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External Kidney Anatomy
- Renal hilus: medial surface, leads into renal sinus
- 3 layers of supportive tissue:
- a. Renal Capsule
- b. Adipose capsule
- c. Renal Fascia
Three internal layers
- Pelvis (lateral to hilus)
Renal (medullary) pyramids
Contain mostly collecting ducts; area of medulla between two renal columns
Renal Columns (cortical tissue)
Pyramid and its adjacent cap of cortical tissue
branching extensions of pelvis forming cup-shaped areas enclosing papillae of pyramids.
carries blood to glomerulus.
carries blood away from glomerulus
wrapped around proximal and distal convoluted tubules.
wrapped around loop on Henle
Functional unit of Kidney
- Nephron: two types
- a. Cortical (85%) and juxtamedullary
- b. juxtamedullary- long into medulla; ability to increase concentration
Nephron = renal tubule + ?
Renal corpuscle = glomerulus + ?
- 1. Glomerulus
- 2. Bowman's capsule
Loop of Henle
- Descending and ascending limbs
- Thin and thick segments
Beginning of DCT lies against afferent and efferent arterioles. Juxtaglomerular cells secrete renin- adjusts blood pressure through vasoconstriction.
3 functions of kidney
- 1. Filtration
- 2. Absorption
- 3. Secretion
- Passive process
- Net filtration pressure- glomerular blood pressure is opposed by colloid osmotic pressure and capsular hydrostatic pressure
glomerular filtration rate
GFR is directly proportional to blood pressure. High blood pressure= more filtrate
Intrinsic control of Glomerular filtration
- renal autoregulation
- Myogenic mechanisms: when arterioles are stretched, the constrict
- Tubuloglomerular feedback mechanisms: senses change in osmolarity or pressure and vasocontricts to slow rate of filtration.
What triggers renin release?
- reduced stretch of JG cells (ie decreased blood pressure)
- When macula densa cells sense how low NaCl they stimulate renin release.
- tubule cells have tight junctions
- Virtually all organic material reabsorbed
- movement active or passive
- Actively reabsorbed
- enters luminal side of the cell passively; exits basolateral membrane actively ; enters peritubular capillaries passively
Electrical Gradient: movement of Na causes gradient to move Cl- which creates an osmotic gradient so that water follows sodium
What compounds are linked to Na transport
glucose, animo acids, lactate, vitamins and most cations
Which part of the different tubules is most absorbent
- Proximal convoluted tubule.
- All glucose, lactate, aa is absorbed here (coupled with Na)
Where is uric acid absorbed?
Proximal convoluted tubule
Loop of Henle (absorption and secretion methods)
- Water can leave the descending limb, but not ascending limb
- Na, water, Urea, Cl- reabsorbed in the thin segement of loop
- Thick segment actively absorbs K, Cl- and Na+
- therefor, lumenal contents become more dilute in ascending loop.
What controls the absorption of Na+ ?
- Decreased BP, plasma Na+ or increased K+
- Increases Na+ absorption from DCT
Distal Convoluted Tubule (absorption and secretion)
- absorbs Na+, Cl -, H2O and secretes K+ and H+
- Absorption of water is controlled by ADH acting at the collection ducts
- Atrial Natriuretic peptide- increased BP causes release; decreases Na+ absorption
What controls the absorption of Ca++ ?
- permeable to water, not salt
- at the bottom of duct, in inner medulla, permeable to urea
Osmotic concentration ______ from cortex to medulla (inc or dec)
Loop of Henle and vasa recta are _________ systems
Volume of plasma from which a particular substance completely cleared by kidneys in a given time.
Inulin (NOT insulin)
- neither secreted or reabsorbed; acts as a marker.
- Renal clearance rate of insulin equals GFR