kidney
 Initially positioned in the pelvic across sacral somites then migrate to caudal position
 Reach permanent position at lumbar region at 8th week
 Developed from two sources:
o Metanephric mesoderm: forms the excretory system composed of nephrons, PCT, DCT, loop of Henle
o Ureteric Bud/Metanephric diverticulum: forms the collecting system composed of collecting tubules, major and minor calyces, renal pelvis, and ureter

Front 42

urinary bladder embyro

Back 42

Usually part of the genital system
 Becomes continuous with the urogenital sinus, where the urorectal sinus will be divided into urogenital sinus (anteriorly) and anurectal canal (posteriorly)
 Upper part of the urogenital sinus forms the bladder, lower part forms the urethra
 At birth, usually in abdominal region becoming pelvic organ

Front 43

nephrons embryo

Back 43

Formed until birth, at birth kidneys are usually lobulated
 During infancy, there is the disappearance of lobulations due to increase in growth of nephrons but not in number
 Glomerular capillaries start to form by the 10th week

Front 44

urine formation embryo

Back 44

 At 10th week of fetal life
 Urine excreted will go to the amniotic cavity and be mixed with the amniotic fluid
 A mature fetus swallows several hundred liters of amniotic fluid which contain fetal urine

Front 45

kidneys embryo

Back 45

Pelvic organ becoming abdominal
 Position: developing kidneys usually in the pelvis then, it will ascend in the abdominal region (at posterior abdominal wall)
 As kidneys ascend, ureters will extend
 As development continues, the kidneys ascend and the urinary bladder descends

Front 46

bilateral renal agenesis

Back 46

No kidneys intrauterine due to absence of renal parenchyma
- Decrease in the amount of amniotic fluid thus, there will be no lung development intrauterine
- Will lead to Compression Syndrome or Potter’s Syndrome (flattened nose)

Front 47

polycystic kidney

Back 47

Failure of the union between convoluted tubules and collecting tubules causing accumulation of urine in the tubules and the ducts forming cysts
- Autosomal recessive: progressive disorder, formed in the collecting ducts; renal failure early during the first year of life or childhood
- Autosomal dominant: disease in all segments of the nephron, kidney failure until adulthood

Front 48

multicystic dysplastic kidney

Back 48

Renal parenchyma not functioning
- Will cause hypertension, renal failure
- There is the absence in the formation of ureter

Front 49

ectopic kidney

Back 49

Not located in proper position
- For instance, in pelvic kidney: during their ascent from pelvis to posterior abdominal wall, kidneys will usually pass through the arterial fork formed by the umbilical artery; however, kidneys may actually become trapped, so that it remains in the pelvis

Front 50

horsehoe kidney

Back 50

During the ascent, kidneys are trapped by the inferior mesenteric artery usually in the lumbar region
- Produced by displaced ureteric buds with fusion of their associated blastemas
- There is the fusion of inferior poles together

Front 51

double collecting system

Back 51

Two ureters (complete or partial duplication – duplication or splitting of ureteric bulb)
- Vestigial kidneys on the other ureter
- Sometimes, empty to the vaginal canal forming fistulas (prone to UTIs)

Front 52

bladder extropy

Back 52

- Very rare
- Defect in the ventral body wall caused by lack of mesodermal migration between umbilicus and genital tubercle followed by rupture of thin layer of ectoderm
- Bladder is exposed as well in the mucosa, sometimes with the bowel
- The pubic rami are separated instead of fused
- The rectus muscle is exposed and separated
 Epispadias (in males): external urethral meatus is in the ventral part of penis with concomitant undescendent testis; prone to vesticular cancer
 Hypospadias: external urethral meatus found on the inferior aspect of the penis usually near the glands; incomplete fusion of urethral folds

Front 53

hydronephros

Back 53

dilatation of renal pelvis

Front 54

vesico-urethra reflux

Back 54

Ureters are not obliquely placed causing vesicouretero reflux
 Will cause UTI, repeated infection, scarring of kidneys and renal failure