Removal of Urine

Urine is drained from the renal pelvis and carried by the ureter to the urinary bladder (Fig. 13-4). Urine is stored in the bladder until fullness stimulates a reflex contraction of the bladder muscle and expulsion of urine through the urethra. The female urethra is short (4 cm; 1.5 in) and carries only urine. The male urethra is longer (20 cm; 8 in) and carries both urine and semen.

The voiding (release) of urine, technically called micturition or urination, is regulated by two sphincters (circular muscles) that surround the urethra. The upper sphincter, just below the bladder, functions involuntarily; the lower sphincter is under conscious control.

Interior The Urinary Bladder

FIGURE 13-4. Interior of the urinary bladder, shown in a male subject. The trigone is a triangle in the floor of the bladder marked by the openings of the ureters and the urethra. (Reprinted with permission from Cohen BJ, Wood DL. Memmler's The Human Body in Health and Disease. 9th Ed. Philadelphia: Lippincott Williams & Wilkins, 2000.)

Y hern i

NORMAL STRUCTURE AND FUNCTION

Antidiuretic A hormone released from the pituitary gland that causes reab-

hormone (ADH) sorption of water in the kidneys, thus concentrating the urine an-ti-di -u-RET-ik

angiotensin

A substance that increases blood pressure; activated in the blood

an-je-o-TEN-sin

by renin, an enzyme produced by the kidneys

calyx

A cuplike cavity in the pelvis of the kidney; also calix (plural,

KA-liks

calyces) (root cali, calic)

erythropoietin (EPO)

A hormone produced by the kidneys that stimulates red blood

e-rith-ro-POY-e-tin

cell production in the bone marrow

glomerular capsule

The cup-shaped structure at the beginning of the nephron that

glo-MER-u-lar KAP-sul

surrounds the glomerulus and receives material filtered out of

the blood

glomerular filtrate

The fluid and dissolved materials that filter out of the blood and

glo-MER-u-lar FIL-trat

enter the nephron at the Bowman capsule

gloomeruluos

The cluster of capillaries within the glomerular capsule (plural,

glo-MER-u-lus

glomeruli) (root glomerul/o)

kidney

An organ of excretion (root ren/o, nephr/o); the two kidneys filter

KID-no

the blood and form urine, which contains the waste products of

metabolism and other substances as needed to regulate the water

and electrolyte balance and the pH of body fluids

mictuorition

The voiding of urine; urination

mik-tu-RISH-un

nephron

A microscopic functional unit of the kidney; working with blood

NEF-ron

vessels, the nephron filters the blood and balances the composi-

tion of urine

reonal cortex

The outer portion of the kidney

RE-nal KOR-tex

renal medulla

The inner portion of the kidney; contains portions of the

me-DUL-la

nephrons and tubules that transport urine toward the renal

pelvis

renal pelvis

The expanded upper end of the ureter that receives urine from

PEL-vis

the kidney (root pyel/o, from the Greek word for pelvis, mean

ing "basin")

renal pyramid

A triangular structure in the medulla of the kidney composed of

PIR-a-mid

the loops and collecting tubules of the nephrons

reonin

An enzyme produced by the kidneys that activates angiotensin in

RE-nin

the blood

Normal Structure and Function, continued

tubular reabsorption

The return of substances from the glomerular filtrate to the blood

TUB-u-lar re-ab-SORP-shun

through the peritubular capillaries

urea

The main nitrogenous (nitrogen-containing) waste product in the

u-RE-a

urine

ureter

The tube that carries urine from the kidney to the bladder (root

U-re-ter

ureter/o)

urethra

The tube that carries urine from the bladder to the outside of the

u-RE-thra

body (root urethr/o)

urinary bladder

The organ that stores and eliminates urine excreted by the

U-ri-nar-e: BLAD-der

kidneys (root cyst/o, vesic/o)

ulrinatilon

The voiding of urine; micturition

u-ri-NA-shun

ulrine

The fluid excreted by the kidneys. It consists of water, elec-

U-rin

trolytes, urea, other metabolic wastes, and pigment. A variety

of other substances may appear in urine in cases of disease

(root ur/o).

Box 13-1 Words That Serve Double Duty

Some words appear in more than one body system to represent different structures. The medulla of the kidney is the inner portion of the organ. Other organs, such as the adrenal gland, ovary, and lymph nodes, may also be divided into a central medulla and outer cortex. But medulla means "marrow," and this term is also applied to the bone marrow, to the spinal cord, and to the part of the brain that connects with the spinal cord, the medulla oblongata.

A ventricle is a chamber. There are ventricles in the brain and in the heart. The word fundus means the back part or base of an organ. The uterus has a fundus, the upper rounded portion farthest from the cervix, and so does the stomach. The fundus of the eye, examined for signs of diabetes and glaucoma, is the innermost layer where the retina is located. A macula is a spot. There is a macula in the eye, which is the point of sharpest vision. There is also a macula in the ear, which contains receptors for equilibrium.

In interpreting medical terminology, it is often important to know the context in which a word is used.

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Responses

  • sabrina
    What is the function of the urethra?
    7 years ago
  • wesley
    What is the two structures that surround the urinary bladder?
    6 years ago
  • neftalem
    What is the base of the bladder?
    2 years ago
  • landolfo
    What is the medical term for the ‘inner portion of the kidney’?
    1 year ago

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