BSC2086: urinary system

Urinary System (components)

Two kidneys, ureters

Urinary bladder

The urethra

The Urinary System (Func.)

Filter blood and eliminate wastes/toxins

Regulate water elimination

Regulation electrolytes and acid/base balance

Secrete erythropoietin 

Synthesize calcitrol

Regulate Water Elimination (3 ways)

Blood volume

Blood Pressure

Osmolarity

Erythropoietin (func)

RBC production

Calcitroil (func)

Calcium homeostasis and bones

Kidneys (anatomy)

Pair, retroperitoneal organs

Convex laterally and concave medially

Kidney Hilum

Allows nerves, vessels, lymphatics, and ureter admission

The kidney is protected by

Rena Fascia, Perirenal Fat Capsule, Fibrous Capsule

Renal Fascia

Fiberous, deep to parietal peritoneum

Renal Fascia (func)

Binds the kidney and its organ to the abdominal wall

Perirenal Fat Capsule

Adipose tissue

Perirenal Fat Capsule (func)

Cushions the kidney and holds it in place

Fibrous Capsule

Anchored at the hilum

Fibrous Capsule (func)

Protects the kidney from trauma and infection

The Bladder

Collects urine from the uterus

Bladder (retro or intra peritoneal)

Retro

Urethra

Transports urine from bladder to outside of the body

Urethra (Proximal and Distal histology)

Lined with transitional epithelium proximally

Non - keratinized squamous epithelium distally

Internal Urinary Sphincter

Smooth Muscle, Involuntary

External Urinary Sphincter

Skeletal Muscle, Voluntary

External Urethral Orifice

Anterior to vaginal wall in female

End of penis in males

Trigone

Area at base of bladder with two ureteral opening and one urethral opening

Male Urethra (3 sections)

Prostatic, Membranous, and Spongy/Penile

Nephrons

Functional Unit of the Kidney

Nephrons (func)

Filter blood; reabsorb what is needed; secrete specific wastes; excrete what is left in the tubule as urine

Cortical Nephrons

Located just beneath the renal capsule

Juxtamedullary Nephrons

Close to the medulla and have very long nephron loops

Filtration (nephrons)

Involves mass movement of plasma contents into the renal tubule

Filtration (specific or Nonspecific)

Nonspecific

Filtration(location)

Renal corpuscle

Reabsorption (Nephrons)

Needed substances are returned to the blood (water/solutes)

Reabsorption (specific or Nonspecific)

Both

Reabsorption (location)

Renal tubule (70% in PCT)

Secretion (func)

Deliberate removal of substances from blood to table; usually toxins, drugs, and excess of substances

Secretion (specific or nonspecific)

Specific

Secretion (location)

Mainly in DCT but also PCT and collecting ducts

Excretion (func)

What does in urine and leaves the body

Excretion formula

Excretion = Filtration - Reabsorption + Secretion

Renal Corpuscle (func)

Filters blood plasma

Renal Corpuscle (parts)

Bowmans Capsule and glomerulus

Bowmans Capsule

Cup - like sac that surrounds glomerulus

Bowmans Capsule (histology/func)

Parietal layer is simple squamous
Visceral layer is podocytes that form filtration slits

Glomerulus

Tangle of fenestrated capillaries

Glomerulus (func)

Filters plasma out of the blood and into Bowmans capsule

Glomerular Filtration Rate

Volume of filtrate formed by both kidneys per unit of time

GFR (amount in L/day)

~180L/day

Under normal circumstances the hydrostatic pressure at the glomerulus is […]

higher than osmotic pressure, which allows for filtration

Renal Tubule

returns 99% of filtrate to circulation and produces urine from the remaining portion

Proximal Convoluted Tubule

Longest and most coiled segment of the tubule

PCT (Filtration and Secretion)

70% of filtration, some secretion

PCT (Histology)

walls are cubical to columnar with microvilli; lots of mitochondria

Loop of Henle (func)

uses concentration gradient and reabsorbs excess water and solute; concentrates urine

Descending limb (LoH)

highly permeable to water/low permeability to solutes and urea

Ascending Limb (LoH)

Not permeable to water/permeable to solutes via passive or active transport

Distal Convoluted Tubule

Regulates levels of solutes

Distal Convoluted Table (Secretion)

Majority of secretion from blood to filtrate

Collecting Ducts

Continuous with nephron; receive input from multiple DCTs

Collecting Ducts (func)

Use medullary concentration gradients to reabsorb water and further concentrate urine

Summary of Renal Corpuscle

Filters most of what is in the blood using a variety of methods to reabsorb needed substances. Toxins or substances present in excess are secreted into the filtrate. The filtrate then leaves the collecting duct as urine and makes its way out of the kidney for excretion from the body.

GFR determines…

solute and water concentration, and therefore osmolality and blood pressure

Sympathetic Input…

reduces GFR and redirects blood from the kidneys to other organs

Renal Autoregulation

Allows filtration to remain constant over a range of blood pressure

Myogenic Reflex

Adjusts flow from afferent arteriole

Tubuloglomerulofeedback Mechanism

Involves the signaling mechanism to adjust afferent arteriole

Juxtoglomerular Apparatus

Location of intimate contact of DCT and afferent and efferent arterioles

Macula Densa

cubical epithelial cells inside the DCT

Macula Densa (func)

Monitor fluid in the DCT; Release ATP that will be converted to adenosine

Juxtoglomerular Cells (Granular Cells)

Modified smooth muscle cells lining the afferent arteriole

Juxtoglomerular Cells (func)

Adenosine from Macula Densa cause vasoconstriction; produce renin

What signals the secretion of renin enzyme

drops in blood pressure

Where is angiotensinogen produced

The liver

Angiotensinogen is converted to

Angiotensin I

Angiotensin I is converted to Angiotensin II via

Angiotensin Converting Enzyme (ACE)

Angiotensin II (func)

Raise BP, reduce water loss, vasoconstriction, and thirst
Stimulates adrenal cortex to secrete aldosterone

Aldosterone (func)

Promotes Na and H2O reabsorption by DCT and collecting duct
Stimulates posterior pituitary to secrete ADH

ADH (antidiuretic hormone) (func)

Promotes H2O reabsorption by collecting duct and stimulates thirst

Aldosterone

Salt retaining steroid hormone secreted by the adrenal cortex

ADH

Secreted by posterior pituitary in response to decreased blood volume or increased osmolarity

Fluid Compartments

Locations that are largely separate from another compartment by some physical barrier

Intracellular Fluid (ICF)

Fluid enclosed in plasma membranes of cells

Extracellular Fluid (ECF)

Fluid that surrounds all cells in the body

ECF examples

Plasma, Interstitial fluid, CSF

Water Intake

mostly comes through the digestive tract via liquids and food, regulated by thirst

Water Output

mostly via the kidneys as urine

Water Output Sources (besides kidneys)

evaporation, sweating, and lungs

Vasopressin

Another name for ADH, controls the amount of water reabsorbed in collecting ducts

Atrial Natriuretic Peptide (ANP) Hormone (released by)

increased blood flow to heart/increased BP

ANP Hormone Effects

Vasodilation

Inhibit aldosterone release

inhibit ADH release

Six Most Important Electrolytes

Sodium, Potassium, Chloride, Bicarbonate, Calcium, Phosphate

Major Intracellular Ions

K, PO4, Proteins

K (func)

Regulates pH

Establishes RMP

Aldosterone increases tubular secretion

Major Extracellular Ions

Na, Cl, HCO3

Na (func)

Important water balance

Neuron and muscle function

HCO3 (func)

Major buffer of H+ in plasma

Kidneys are main regulators

Respiratory control of CO2 …

controls carbonic acid levels

Acid base imbalances are caused by

anything impairing respiratory function

High CO2 =

acidosis

Low CO2 =

alkalosis

when blood pH goes down

Acidosis occurs

when blood pH increases

alkalosis occurs