Summary FLG221 Renal physiology

FLG 221: Renal Physiology
Renal physiology I: Urinary functions Functional anatomy
Urinary functions
AIM: Homeostasis in body fluid – maintain body fluids at constant levels
- regulation of ECF (extra cellular fluid) volume, osmolarity (ions) & electrolyte balance by handling
water and electrolytes
- regulation of acid-base balance by controlling H+ and HCO3 – levels
- excretion of metabolic end-products and foreign substances like urea (metabolic end product of
amino acids), uric acid (metabolic end product of nucleic acids) and creatinine (metabolic end product
of creatine phosphate in muscle cells)
- retaining of adequate amounts of essential substances

Multiple Functions of the Kidneys
1. rid the body of waste materials
2. control the volume and electrolyte composition of the body fluids - maintains the stable internal
environment.
Kidneys serve many important homeostatic functions, including the following:

- Excretion of metabolic waste products and foreign chemicals
- Regulation of water and electrolyte balances
- Regulation of body fluid osmolality and electrolyte concentrations
- Regulation of arterial pressure
- Regulation of acid-base balance
- Regulation of erythrocyte production
- Secretion, metabolism, and excretion of hormones
- Gluconeogenesis

Regulation of Water and Electrolyte Balances
- For maintenance of homeostasis, excretion of water and electrolytes must match intake precisely.
- Intake of water and many electrolytes is usually governed by a person’s eating and drinking habits, requiring the kidneys to
adjust their excretion rates to match the intakes of various substances.

Regulation of Arterial Pressure
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Regulation of Erythrocyte Production
- The kidneys secrete erythropoietin, which stimulates production of red blood cells by hematopoietic
stem cells in the bone marrow.
- One important stimulus for erythropoietin secretion by the kidneys is hypoxia.
- The kidneys normally account for almost all the erythropoietin secreted into the circulation.

,Regulation of 1,25-Dihydroxyvitamin D 3 Production
- The kidneys produce 1,25-dihydroxyvitamin D 3 (calcitriol), the active form of vitamin
D, which is essential for normal calcium deposition in bone and calcium reabsorption
by the gastrointestinal tract.

Glucose Synthesis
- The kidneys synthesize glucose from amino acids and other precursors during prolonged fasting, a
process referred to as gluconeogenesis.

Physiologic Anatomy of the Kidneys
General Organization of the Kidneys and Urinary Tract
- The two kidneys lie on the posterior wall of the abdomen, outside the peritoneal cavity
- Is about the size of a clenched fist.
- The medial side of each kidney contains an indented region called the hilum through which pass
the renal artery and vein, lymphatics, nerve supply, and ureter, which carries the final urine from
the kidney to the bladder, where it is stored until the bladder is emptied.
- The kidney is surrounded by a tough fibrous capsule that protects its delicate inner structures.
- Two major regions that can be visualized are the outer cortex and the inner medulla regions.
- The medulla is divided into 8 to 10 cone-shaped masses of tissue called renal pyramids.
- The base of each pyramid originates at the border between the cortex and medulla and
terminates in the papilla, which projects into the space of the renal pelvis, a funnel-shaped
continuation of the upper end of the ureter.
- The outer border of the pelvis is divided into open-ended pouches called major calyces that extend
downward and divide into minor calyces, which collect urine from the tubules of each papilla.
- The walls of the calyces, pelvis, and ureter contain contractile elements that propel the urine
toward the bladder, where urine is stored until it is emptied by micturition

The kidneys

, Functional anatomy of the kidney




Nephron