Urinary System

Where is the thirst center located?

Hypothalamus - activated by dec. blood psi/vol. or inc. blood osmolarity or dry mouth

What type of feedback is fluid regulation?

Negative feedback

3 factors of blood circulation that regulate fluid balance

Blood volume, blood pressure, blood osmolarity

Hilum

Medial indentation of each kidney - where vessels, nerves, + ureters connect

Endocrine component of kidneys

Adrenal glands - corticosteroids (cortex) + adrenaline/norepi (medula)

Renal cortex

Outer region of kidney - corpuscles + convoluted tubules

Renal medulla

Inner region of kidney - renal pyramids (loops of Henle + collecting ducts)

Renal columns

Extensions of cortical tissue that extend down between renal pyramids

Nephron

Microscopic filtration unit of the kidney - renal corpuscle + renal tubule

Renal corpuscle

Part of cortex - glomerulus + surrounding capsule (Bowman’s)

Renal tubule

Proximal convoluted tubule —> loop of Henle —> distal convoluted tubule

Is the collecting duct part of a nephron?

No

Collecting duct

Fusion of many collecting tubules from various nephrons - carries urine deeper into the kidney

Renal artery

Delivers +O2 blood to each kidney from abdominal aorta

Renal vein

How blood leaves the kidney, drains into inferior vena cava

Filtration

Movement of water + solutes out of glomerulus into bowman’s capsule

Tubular reabsorption

Substances move from tubular fluid into the blood

Tubular secretion

Substances move from the blood into tubular fluid

Main organs of the urinary system

Kidneys, ureters, bladder, urethra

Function of kidneys

Filter blood, eliminate waste via urine, regulate blood vol. + psi + pH + electrolytes, produce some hormones

Ureters

Transport urine from kidneys to bladder via peristalsis

Glomerulus

Tuft of capillaries - filter blood

Bowman’s capsule

Surrounds glomerulus - collects fluid filtered out of the blood by the glomerulus

Parts of the renal tubule

PCT, descending limb of nephron loop + ascending limb of nephron loop, DCT

Proximal convoluted tubule

Reabsorption

Descending limb of nephron loop

Where water leaves the filtrate

Ascending limb of nephron loop

Where salts are reabsorbed from the filtrate

Distal convoluted tubule

Fine-tunes the filtrate before draining it into the collecting duct

Efferent arteriole sends blood ________ the glomerulus

Away from

Afferent arteriole sends blood _______ the glomerulus

Toward

Function of the nephron loop

Concentrate urine

Edema is excess _______ fluid

Interstitial (extracellular)

Extracellular fluid

Outside of cells - 1/3 of total body fluid - interstitial fluid + blood plasma

Intracellular fluid

Inside cells - 2/3 of total body fluid

How much of skeletal muscle is water?

75%

How much of adipose tissue is water?

25%

How much of the human body is water?

45-75% - depends on age + body composition

Percentage of body water ________ with age

Decreases

Hypotonic

Diluted blood plasma - causes H2O to leave blood plasma + enter cells (cells swell)

Hypertonic

Concentrated blood plasma - causes H2O to move from the cells into blood plasma (cells shrink)

Sources of fluid intake

Drinks, food, metabolism (H2O is byproduct of aerobic cellular resp.) - xs IV fluids, fluid sequestration (edema)

Mechanisms of fluid output

Sweat, expiration (H2O vapor), feces, urination, hemorrhage, vomiting

Papillary duct

Base of renal pyramids - where urine leaves collecting ducts

Minor calyx

Collects urine from papillary ducts

Major calyx

Where several minor calyxes drain into

Renal pelvis

Receives urine from major calyxes - moves to ureter

Pathway of urine out of the kidney

Papillary ducts —> minor calyx —> major calyx —> renal pelvis —> ureter

Where does tubular fluid become urine?

Papillary duct (end of collecting duct)

Where is filtrate located?

Glomerular capsule only

Net filtration pressure (NFP)

The overall pressure in the renal corpuscle that determines if filtration occurs - blood hydrostatic + colloid osmotic + capsular hydrostatic

Glomerular filtration rate (GFR)

The rate at which filtrate is formed

A higher (pos.) NFP ______________ the GFR

Increases

Tubular secretion

Secreting more wastes from the blood into the tubular fluid - asc. limb

Tubular reabsorption

Reabsorbing substances from tubular fluid back to the blood - PCT + desc. limb

Average daily volume of urine

1-2 L