Urinary System - Part 1

Renin

Hormone secreted by the kidney that raises blood pressure

Erythropoietin

A hormone produced and released by the kidney that stimulates the production of red blood cells by the bone marrow.

Nitrogenous waste
Toxins
Drugs excess ions

Waste products that kidneys dispose in urine

Kidneys
Ureters
Urinary bladder
Urethra

Organs of the urinary system

T12 to L3

Location of kidneys in the level of vertebrae

Right kidney

Which kidney is lower due to the position of the liver

Dorsal body in a retroperitoneal position

Location of the kidneys

12 cm (5 inches) long, 6 cm (2.5 inches) wide

Structure of the kidney in an adult

Renal hilum

A medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves)

Adrenal glands

A pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress.

Fibrous capsule

A transparent capsule that prevents infections in surrounding regions from spreading to the kidney

Perirenal fat capsule

a fatty mass that surrounds the kidney and cushions it against blows

Renal fascia

Protective outer covering of the kidney made of dense fibrous connective tissue

Hydronephrosis

Abnormal condition of water in the kidney

Renal cortex

Outer region of the kidney

Renal medulla

Inner region of the kidney

Renal pyramids or medullary pyramids

Triangular regions with a striped appearance present in the medulla

Renal columns

Extensions of the cortex that project inward toward sinus and separates the pyramids

Renal pelvis

Medial region flat, funnel-shaped reservoir that collects the urine and passes it to the ureter

Calyces (calyx)

The cuplike structures which drain urine from the collecting ducts, inside the pyramids and into the renal pelvis.

one-quarter

___ of the total blood supply of the body passes through the kidneys each minute

Renal artery

Bblood vessel that carries blood to the kidney

segmental arteries

renal artery approaches the hilum, it divides into

interlobar arteries

segmental arteries further divide into these arteries which supply blood to the arcuate arteries

arcuate arteries

small vessels found at the base of the renal pyramids; appear as echogenic structures

cortical radiate arteries

branch off the arcuate arteries and ascend into the cortex

Nephrons

Functional units of the kidneys

renal corpuscle and renal tubule

two parts of the nephron

glomerulus

a knot of capillaries inside the glomerular capsule where pores produce a blood filtrate and is made up of podocytes

podocytes

make up inner wall of Bowman's capsule and filters filtrate through slits

Glomerular capsule (Bowman's capsule)

Cup-shaped, hollow structure surrounding glomerulus

foot processes

cling to the glomerulus

filtration slits

create a porous membrane-ideal for filtration

renal tubule

microscopic tubes in the kidney where urine is formed after filtration; extends from glomerular capsule and ends when it
empties into the collecting duct

1. Proximal convoluted tubule (PCT)
2. Nephron loop (loop of Henle)
3. Distal convoluted tubule (DCT)

From the glomerular (Bowman’s) capsule, the subdivisions of the renal tubule are:

cortical nephrons

Most nephrons are called __ because they are located almost entirely within the cortex

Juxtamedullary nephrons

Found at the cortex-medulla junction; nephron loop dips deep into the medulla

collecting ducts

collect urine from both types of nephrons, through the renal pyramids, to the calyces, and then to the renal pelvis

1. Glomerulus
2. Peritubular capillary bed

Two capillary beds associated with each nephron

Glomerulus

Fed and drained by arterioles; specialized for filtration; high pressure forces fluid and solutes out of blood and into the glomerular capsule

Afferent arteriole

arises from a cortical radiate artery and feeds the glomerulus

Efferent arteriole

receives blood that has passed through the glomerulus

Peritubular capillary beds

Arise from the efferent arteriole of the glomerulus; low-pressure, porous capillaries; adapted for absorption instead of filtration; cling close to the renal tubule to receive solutes an water from tubule cells; drain into the interlobar veins

1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

Urine formation is the result of three processes

Glomerular filtration

nonselective, passive process in which glomerulus is a filter

glomerular capillary walls
proteins and blood cells

Water and solutes smaller than proteins are forced through __; these are normally too large to pass through the filtration membrane

filtrate

Once in the capsule, fluid is called

renal tubule

Filtrate leaves via the

normal

Filtrate will be formed as long as systemic blood pressure is

too low

If arterial blood pressure is too low, filtrate formation stops because glomerular pressure will be __ to form filtrate

oliguria

abnormally low urinary output; between 100 and 400 ml/ day

anuria

abnormally low urinary output; less than 100 ml/day

- Water
- Glucose
- Amino acids
- Ions

The peritubular capillaries reabsorb useful substances
from the renal tubule cells, such as:

Proximal Convoluted Tubule

Most reabsorption occurs in the

Tubular secretion

In this process, reabsorption in reverse

- Hydrogen and potassium ions
- Creatinine

Some materials move from the blood of the peritubular
capillaries into the renal tubules to be eliminated in filtrate

drugs and excess ions

Secretion is important for getting rid of substances not already in the filtrate such as

blood

Tubular secretion is also important for maintaining acid-base balance of

ureter

Materials left in the renal tubule move toward the

Nitrogenous wastes

waste products that are poorly reabsorbed, if at all; tend to remain in the filtrate and are excreted from the body in the urine

Urea

Nitrogenous waste that are end product of protein breakdown

Uric acid

Nitrogenous waste that are released when nucleic acids are metabolized

Creatinine

Nitrogenous waste that are associated with creatine metabolism in muscle tissue