Urinary System

Anatomy and Physiology

- Major filtering system of your body

● Aids the cardiovascular system (circulatory system) by

- cleansing the blood of metabolic waste

- Flushing excess fluid from the body

- constantly works to maintain homeostasis

Functions

Performs 4 major functions:

1. Filtration - kidneys separate metabolic waste from the blood; these waste products are

formulated into urine which is stored and then expelled.

2. Waste storage and excretion - after the kidneys produce urine, it is carried to the urinary

bladder through the ureters where it is stored until it is excreted.

3. Hormone Production - kidneys produce hormones needed for essential functions

- Erythropoietin: protein that stimulates red blood cell production in bone marrow

- Calcitriol: active form of vitamin D that aids in digestion by promoting calcium

absorption in small intestine

4. Homeostasis maintenance - urinary system and the kidneys play a vital role in helping

maintain homeostasis

- Monitor blood pressure and adjust blood volume (amount of water in blood) in

response, to an increase or reduction in blood pressure

- Control pH levels (acidity or alkalinity)

- Regulate balances of fluid and electrolytes

- electrolytes - minerals that become ions (electrically charged particles) when

dissolved in water which are essential to various physiological processes to

include heart, muscle and nerve function. I.e. sodium, chloride ,potassium,

calcium, phosphate and magnesium

Organs and Structures of the Urinary System

● Kidneys - two bean-shaped organs located in the retroperitoneal cavity (part of the

abdominal cavity situated behind the peritoneum, or membrane that lines the walls of

the abdomino-pelvic cavity , protected by adipose tissue and connective tissue which

holds the kidneys in place against the muscles of the trunk; fist-sized and only weigh

4-6 oz

Filtered waste products are discharged from the body via urination (micturition;

voiding)

3 regions of the Kidney:

- Renal Cortex - outer layer of the kidney, contains more than 1 million nephrons

(basic structure of the kidney, functional unit responsible for processes of

filtration, reabsorption, secretion which create urine

● Filtration - separating waste products from the blood which reaches teh

kidney through the renal artery

● Reabsorption - blood reclaims useful substances from filtrate that flows

through renal tubules (occurs in tiny capillaries surrounding each tubule)

MOST of the water, sugar, eturn from filtrate to the bloodstream IF these substances are not already

at normal limits; if levels are below normal, the substances are

reabsorbed. What is not reabsorbed stays in the tubules until they are

secreted in urine.

● Secretion - opposite of reabsorption. Waste products like urea and

creatinine as well as some water are pushed into tubules for excretion

(urine is about 5% waste products and 95% water)

- Renal Medulla - inner region of the kidney; contains many triangle-shaped tissue

sections called medullary pyramids which each contain tubules that carry urine

from the renal cortex to the renal calyces. Renal calyces are cup-like cavities

that collect urine

- Renal Pelvis - widened upper part of the ureter (tube that urine flows from the renal calyces to the urinary bladder); lies on medial side of the kidney.

Kidneys have the ability to work harder than normal. Normal kidney functions

require only a small portion of each nephron to be used. This means if one stops

working, the other is capable of taking over functioning for both

● Ureters - two narrow tubes, 10-12 inches in length, transport urine from renal pelvises

to the urinary bladder (moves via gravity and peristalsis)

● Urinary bladder - commonly referred to as the bladder, hollow, muscular organ in the

anterior portion of the pelvic cavity; serves as reservoir, or storage, for urine until it can

be expelled. Urine gets to the bladder via the ureteral openings

● Urethra - tube that transports urine from the bladder to the outside of the body. Male is

approximately 8 inches in length and the female is approximately 1.5 inches. Female

urethra is part of the urinary system, the male’s is part of the urinary AND the

reproductive system.

Urinary tract - consists of:

- Ureters

• Urinary bladder

- Urethraminerals as well as some salt and vitamins