Urinary System Human Body Systems

glomerulus

a capillary bed where blood filtration takes place. it is in the nephron of a kidney.

afferent arterioles

a group of blood vessels that provide the nephrons and in turn kidneys with blood. It enters Bowman's Capsule first before the other one.

kidney

a pair of bean shaped organs found along the posterior wall of the abdominal cavity. the left kidney is located slightly higher than the right kidney because the right side of the liver is much larger than the left side. the kidneys, unlike the other organs of the abdominal cavity, are located posterior to the peritoneum and touch the muscles of the back. the kidneys are surrounded by a layer of adipose tissue that holds them in place and protects them from physical damage. the kidneys filter metabolic wastes, excess ions, and chemicals from the blood to form urine.

ureter

a pair of tubes that carry urine from the kidneys to the urinary bladder. the ureters are about 10 to 12 inches long and run on the left and right sides of the body parallel to the vertebral column. gravity and peristalsis of smooth muscle tissue in the walls of the ureters move urine toward the urinary bladder. the ends of the ureters extend slightly into the urinary bladder and are sealed at the point of entry to the bladder by the ureterovesical valves. these valves prevent urine from flowing back towards the kidneys.

proximal convoluted tube

PCT. the first section of a nephron before the loop of henle. it regulates the PH of the filtrate. Does not have blood anywhere in it. 65% of all absorption occurs here. all glucose back to blood. some water back in blood.

reabsorption

things that are let out of the blood into the nephron are taken back up into the blood.

distal convoluted tube

this is the section of a nephron directly after the loop of henle and directly before the collecting duct. hormonally controlled.

filtration

this occurs in the glomerulus. it cleans the blood and takes some stuff out of it.

peritubular capillaries

where secretion takes place in a nephron. Also where absorption occurs as well as the exchange of gases. It regulates water and electrolyte balance.

renal cortex

where several of the distal convoluted tubules merge and form a collecting duct, which in turn passes into the renal medulla, becoming larger and larger as it joins other collecting ducts. It is the part of the kidney where ultrafiltration occurs.

medullary pyramid

each kidney has between 7-15 of these. they consist of tubes through with the urine produced in the outer portion of the kidney travels. the end of it extends into the cup-shaped calyx where the urine collects, then is passed to the bladder.

efferent arterioles

form a convergence of the capillaries of the glomerulus. They exit the glomerulus right after it ends.

loop of henle

forms a long loop in the medulla of the kidney, from which water and salts are reabsorbed back into the blood.

secretion

from the blood to the nephron. occurs in the peritubular capillaries.

major calyx

2 or 3 of minor calyces converge to form this, through which urine passes before continuing through the renal pelvis into the ureter. It propels urine through the pelvis and ureters to the bladder.

bladder

a sac-like hollow organ used for the storage of urine. it is located along the body's midline at the inferior end of the pelvis. urine entering the urinary bladder from the ureters slowly fills the hollow space of the bladder and stretches its elastic walls. the walls of the bladder allow it to stretch to hold anywhere from 600 to 800 milliliters of urine.

bowman's capsule

a structure surrounding the glomerulus of each nephron in the kidneys that extracts wastes, excess salts, and water from the blood.

urinalysis

a test that determines the content of the urine. its contents can provide vital health information.

glomerular filtration rate

a test to check how well the kidneys are working. it regulates how much blood passes through the glomeruli each minute.

urine

also called filtrate. It is one of the body's main ways of eliminating excess water and salt from the body.

minor calyx

chambers of the kidney through which urine passes. They surround the apex of the renal pyramids. Utine formed in the kidney passes through a renal papilla at the apex into here. 2 or 3 converge to form a major calyx.

collecting duct

connects the nephrons to the ureter. It connects all the nephrons.

renal pelvis

the area at the center of the kidney. urine collects in here and is funneled into the ureter. it acts as a filter for urine before it passes out of the kidney and into the bladder. it is a cup shaped open cavity. It expands or retracts in response to the volume of urine.

nephron

the functional unit of the kidney. there are 1 million per kidney. they filter the blood and regulate the body's water and electrolyte balance.

urethra

the tube through which urine passes from the bladder to the exterior of the body. It is also an organ of the male reproductive system as it carries sperm out of the body through the penis. the flow of urine through the urethra is controlled by the internal and external urethral sphinctor muscles. the internal sphinctor is made of smooth muscle and opens involuntarily when the bladder reaches a certain set level of distention. the opening of the internal sphinctor results in the sensation of needing to urinate. the external urethral sphinctor is made of skeletal muscle and may be opened to allow urine to pass through the urethra or may be held close to delay urination.