1. Renal Physiology

2. Introduction
A. The urinary system consists of two kidneys that filter the blood, two ureters, a urinary bladder, and a urethra to convey waste substances to the outside.
Kidney
Inferior vena cava
Abdominal aorta
Hilum
Renal vein
Ureters
-smooth muscle
Urinary bladder
Urethra
Renal artery
Adrenal gland
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3. Kidneys
A. The kidney is a reddish brown, bean-shaped organ 12 centimeters long; it is enclosed in a tough, fibrous capsule.
Renal pelvis
Minor calyx
Major calyx
Renal papilla
Renal pyramid
Collecting
duct
Nephrons
Renal sinus
Renal medulla
Renal capsule
Renal cortex
Ureter
Renal corpuscle
Renal tubule
Papilla
Fat
in renal sinus
Renal column

4. B. Location of the Kidneys
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B. Location of the Kidneys
1. The kidneys are positioned retroperitoneally on either side of the vertebral column between the twelfth thoracic and third lumbar vertebrae, with the left kidney slightly higher than the right.

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C. Kidney Structure
1. A medial depression in the kidney leads to a hollow renal sinus into which blood vessels, nerves, lymphatic vessels, and the ureter enter.
2. Inside the renal sinus lies a renal pelvis that is subdivided into major and minor calyces; small renal papillae project into each minor calyx.

6. a. The renal medulla houses tubes leading to the papillae.
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3. Two distinct regions are found within the kidney: a renal medulla and a renal cortex.
a. The renal medulla houses tubes leading to the papillae.
b. The renal cortex contains the nephrons, the functional units of the kidney. The site of glomerular filtration

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D. Kidney Functions
1. The kidneys function to regulate the volume, composition, and pH of body fluids and remove metabolic wastes from the blood in the process.
2. The kidneys also help control the rate of red blood cell formation by secreting erythropoietin, and regulate blood pressure by secreting renin.

9. E. Renal Blood Vessels
1. The abdominal aorta gives rise to renal arteries leading to the kidneys.
2. As renal arteries pass into the kidneys, they branch into successively smaller arteries: interlobar arteries, arcuate arteries, interlobular arteries, and afferent arterioles leading to the nephrons.
3. Venous blood is returned through a series of vessels that generally correspond to the arterial pathways. The renal vein then joins the inferior vena cava as it courses through the abdominal cavity.

10. Cortical radiate artery and vein Cortex
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Cortical radiate
artery and vein
Proximal
convoluted
tubule
Cortical radiate artery and vein
Cortex
Afferent arteriole
Arcuate vein and artery
Medulla
Efferent
arteriole
Distal convoluted
tubule
Interlobar
vein and artery
Peritubular
capillary
Renal artery
Renal vein
Renal pelvis
Ureter

11. F. Nephrons 1. Nephron Structure
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F. Nephrons
1. Nephron Structure
a. A kidney contains one million nephrons, each of which consists of a renal corpuscle and a renal tubule.
b. The renal corpuscle is the filtering portion of the nephron; it is made up of a ball of capillaries called the glomerulus and a glomerular capsule that receives the filtrate.

12. d. Several distal convoluted tubules join to become a collecting duct.
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c. The renal tubule leads away from the glomerular capsule and first becomes a highly coiled proximal convoluted tubule, then leads to the nephron loop, and finally to the distal convoluted tubule.
d. Several distal convoluted tubules join to become a collecting duct.

13. Glomerular capsule Cortical radiate artery Proximal convoluted tubule
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Glomerular
capsule
Cortical radiate
artery
Proximal
convoluted
tubule
Cortical radiate
vein
Glomerulus
Afferent
arteriole
Efferent
arteriole
Renal
cortex
Distal
convoluted
tubule
From renal
artery
Peritubular
capillary
To renal
vein
Renal
medulla
Descending
limb
Nephron
loop
Ascending
limb
Collecting duct

15. 2. Blood Supply of a Nephron
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2. Blood Supply of a Nephron
a. The glomerulus receives blood from a fairly large afferent arteriole and passes it to a smaller efferent arteriole.
b. The efferent arteriole gives rise to the peritubular capillary system, which surrounds the renal tubule.

16. 3. Juxtaglomerular Apparatus
a. At the point of contact between the afferent and efferent arterioles and the distal convoluted tubule, the epithelial cells of the distal tubule form the macula densa.
b. Near the macula densa on the afferent arteriole are smooth muscle cells called juxtaglomerular cells.
c. The macula densa together with the juxtaglomerular cells make up the juxtaglomerular apparatus, which secretes the endocrine signal, renin, into blood in the afferent arteriole

17. 물의 조절을 주로 하는 것. 이런 것을 조절하는 효소들은 j 셀에서 만들어져. Gfr은 그래서 심장의 펌핑이 중요해.
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Glomerular
capsule
Glomerulus
Afferent
arteriole
Efferent
Juxtaglomerular
apparatus
Distal
convoluted
tubule
Proximal
Nephron loop
Afferent arteriole
Glomerular capsule
Efferent arteriole
Ascending limb
of nephron loop
cells
Podocyte
Macula densa
Glomerulus는 아트리올의 변형된 형태. 들어오는 곳에 파이버가 있어서 수축이 일어남. 그러면 필터레이션에 영향을 미침. 필트레이션레이트. (GFR)
물의 조절을 주로 하는 것. 이런 것을 조절하는 효소들은 j 셀에서 만들어져.
Gfr은 그래서 심장의 펌핑이 중요해.
Glomerulus에서 밖으로 나가려는 것과 glomerular capsule 내에서 글로머룰러스로 들어가려는 삼투압의 차 net filtration pressure
심장의 펌핑에서 생기는 hydrostatic pressure는 안으로 보만주머니/glomerular capsule로 들어가려하고, osmotic, hydrostatic pressures는 반대로 나가려고 함. 이 차가 총 filtration pressure

18. Hydrostatic pressure of the cardiac pump
아트리올에 구명이 있음.

19. Urine Formation
A. Urine formation involves glomerular filtration, tubular reabsorption, and tubular secretion.

20. Substance X is filtered and secreted but not reabsorbed.
Substance Y is filtered and some of it is reabsorbed.
Substance Z is filtered and completely reabsorbed.

21. B. Glomerular Filtration
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B. Glomerular Filtration
1. Urine formation begins when the fluid portion of the blood is filtered by the glomerulus and enters the glomerular capsule as glomerular filtrate.

22. C. (Glomerular) Filtration Pressure
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C. (Glomerular) Filtration Pressure
1. The main force responsible for moving substances by filtration through the glomerular capillary wall is the hydrostatic pressure of the blood inside. The net pressure forcing substances out of the glomerulus is the net filtration pressure.
2. Due to plasma proteins, osmotic pressure of the blood resists filtration, as does hydrostatic pressure inside the glomerular capsule.

23. Hydrostatic pressure from the heart favors filtration, osmotic and hydrostatic pressures of the filtrate oppose it.

24. Outward force, glomerular hydrostatic pressure = +60 mm
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Blood
flow
Blood
flow
Plasma colloid
osmotic pressure
Glomerular
hydrostatic
pressure
Net filtration
pressure
Capsular
hydrostatic pressure
Net Outward Pressure
Outward force, glomerular hydrostatic pressure = +60 mm
Inward force of plasma colloid osmotic pressure = –32 mm
Inward force of capsular hydrostatic pressure = –18 mm
Net filtration pressure = +10 mm

25. D. (Glomerular) Filtration Rate
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D. (Glomerular) Filtration Rate
1. The factors that affect the filtration rate are filtration pressure, glomerular plasma osmotic pressure, and hydrostatic pressure in the glomerular capsule.

26. 2. When the afferent arteriole constricts in response to sympathetic stimulation, filtration rate is declined; When the efferent arteriole constricts, filtration pressure increases, increasing the rate of filtration.
F = d P/R R = 8Lvis/pr4

27. Inulin, a biologically inert polysaccharide, can be used
to estimate the GFR since it is filtered, but not reabsorbed or secreted.

28. 5. On the average, filtration rate is
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3. When osmotic pressure of the glomerular plasma is high, filtration rate decreases.
4. When hydrostatic pressure inside the glomerular capsule is high, filtration rate declines.
5. On the average, filtration rate is
125 milliliters per minute or 180 liters in 24 hours, most of which is reabsorbed further down the nephron.

29. E. Regulation of Filtration Rate
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E. Regulation of Filtration Rate
1. Glomerular filtration rate is relatively constant, although sympathetic impulses may decrease the rate of filtration.
2. Another control over filtration rate is the renin-angiotensin system, which regulates sodium excretion.
a. When the sodium chloride concentration in the tubular fluid decreases, the macula densa senses these changes and causes the juxtaglomerular cells to secrete renin.

30. d. The heart can also increase filtration rate when blood volume
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b. Secretion of renin triggers a series of reactions leading to the production of angiotensin II, which acts as a vasoconstrictor; this may, in turn, affect filtration rate.
c. Presence of angiotensin II also increases the secretion of aldosterone, which stimulates reabsorption of sodium.
d. The heart can also increase filtration rate when blood volume
is high.

31. • Vasoconstriction: affect filtration rate • Increased aldosterone
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Lung capillaries
Kidney
Liver
Renin
Angiotensin-
converting
enzyme
Angiotensinogen
Angiotensin I
Angiotensin II
Bloodstream
• Vasoconstriction: affect filtration rate
• Increased
aldosterone
secretion
ADH secretion
• Increased thirst
Release into
bloodstream
Stimulation

32. In case of 설사
- Renal sympathetic nerves는 afferent 한 것과 연관이 있어. 이 신경전달신호가 증가하면 Gfr을 줄어듬.

34. Natriuresis: increased levels of Na+ in urine
atrial natriuretic peptide
물을 많이 먹은 경우
Natriuresis: increased levels of Na+ in urine

36. Diuresis: increase in the volume of excreted urine

38. The diversity and redundancy of signals that alter water appetite, also known as “thirst,” demonstrate the importance and adaptive value of the homeostatic maintenance of blood volume and pressure.

42. In a person suffering acidosis, buffering can be gained with “new” bicarbonate ions synthesized in the tubule cells and a “sink” for H+ ions as HPO42- in the tubule.
Peritubular capillary
HCO3 – moved to capillary is synthesized to
H2CO3- under high conc of H+ in response to acidosis

43. In a person suffering acidosis, additional “new” bicarbonate ions are synthesized from catalysis of glutamine.
Peritubular capillary

45. In a kidney-failure patient undergoing dialysis, the blood is briefly removed from the body to be circulated through a dialyzer, where dialysis fluid and blood move in counter-current directions to remove nitrogenous and other wastes and adjust osmolarity before the blood is returned to the body.

46. F. Tubular Reabsorption
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F. Tubular Reabsorption
1. Changes in the fluid composition from the time glomerular filtrate is formed when urine arrives at the collecting duct are largely the result of tubular reabsorption of selected substances.
2. Most of the reabsorption occurs in the proximal convoluted tubule, where cells possess microvilli with carrier proteins.

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3. Carrier proteins have a limited transport capacity, so excessive amounts of a substance will be excreted into the urine.
4. Glucose and amino acids are reabsorbed by active transport, water by osmosis, and proteins by pinocytosis.

48. G. Sodium and Water Reabsorption
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G. Sodium and Water Reabsorption
1. Sodium ions are reabsorbed by active transport, and negatively charged ions follow passively (passive transport).
2. As sodium is reabsorbed, water follows by osmosis.

49. Na+ reabsorption from the collecting duct cells
Peritubular capillary
to bladder

50. Na+ pumping accomplishes H2O reabsorption since osmosis drives H2O to follow the movement of Na+ ions pumped across membranes.

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H. Tubular Secretion
1. Tubular secretion transports certain substances from the plasma into the renal tubule.
2. Active transport mechanisms move excess hydrogen ions into the renal tubule along with various organic compounds.

52. I. Regulation of Urine Concentration and Volume
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I. Regulation of Urine Concentration and Volume
1. Most of the sodium ions are reabsorbed before the urine is excreted, and sodium is concentrated in the renal medulla by the countercurrent mechanism.
2. Normally the distal convoluted tubule and collecting duct are impermeable to water unless the hormone ADH is present.

53. J. Urea and Uric Acid Excretion
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J. Urea and Uric Acid Excretion
1. Urea is a by-product of amino acid metabolism; uric acid is a by-product of nucleic acid metabolism.
2. Urea is passively reabsorbed by diffusion but about 50% of urea is excreted in the urine.
3. Most uric acid is reabsorbed by active transport and a small amount is secreted into the renal tubule.

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3. Potassium ions are secreted both actively and passively into the distal convoluted tubule and the collecting duct.

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K. Urine Composition
1. Urine composition varies from time to time and reflects the amounts of water and solutes that the kidneys eliminate to maintain homeostasis.
2. Urine is 95% water, and also contains urea, uric acid, a trace of amino acids, and electrolytes.

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Urine Elimination
A. After forming in the nephrons, urine passes from the collecting ducts to the renal papillae, then to the minor and major calyces, and out the renal pelvis to the ureters, urinary bladder, and finally to the urethra, which conveys urine to the outside.

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B. Ureters
1. The ureters are muscular tubes extending from the kidneys to the base of the urinary bladder.
2. The wall of the ureter is composed of three layers: mucous coat, muscular coat, and outer fibrous coat.
3. Muscular peristaltic waves convey urine to the urinary bladder where it passes through a flaplike valve in the mucous membrane of the urinary bladder.

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C. Urinary Bladder
1. The urinary bladder is a hollow, distensible, muscular organ lying in the pelvic cavity.
2. The internal floor of the bladder includes the trigone, which is composed of the openings of the two ureters and the urethra.

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3. The wall of the urinary bladder is made up of four coats: inner mucous coat, submucous coat, muscular coat made up of detrusor muscle, and outer serous coat.
a. The portion of the detrusor muscle that surrounds the neck of the bladder forms an internal sphincter muscle.

60. Openings of the ureters
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Serous coat
Ureter
Urinary bladder
Ureter
Detrusor muscle
Submucous coat
Ductus (vas)
deferens
Mucous coat
Openings of the ureters
Seminal
vesicle
Trigone
Neck
Prostate gland
Internal urethral sphincter
Prostate gland
Urethra
Region of external
urethral sphincter-composed of skeletal muscle which is under conscious control
Urethra
(a)- 오줌이 나가는 앞 뒤에 괄약근이 있.
(b)

61. 1. Urine leaves the bladder by the micturation reflex.
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D. Micturition
1. Urine leaves the bladder by the micturation reflex.
2. The detrusor muscle contracts and the external urethral sphincter (in the urogenital diaphragm) must also relax.
3. Stretching of the urinary bladder triggers the micturation reflex center located in the sacral portion of the spinal cord.
4. Return parasympathetic impulses cause the detrusor muscle to contract in waves, and an urge to urinate is sensed.

62. 5. When these contractions become strong
5. When these contractions become strong enough, the internal urethral sphincter is forced open.
6. The external urethral sphincter is composed of skeletal muscle and is under conscious control.
relaxation

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E. Urethra
1. The urethra is a tube that conveys urine from the urinary bladder to the outside via the external urethral orifice.
2. It is a muscular tube with urethral glands that secrete mucus into the urethral canal.