-Zoo 251: Chapter 23- excretion & gross anatomy

excretion: process of separating wastes from the body fluids and eliminating them from the body
carried out by 4 organ systems:
- respiratory- carbon dioxide, small amounts of other gases & water
- integumentary system- water, inorganic salts, lactate, and urea in sweat
- digestive- not only eliminates food residue (which is not a process of excretion) but also actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, and other metabolic wastes
- urinary- a broad variety of metabolic wastes, toxins, drugs, hormones, salts, hydrogen ions, and water
POSITION AND ASSOCIATED STRUCTURES:
kidneys lie against posterior abdominal wall at the level of vertebrae T12 to L3
right kidney slightly lower than left
- bc of the space occupied by the large right lobe of the liver above it
rib 12 crosses approx. middle of left kidney
kidneys are retroperitoneal, along with uterus, urinary bladder, renal artery and vein, and the adrenal glands
GROSS ANATOMY:
weighs 150g, 11cm long, 6 cm wide, and 3 cm thick
lateral surface convex
medial surface concave & has a slit-hilum- that admits the renal nerves, blood vessels, lymphatics, and ureter
connected by 3 layers of connective tissue
- fibrous renal fascia
  - binds kidney and associated organs to the abdominal wall
- perirenal fat capsule
  - cushions kidney and holds it in place
- fibrous capsule
  - protects it from trauma and infection
suspended by collagen fibers that extend from the fibrous capsule, through the fat, to the renal fascia
renal fascia fused with peritoneum anteriorly & w the fascia of the lumbar muscles posteriorly
kidneys drop about 3 cm when one goes from lying down to standing- getting out of bed
renal parenchyma- glandular tissue that forms the urine- appears C-shaped in frontal section
- encircles the medial cavity, the renal sinus, occupied by blood and lymphatic vessels, nerves, and urine-collecting structures
- adipose tissue fills the remaining space in the sinus and holds these structures in place
- divided into 2 zones- outer renal cortex & inner renal medulla
- the boundary between the cortex and medulla is called the corticomedullary junction
- extensions of the cortex called renal columns project toward the sinus and divide the medulla into 6 to 10 renal pyramids
  - each pyramid is conical, with a broad base facing the cortex & a blunt point called the renal papilla facing the sinus
  - one pyramid and the overlying cortex constitute one lobe of the kidney
- the papilla of each renal pyramid is nestled in a cup called a minor calyx,
  - collects its urine
- 2 or 3 minor calyces converge to form a major calyx
- 2 or 3 major calyces converge in the sinus to form the funnel-like renal pelvis
- the ureter is a tubular continuation of the renal pelvis that drains the urine down to the urinary bladder