Renal System Flashcards
Functions of the kidney and urinary tract?
- Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
- Excrete toxic metabolic waste products
These are both achieved via the production, storage and voiding of urine - Act as an endocrine gland, producing renin and erythropoietin
Shape of the kidney?
Bean-shaped organ in the upper retroperitoneal area
Progressive structures from the kidney to the ureter?
- Minor calyces
- Major calyces
- Renal pelvis
Arrangement of the kidneys?
Cortex - extends between the medullary pyramids, forming renal columns
Medulla - divided into medullary pyramids (10-18 per kidney); the apices point towards the hilum ending on the minor calcyes (known as the papillae, form which urine drips into the renal pelvis)
Arteries within the kidney?
Interlobular arteries pass within the renal columns
Arcuate arteries arc over the renal pyramids
Components of the nephron?
Renal corpuscle
Renal tubules
What is the nephron?
Functional unit of the kidneys
Structure of the renal corpuscle?
- Glomerulus (tuft of capillaries)
- Bowman’s capsule (cup of simple squamous epithelium at the blind end of the nephron; capillaries invaginate into this)
Glomerulus is supplied by an afferent arteriole and drained by an efferent arteriole
Layers separating the blood from the glomerular filtrate?
- Capillary endothelium
- Specialised epithelium (lies on top of the glomerular capillaries) with epithelial cells called PODOCYTES
Between these 2 layers is a thicker than usual basal lamine, made up of GAGs
Arrangement of the podocytes?
Endothelium is fenestrated with pores and the podocytes have inter-digitating cell processes, which form filtration slits
Connective tissue core of the renal corpuscle?
Consists of scattered mesangial cells, which have several functions (support and removal of debris)
Structure of a proximal convoluted tubule (PCT) cell?
Have a brush border
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Histological cross-section of the PCT?
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Differences in the limbs of the loop of Henle?
Thin limb - thin, simple, squamous lining in which the nuclei typically protrude into the lumen
Transition to the thick limb
Thick limb - simple, cuboidal epithelial cells with abundant mitochondria
What is the vasa recta?
Thin-walled blood vessels that dip down into the medulla from above and then climb back up to the cortex
These loops are collectively termed the vasa recta
Differences between the DCT and PCT?
Found in the cortex and are lined by simple cuboidal epithelium
Unlike the PCT, the cells of the DCT lack a brush border of extensive microvilli
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Arrangement of the collecting ducts in the cortex?
Collecting ducts, along with the straight segments of the PCT and DCT are gather together in parallel bundles
These run perpendicular to the surface of the kidney and are called medullary rays
Arrangement of the collecting ducts in the medulla?
Appear alongside the loops of Henle and vasa recta
As they converge onto the opening at the renal papilla, they are referred to as the Ducts of Bellini
Lining of the collecting ducts?
Simple columnar epithelium
What is the juxtaglomerular apparatus?
Specialised region formed at the site where the DCT passes adjacent to the vascular pole of the SAME renal corpuscle, that forms part of its very own nephron
3 components of the juxtaglomerular apparatus?
- Macula densa
- Juxtaglomerular cells (AKA granular cells)
- Extraglomerular mesangial cells (or lacis cells)
Location and structure of the macula densa?
On the side of the DCT nearest the afferent arteriole
Cells are taller, crowded together and nuclei and intensely stained
Function of the macule densa?
Sensing NaCl in the tubular fluid at the DCT
Location and function of the juxtaglomerular cells?
AKA granular cells
Modified smooth muscle cells in the wall of the afferent arteriole
Contain/secrete renin
Location and function of the extraglomerular mesangial cells (lacis cells)?
Modified mesangial cells extending outside of the renal corpuscle
Exact function is unknown
Structure of the conducting parts of the urinary systems (urine conducting elements)?
Urine produced at the renal papilla (where the collecting duct drains into the minor calyx) is collected into and then flows via: • Minor calyx • Major calyx • Renal pelvis • Ureter • Bladder
During voiding, it flows into the urethra and exits the body
Lining of the urine conducting elements?
Almost all are lined by transition epithelium (AKA urothelium)
Below this, there is a lamine propria and 2-3 layers of smooth muscle
Cells at the luminal surface are called umbrella cells, as they are domed (AKA surface cells)
Why does the epithelium of the urinary tract have a special structure?
- Variability in thickness of cells represents different states of distension
- Apical surface of the cells at the surface have a thickened membrane to provide a highly impermeable barrier
Lining of the ureter?
- Transitional epithelium
- Lamina propria (fibroelastic connective tissue)
- Muscularis externa (smooth muscle)
Lining of the urinary bladder?
- Urothelium
- Lamina propria
- Smooth muscle layers
Structure of the urethra in females?
3-5cm in length
Initially lined by transitional epithelium, which transitions to stratified squamous (near its transition)
Structure of the urethra in males?
20cm in length:
• Prostatic urethra - extends from bladder through the prostate gland; lined by transitional epithelium
• Membranous urethra - extends from prostate to the bulb of the penis; transitional epithelium changes to stratified columnar
• Penile urethra - lined by stratified columnar epithelium which, near the tip of the penis, becomes stratified squamous
Lining of the prostate gland?
Tubulo-alveolar glands lined typically by simple columnar secretory epithelium and with a fibromuscular stroma
Its secretions make up about 1/2 the seminal fluid volume
