Anatomy and Physiology II - Chapter 18: Urinary System

This goes over the Urinary System. The specific course is Anatomy and Physiology II (BIOL-2402)

advantages of drinking water

more energy, better metabolism/critical thinking/muscles, decreased risk of constipation, decreased blood pressure, and flushing of toxins

kidney

• water, pH, ion and blood pressure regulation

• waste excretion

• erythropoietin (RBC production) and calcitriol (GI calcium absorption + kidney reabsorption)

kidney location

retroperitoneal

• behind peritoneal cavity and parietal peritoneal membrane

ureters

tubes from kidney → bladder

urinary bladder

stores urine

urethra

carries urine from bladder → outside

• males: urine + sperm

• females: only urine

nephron

functional unit of the kidney

• 1 kidney has about a million that filter out 180 L of filtrate and produce 2 L of urine a day

flow of blood in kidney

renal artery (oxygenated, high O₂) →

afferent arterioles (bigger) →

glomerular capillaries →

efferent arterioles (smaller) →

peritubular capillaries (O₂ down, CO₂ up in exchange)

→ renal vein (deoxygenated)

glomerulus

part of kidney that filters the blood

• modified capillary bed

  • fenestrated capillaries

filtration

in glomerulus

• removes: filtrate of small molecules and ions (glucose, amino acid, urea, water, Na⁺, K⁺, and Ca⁺⁺) from blood

• keeps: large molecules and cells (formed elements, plasma proteins) in blood

filtration and blood pressure

• too high → damage glomerulus

• too low → filtration doesn’t work

inner workings of afferent arterioles

afferent arteriole → macula densa cells of the distal tubule → granular juxtaglomerular cells → efferent arteriole

• when pressure drops → constricts to increase pressure

• when pressure rises → dilates to decrease pressure

glomerular filtration rate (GFR)

controlled by negative feedback mechanisms

• juxtaglomerular apparatus: detects low GFR and causes the afferent arterioles to dilate/smooth muscle to relax

  • baroreceptors

  • macula densa

  • juxtaglomerular cells

    • renin, angiotensinogen, ACE, angiotensin II

juxtaglomerular apparatus (GFR)

senses when GFR is low by using

• baroreceptors

• macula densa

makes changes using

• juxtaglomerular cells

baroreceptors (GFR)

pressure detectors, can sense when blood flow is low

• in juxtaglomerular apparatus

macula densa (GFR)

detects low Na⁺ and Cl^-

• in distal convoluted tubule of the juxtaglomerular apparatus

juxtaglomerular cells (GFR)

secretes renin

• in juxtaglomerular apparatus

renin (GFR)

liver’s angiotensinogen → angiotensin I

angiotensin converting enzyme (ACE) [GFR]

from lung, angiotensin I → angiotensin II

angiotensin II (GFR)

vasoconstrictor for efferent arteriole to raise blood pressure

reabsorption

in proximal convoluted tubule that’s lined with simple cuboidal epithelium + microvilli for absorption

if there is too much of something that is normally reabsorbed, it will be filtered out

• reabsorbs: water, glucose, amino acids, Ca⁺⁺, Na⁺, Cl^- back into blood

• doesn’t absorb: nitrogen waste (urea, uric acid, creatinine), PO₄^-3, K⁺ → tubules → urine

nitrogen waste

filtered out and not reabsorbed by the kidney

• urea, uric acid, creatinine

urea

made by the liver, goes into blood and is filtered out by the kidney

deamination of amino acids/proteins (removal of amino groups)

why is urea made?

amine group → ammonia (which is very basic →

liver turns it into urea, which is less toxic and organic

uric acid

nitrogen base (usually purine) destruction → waste product

creatinine

muscle’s creatine waste product

loop of henle

allows for more water absorption, longer in desert animals

• way to conserve water

hypothalamus thirst center

stimulated when dehydrated

anti-diuretic hormone (ADH)

released from pituitary gland whenever the hypothalamus senses hypertonic blood plasma

• increases distal convoluted tubules + collecting ducts’ water channel permeability → more water absorption

• adjusts to water consumption to change urine output (more water → less ADH, dehydrated → more ADH)

diabetes insipidus/pituitary diabetes

pituitary gland produces too little ADH → kidney produces too much urine

osmosis

diffusion of water

tries to dilute concentrate

• high water/low concentrate (hyperosmotic/hypotonic) → low water/high concentrate (hypoosmotic/hypertonic)

countercurrent exchange

• loop of henle

  • descending limb

  • ascending limb

• vasa recta

• outside medulla

descending limb of the loop of henle (countercurrent exchange)

filtrate progressively loses water and becomes more concentrated/hypoosmotic

ascending limb of the loop of henle (countercurrent exchange)

pumps out Na⁺, K⁺, and Cl^- from filtrate → filtrate becomes more concentrated/hypoosmotic

vasa recta (countercurrent exchange)

capillaries of the medulla, absorbs water from the loop of henle

outside medulla (countercurrent exchange)

very hypertonic, so it also absorbs water

secretion

in distal convoluted tubule to remove ions (K⁺, H⁺, PO₄^-3) from plasma

• regulated by hormones

  • parathyroid hormone

  • aldosterone

parathyroid hormone (secretion)

from parathyroid gland

• when Ca++ is low in the blood →

  • Ca++ reabsorption up

  • bone destruction → PO_4^-3 is secreted/removed

aldosterone (secretion)

from adrenal gland

• when Na⁺ is low/K⁺ is high in the blood →

  • Na⁺ reabsorption up

  • K⁺ is secreted/removed

albumin

liver’s plasma protein for osmotic pressure regulation in the blood plasma

• if low → blood capillaries leak water → edema, usually in ascites

  • causes:

    • liver disease (cirrhosis)

    • missing essential amino acids (kwashiorkor)

    • urinating too much albumin (kidney disease and pregnancy)

ascites

extra fluid around abdominal cavity’s organs

cystitis

bladder infection/inflammation, a UTI

• causes: e. coli (or other gut bacteria), diarrhea, wiping from back to front (anus → urethra), intercourse, thong

• prevention: water to flush out bacteria from the urethra, not holding urination, hygiene before/after intercourse

why are females more prone to cystitis/UTIs

urethra is very close to vagina and anus

so if you wipe back to front, those bacteria can enter the urethra

nephroliths

kidney stones that form in the renal pelvis → ureter → bladder → urethra

• symptoms: pain, internal bleeding, nausea, bloody urine

• causes: dehydration/low urine, dietary factors, gout, hypercalcemia (too much calcium or malfunctioning parathyroid/thyroid gland), too much oxalic acid (spinach)

• treatment: lithotripsy

lithotripsy

destruction of kidney stones through outside vibrations

not used for gallstones because they’re too sensitive