Kidney Flashcards
Explain the anatomy of the urinary system?
Located in the abdominal and pelvic cavity
Anatomically linked with the reproductive system (urogenital system)
Pair of kidneys
Pair of ureters Bladder Urethra
What is the function of the urinary system?
- The most important function of the urinary system - to maintain homeostasis
• Osmoregulation
• Ionic regulation (sodium, chloride, potassium, chloride etc.)
• Regulation of Blood Pressure
• Regulation of blood pH
• Hormone production - Erythropoietin
• Activation of Vitamin D - Nitrogenous excretion – to remove nitrogenous waste products (urea, uric acid, creatinine) and excess water from the body
What are the kidneys?
Paired
Bean shaped, heart shaped, lobulated Colour = Deep reddish-brown
Dorsal part of the abdominal cavity
Ventral to the first lumbar vertebrae Retroperitoneal
No mesenteric attachment (tunica adventitia)
Right kidney lies slightly cranial to the left
What is the kidney made up of?
Capsule
– protective layer of fibrous tissue
Hilus
– point at which blood vessels, nerves and the ureters
Lobes (up to 18)
Cortex- dark red outermost layer (or shell) Includes renal corpuscles
Medulla- slightly paler
Medullary pyramids collecting ducts, loops of Henle
Renal sinus
Renal Pelvis – connective fibrous tissue
Calyces
Renal papilla➔minor c➔major c ➔renal pelvis➔Ureter
What is the nephron?
functional unit of the kidney
What are the parts of the nephron?
- Renal corpuscle
- Bowman’s capsule (visceral and parietal layer) - Glomerulus - Tubes
- Proximal convoluted tubule (PCT) -Loop of Henle
- Distal convoluted tubule (DCT) -Tubules join to form collecting ducts
What is the renal blood supply (Arterial)?
Arterial blood flow
- Renal artery
- Segmental artery
- Interlobar artery
- Arcuate artery
- Interlobular artery (again)
- Afferent arterioles
- Glomerulus
- Efferent arterioles
What is the renal blood supply (Venous)?
Venous blood flow
- Peritubular capillaries
- Vasa recta renis
- Interlobular vein
- Arcuate vein
- Interlobar vein (again)
- Renal vein
- Caudal vena cava
What are the functions of the nephrons?
– 1. Regulate blood volume and conc. – 2. Control blood pH.
– 3. Filter out toxins.
What are the three stages of filtration?
- Glomerular filtration
Small molecules and ions move from glomerulus (capillaries ) into the Bowman’s capsule due to hydrostatic pressure or pressure gradient. - Selective tubular reabsorption
From the proximal convoluted tubule to the capillary plexus via diffusion, facilitate diffusion, osmosis and active transport. - Selective tubular secretion
Substances are removed from the blood to the tubule via active transport.
What is glomerular filtration (ultrafiltration)? And what is it achieved by?
Plasma in the glomerulus is filtered into urinary space of Bowman’s capsule
Substances separated by molecule size:
ions (Na, K, Ca, PO4), glucose, amino acids, urea, creatinine, vitamins & small plasma proteins
Most plasma proteins and erythrocytes retained
➔Glomerular filtrate (useful & harmful subs.)
Achieved by: Adequate BP Selectively permeable pores in: - capillary endothelium - basement membrane on which capillaries lie - inner layer of Bowman’s capsule Extensive filter area
What is selective tubular reabsorption?
Most filtrate materials are reabsorbed. Mainly by active transport.
Cells of the proximal convoluted tubule (PCT) have:
walls with numerous microvilli - abundant mitochondria
Glucose
normally all is reabsorbed
mechanism is linked to sodium reabsorption
Amino acids
- also reabsorbed by active transport - also linked to sodium uptake
Sodium & chloride
- removal of sodium leads to chloride ions following passively
Protein - recovered by pinocytosis at microvilli bases
Water
- moves by osmosis
- PCT walls are highly permeable
Urea - some diffuses back into the blood
Proximal Convoluted Tubule (PCT): –Creatinine and Histodine secreted
Distal Convoluted Tubule (DCT): –Potassium (K) into the filtrate
Both PCT and DCT secrete H ions to regulate pH of body fluids
What is osmoregulation?
Urine dilution
-more salt is reabsorbed in the DCT
- DCT is almost impermeable to water
Urine concentration
- depends on the loop of Henle (birds & mammals) which generates a gradient of salt conc.
[counter current multiplier arrangement] –high salt conc. in the peritubular fluid &
raised permeability of the collecting ducts
= water passes by osmosis into the peritubular fluid
= urine concentration raised
What is the counter current multiplier?
Loop of Henle works as a Counter Current Multiplier.
What is ADH and what is its function?
ADH (vasopressin) = hormone synthesised in hypothalamus, released from posterior pituitary, promotes water retention and vasoconstriction
Important in water balance and in long term maintenance of blood pressure
Rapid response using negative feedback
