Histology Flashcards
How does the kidney act as an endocrine gland?
Produces:
- Renin - Erythropoietin
What is the kidney covered by?
Thin, strong, collagen capsule
What is the medulla divided into and what direction do they point in?
Pyramids:
- Apices point to hilum (papillae)
What is each nephron composed of?
Renal corpuscle
Renal tubules
What is the approximate length of each nephron?
45-65mm
What is the renal corpuscle formed from?
Glomerulus
Bowman’s capsule
What epithelium makes up the Bowman’s capsule?
Simple squamous
How many cell layers separate the blood and glomerular filtrate? What are these layers?
Two:
- Capillary endothelium - Specialised epithelium on top of capillaries: - Podocytes
What do the podocytes form?
Filtration slits (~25nm wide)
What lies between the cell layers separating the blood and glomerular filtrate?
Thicker basal lamina (0.3μm instead of 0.05μm):
- Made of Glycosaminoglycan (GAGs)
What forms the mesangium and what does it do?
Mesangial cells
Functions as connective tissue core:
- Support
- Removes debris
Where does the Loop of Henle lie?
In the renal medulla
What is the structure of the cells lining the thin descending limb of the Loop of Henle?
Simple squamous
Nuclei protrude into lumen
What is the structure of the cells lining the thick ascending limb of the Loop of Henle?
Simple cuboidal
Abundant mitochondria
Where is the distal convoluted tubule found?
Cortex
What lines the distal convoluted tubule?
Simple cuboidal epithelium
What does the DCT lack that the PCT has?
A brush border
Where do the collecting ducts run alongside?
Straight segments of PCT and DCT in cortex
Coupled with the structures collecting ducts run alongside, what is the name for these bundles?
Medullary rays:
- Parallel bundles
What direction do the medullary rays run?
Perpendicular to kidney surface
In the medulla, what do the collecting ducts run alongside?
Loops of Henle
What epithelium lines the collecting ducts?
Simple columnar
Where do the juxtaglomerula apparatuses form?
At site where DCT passes:
- Adjacent to vascular pole of same renal corpuscle
What are the three components of the juxtaglomerular apparatus?
Macula densa
Juxtaglomerular cells
Extraglomerular mesangial cells/Lacis cells
Where does the macula densa lie?
On side of DCT closest to afferent arteriole
What are the features of the DCT cells?
Taller
Crowded
Intensely stained nuclei
What do macula densa do?
Sense DCT ion composition
What are the juxtaglomerular cells and what do they do?
Modified smooth muscle in afferent arteriole wall
Contain and secrete renin
What are the extraglomerular mesangial cells?
Modified mesangial cells that extend out of the corpuscle
What type of the epithelium is the urothelium?
Transitional stratified epithelium (3-6 cells)
What are the cells at the luminal surface of the urothelium?
Umbrella cells (domed): - Special thickened and inflexible membrane
Why does the urothelium have a special structure?
Variable thickness:
- Different states of distension
Apical surface of cells have a thickened membrane:
- Impermeable
What lies below the urothelium and what is it?
Lamina propria:
- 2-3 layers of smooth muscle
How long is the urethra in women?
3-5cm
What epithelium is the female urethra?
Transitional and then stratified squamous
How long is the urethra in men?
~20cm
How long is the prostatic urethra and what lines it?
3-4cm
Transitional epithelium
How long is the membranous urethra, where does it like and what lines it?
~1cm:
- From prostate to bulb of penis
Transitional -> Stratified columnar epithelium
How long is the penile urethra and what lines it?
~15cm Stratified columnar (stratified squamous at tip of penis)
What glands form the prostate gland?
Tubulo-alveolar
What type of epithelium are the tubules in the prostate gland lined with?
Simple columnar secretory epithelium with fibromuscular stroma
What fraction of seminal fluid volume is made up of prostate gland secretions?
~1/2