Chapter 25: The Urinary System

diuretic

diuretic

is a compound that increases urine volume.

Parathyroid hormone

(PTH) is an 84-amino acid peptide produced by the parathyroid glands in response to decreased circulating Ca++ levels.

Natriuretic hormones

are peptides that stimulate the kidneys to excrete sodium an effect opposite that of aldosterone.

Endothelins

21-amino acid peptides, are extremely powerful vasoconstrictors.

Renin

is an enzyme that is produced by the granular cells of the afferent arteriole at the JGA.

tubuloglomerular feedback

mechanism involves the JGA and a paracrine signaling mechanism utilizing ATP, adenosine, and nitric oxide (NO).

myogenic mechanism

regulating blood flow within the kidney depends upon a characteristic shared by most smooth muscle cells of the body.

Autoregulation

is a process by which an organism or system maintains its internal environment in a relatively constant state, regardless of external changes.

juxtamedullary nephrons

About 15 percent of nephrons have long loops of Henle that extend deep into the medulla and are called

systemic edema

This “plumps up” the tissues and cells, a condition termed

Sympathetic nerves

are part of the autonomic nervous system, which is responsible for the body's involuntary functions such as digestion, heart rate, and blood pressure.

glomerular filtration rate (GFR)

The volume of filtrate formed by both kidneys per minute is termed the

Angiotensin II

is a systemic vasoconstrictor that helps to regulate blood pressure by increasing it.

juxtaglomerular cell

A second cell type in this apparatus is the

macula densa

The wall of the DCT at that point forms a part of the JGA known as the

juxtaglomerular apparatus (JGA)

• Lying just outside Bowman’s capsule and the glomerulus is the

fenestrations

prevent filtration of blood cells or large proteins, but allow most other constituents through.

renal corpuscle

The glomerulus and Bowman’s capsule together form the

Nephrons

are the “functional units” of the kidney; they cleanse the blood and balance the constituents of the circulation.

renal hilum

is the entry and exit site for structures servicing the kidneys: vessels, nerves, lymphatics, and ureters.

renal columns

are connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla, the renal pyramids and renal papillae.

medulla

inner region called the

renal cortex

A frontal section through the kidney reveals an outer region called the

Micturition

is a less-often used, but proper term for urination or voiding.

detrusor muscle

The bladder is a highly distensible organ comprised of irregular crisscrossing bands of smooth muscle collectively called the

trigone

The urethra in both males and females begins inferior and central to the two ureteral openings forming the three points of a triangular-shaped area at the base of the bladder called the

urethra

transports urine from the bladder to the outside of the body for disposal.

Leukocyte esterase

is released by leukocytes; if detected in the urine, it can be taken as indirect evidence of a urinary tract infection (UTI).

polyuria

Excessive urine production is

Urinalysis

(urine analysis) often provides clues to renal disease.

urochrome

This yellow pigment is

oliguria

Output below this level may be caused by severe dehydration or renal disease and is termed

anuria

The virtual absence of urine production is termed