A&P Urinary system

urinary system functions

• filtration

• excretion

• homeostasis

filtration

removal of metabolic waste products from the blood

excretion

release of waste products via urine

• creatine (produced muscle contractions)

• urea (produced during the break down of proteins)

homeostasis

maintain electrolyte balance, pH, blood pressure, and RBC count

how is blood volume and pressure regulated?

by adjusting the water content of urine and producing the erythropoietin hormone

erythropoietin

stimulates RBC production

how are blood electrolytes regulated?

through the absorption or elimination of K+, Na+, and Cl-

how is blood pH maintained?

by excreting bicarbonate ions and uric acid

kidney location

against the deep muscles of the back and the floating ribs

• high in abdominal cavity

• against the dorsal body wall

• one on each side of the spine

• retroperitoneal

• left kidney→ extends from T12 to L3

• right kidney → under liver, slightly lower

size of kidney

fist

external anatomy of kidney

• convex laterally (a)

• medial indentation is the renal hilus (b)

• enclosed by fibrous renal capsule

• adrenal gland sits on superior surface (c)

Where does unfiltered blood enter through?

renal artery

where does filtered blood leave through?

renal vein

what is the kidney protected by?

renal capsule

Renal capsule

made of dense connective tissue

• protects/surrounds the kidney

renal medulla

inner portion of the kidney, made of cone-shaped renal pyramids

• deep to the cortex, darker in color

• contains 6-18 renal pyramids

renal pyramid

• have a stripped appearance due to bundles of urine-collecting tubes

renal cortex

the outermost tissue, with columns that dip between the pyramids

• most superficial region

renal pelvis

funnel-shaped sac that collects secreted urine

• leads to the ureter

renal calyxes

branches of the renal pelvis

• cup shaped area that collects urine from the base of the pyramids

• several calyces drain into the renal pelvis

renal hilum is also called

medial indentation

ureter

tubes of smooth muscle that propel/drains urine from the kidneys to the urinary bladder

• extend from the renal pelvis → posterior bladder

• ~ 25 - 30 cm long & 3-4 mm in diameter

each ureter empties into the bladder at an opening called the ureteral orifice

nephrons

the functional unit of the kidney

Where does filtration take place? which two structures?

• glomerulus

• glomerular capsule

filtration

• pushes fluids and solutes smaller than proteins out of blood and into the glomerular capsule

• no-selective, passive process

what are the two main structures of a nephron?

• glomerulus

• renal tubule

glomerulus

cluster of capillaries that receives pressurized blood

glomerular capsule

a cup-like sac which receives filtrate from glomerulus

renal tubule

cup-shaped capsule that surrounds the glomerulus on one end, then twists and coils for about 3 cm before leading to a collecting duct

what is the capsule surrounding the glomerulus also called?

bowman’s capsule

urine production (2)

• filtration

• reabsorption

• secretion

reabsorption

mostly in the proximal tubule, but also along the length of the renal tubule and collecting duct

• water, glucose, amino acids, and needed ions from filtrate to re-enter capillary blood

  • diffusion and active transport

secretions

• peritubular capillaries into the renal tubule → urine

• urea, creatine, drugs, and certain ions are secreted

what are the capillaries and glomerular capsule are lined with?

simple squamous epithelium that is selectively permeable

what does filtrate contain?

• water

• urea

• creatine

• ammonia

• electrolytes

tubular reabsorption

prevents the release of too much water or electrolytes

active transport

pulls salts out of the nephron into the renal medulla, creating a hypertonic environment

osmosis

moves water into the hypertonic medulla

peristalsis

smooth muscle contractions

where is urine stored?

urinary bladder

urethra

thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis

• internal urethral sphincter

hypothalamus

detects low blood pressure and low blood volume stimulates the posterior pituitary to release ADH

Antidiuretic hormone (ADH)

causes the kidneys to conserve more water and produce more concentrated urine

released in response to high solute concentration in the blood plasma

• inhibited by alcohol

• produced by the hypothalamus → posterior pituitary

what is urine color an indication of?

hydration status

pH of urine

slightly acidic, pH around 6

turbidity of urine

should be clear or transparent

specific gravity of urine

slightly higher than pure water; indicates concentration

urinalysis

often preformed with test strips which can detect the presence of drugs, proteins, glucose, blood cells, and other substances

what does dark urine suggest?

dehydration and/or elevated ADH levels

kidney stones

form when solutes in urine forms large, solid crystals that get stuck in a calyx, ureter, or urethra

• hard mineral/salt deposits that form in the kidneys

• lithotripsy

calcium stones

forms due to dehydration

uric acid stones

form due to excessive animal protein intake

urinary tract infections (UTI)

caused by bacteria growing in the urinary tract

• more common in women due to a wider, shorter urethra

• treated with antibiotics

kidney failure

occurs when the kidneys are no longer able to filter wastes from blood normally

• causes: high bp and diabetes

dialysis

uses a machine to remove wastes/filters from blood in place of the kidneys

• typically takes 3-5 hours, 3 days a week

• average life expectancy is 5-10 years

kidney transplants

surgically insert a donor kidney into the lower abdomen at the iliac artery and vein

Final composition of urine

• 0,2% creatine, ammonia, uric acid

• 2.8% electrolytes

• 2.0% urea

• 95% water

Are leukocytes normally in urine?

no

What does the presence of leukocytes indicate?

indicates urinary tract infection

what do the presence of erythrocytes indicate?

can enter urine if the ureters, bladder, or kidneys are damaged

bilirubin

made from the breakdown of hemoglobin and is what makes urine yellow

What do high levels of bilirubin indicate?

sign of liver disease

what do the presence of proteins indicate?

excessive exercise

What foods lower pH of urine?

fish, meat, cheese

what foods raise pH of urine?

fruits and veggies

what does the presence of glucose indicate?

may be diabetic

ketones

byproducts of lipid metabolism

what can elevated levels of ketones mean?

lipid metabolism is happening very quickly

• keto diets cause this

• can lower blood pH

specific gravity

measures the salinity/electrolyte level of pH

what do elevated levels of specific gravity suggest?

severe dehydration

urea

• a component of urine

• waste product produced by the breakdown pf proteins in food

How much percent of total blood volume passes through the kidneys each minute?

20-25&

how many liters of urine do the kidneys produce each day?

1-2 L

urinary bladder

hollow muscular sac that stores urine before it’s eliminated

• size & shape varies depending on the amount of urine it’s holding

• located posterior to the pubic symphysis

internal urethral sphincter

INVOLUNTARY muscle that keeps urethra closed most of the time

• smooth muscle

female urethra

3-4 cm long

• external opening lies anterior to the vagina

male urethra

~ 20 cm long

• passes through the penis

micturition (voiding/urination)

flow of urine is controlled by two sphincters

urine is forced past the internal sphincter

what triggers bladder contractions?

stretch receptors in the bladder wall

external sphincter

VOLUNTARY skeletal muscle

what type of waste do the kidneys excrete?

nitrogenous waste

where is majority of the water in the body found?

• intracellular fluid (in cell)

• extracellular fluid (outside cell)

  • interstitial fluid

  • blood plasma

water output

• urine

• sweat

• lungs & skin

• feces

water intake

ingestion of food and beverages

• metabolism

osmolarity

water concentration in blood plasma

how do the kidneys control osmolarity

by controlling how much water is reabsorbed in the nephron/ released from the body in urine

electrolytes

substances that form ions in solution

• kidneys control the excretion of several ions

• important to proper body functions

  • water balance

  • nerve signals

  • muscle contractions

normal blood pH

7.35-7.45

how do the kidneys change blood pH?

by excreting H+ ions/conserving HCO3- ions to regulate acid-base balance

renin

triggers a series of reactions that constrict blood vessels and raise blood pressure

• produced by kidney

aldosterone

steroid hormone produced by the adrenal cortex

function: regulate salt & water balance

• presence of aldosterone increases the reabsorption of sodium which increases blood volume, and blood pressure

polycystic kidneys

inherited congenital defect in which the kidneys develop clusters of cysts

• kidneys lose function over-time and kidney failure may result

lithotripsy

a procedure using sound waves to break up kidney stones

incontinence

inability to hold urine in the bladder

common causes: pressure on bladder from coughing, laughing, or lifting something heavy, urge incontinence

urge incontinence

sudden intense urge to urinate followed by an involuntary loss of urine

urinary retention

inability to completly empty the bladder

• can be acute/chronic

• most common cause in men: enlarged prostate gland

embryonic development

fetal kidneys begin excreting urine by the 10th week of pregnancy

the urine is released into the amniotic fluid

infants

filtration rate increases quickly during the first two weeks of life

• newborn babies have limited ability remove excess sodium and to concentrate & dilute urine

toddlers

toddlers are eventually able to control the voluntary urethral sphincter and are ready for toilet training

• the kidneys are fully mature and functioning by age 2

elderly

kidney mass and function begins to decline with age

• urinary tract infections and other diseases that affect the kidneys are more common in people over 60