Excretory System grade 12

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Renal Vein

in urinary system, takes filtered blood from kidney —> heart

Renal Artery

in urinary system, takes unfiltered blood from heart —> kidney

Urethra

in urinary system, discharges urine out controlled by sphincters

Ureter

in urinary system, carries urine from kidney —> bladder by peristalsis

Kidney

in urinary system, filtered blood and makes urine

Nephrons

in kidney that spans from the renal cortex —> renal medulla

• main parts, filter, tubule, collecting duct

• filters blood and produces urine

Glomerulus

part of nephron, network of capillaries from renal artery bring blood into nephron.

• impermeable to large ions

• permeable to small ions

Bowmans Capsule

part of nephron, receives filtrate from glomerulus

Tubule

in nephron, reabsorption of useful substances from filtrate

1. Proximal Convoluted tubule

2. loop of henle

3. distal convoluted tubule

Collecting duct

• Gets filtrate from distal collecting duct

• Final site for water reabsorption and urine concentration

• Regulated by ADH (antidiuretic hormone)

• water is passively reabsorbed by osmosis causes [] of solute to become 4x as concentrated making it urine

Afferent Arteriole

part of blood network in nephrons, brings unfiltered blood into glomerulus for filtration

Efferent Arteriole

Part of blood network in nephron, takes away blood that has been filtered to body

Peritubular Capillaries & Vasa recta

reabsorption of materials in bloodstream, secretion of metabolic waste and medication

• reabsorb water, ions, glucose, and amino acids

• Secrete waste products into the tubule

Venules and Renal Vein

collects (venule) then returns (vein) filtered blood from kidneys —> heart

Glomerular Filtration

• H2O and small solutes from blood go into bowman’s capsule by moving down [] gradient

• large solutes stay in blood

Tubular Secretion

filtrate is reabsorbed, majority of reabsorption is at PCT

• reabsorbed water via osmosis

• uses active transport for Na+

• electrical attraction for negatively charged ions (Cl-)

• secretes H+ to maintain blood pH

Descending limb of loop of Henle

• permeable to H2O, impermeable to solutes

• H2O will diffuse out of filtrate via osmosis into medulla

• inner medulla is saltier allowing H2O to continue diffusing as it moves down medulla

• by the bend in the loop the filtrate is extremely concentrated because of the loss of H2O

Thin portion of Ascending loop of Henle

• impermeable to H2O, slightly permeable to solutes

• Na+ passively diffuses from high [] to low [] from filtrate —> renal medulla

Thick portion of ascending loop of Henle

• actively transports Na+ from filtrate —> renal medulla

• K & Cl- passively diffuse out

Reabsorption from DCT —> blood

Active Na+ reabsorption depends on body

passive reabsorption, negatively charged ions because of electrical attraction

Secretion from blood —> distal tubule

• active secretion of H+, urea, NH3

• passive secretion of K+ if there is excess

• passive transport of meds, toxins

Renin - Angiotensin Aldosterone System

Maintains blood pressure, fluid balance, and electrolyte levels.

Juxtaglomerular cells

from kidneys, release renin which is an enzyme that catalyzes angiotensinogen

angiotensinogen

helping regulate blood pressure and fluid balance after activation by renin.

Aldosterone

• Increases sodium (Na⁺) reabsorption in the distal tubules and collecting ducts of the kidney.

• Promotes water retention (follows Na⁺).

• Increases potassium (K⁺) excretion.

• produced by the adrenal cortex

Acid Base Buffer System

• CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

Kidney acid-base buffer system

maintain acid-base balance by reabsorbing bicarbonate, secreting hydrogen ions, and producing new buffers