Urinary System Functions and Organs

Functions of the Urinary System

• The urinary system filters and eliminates waste products from blood
• It helps maintain electrolyte balance and regulate fluid levels in the body
• It contributes to blood pressure regulation
• It produces hormones involved in red blood cell production and calcium metabolism

Urinary System Organs

• Kidneys (two) produce urine
• Urinary tract consists of:
  • Ureters that transport urine towards the urinary bladder
  • Urinary bladder that temporarily stores urine prior to urination
  • Urethra

Homeostatic Function of the Urinary System

• Regulates blood volume and blood pressure by adjusting the volume of water lost in urine
• Regulates plasma ion concentrations by controlling the quantity of sodium, potassium, chloride, and other ions lost in urine
• Calcium level is controlled through the synthesis of calcitriol
• Helps control blood pH by controlling the loss of hydrogen and bicarbonate ions in urine
• Conserves valuable nutrients by preventing their loss while removing metabolic wastes (e.g., urea and uric acids)
• Assists the liver in detoxification of poisons and deamination of amino acids during starvation

Kidney Structure

• Located on either side of the vertebral column, with the left kidney slightly superior to the right kidney
• The superior surface of the kidney is capped by the adrenal gland
• The kidney is positioned overlying the peritoneum, in the back of the abdominal cavity, and supported by connective tissue
• Attached to the aorta and inferior vena cava
• Blood enters the kidney through the renal artery and leaves through the renal vein
• Each kidney is enclosed in a renal capsule surrounded by adipose tissue

Internal Kidney Structures

• Renal cortex
• Renal medulla
• Renal pyramids
• Renal columns
• Minor and major calyces
• Renal pelvis

Protective Layers of the Kidney

• Fibrous capsule (layer of collagen fibers covering the outer surface of the entire organ)
• Perinephric fat (thick layer of adipose tissue surrounding the fibrous capsule)
• Renal fascia (dense fibrous outer layer anchoring the kidney to the surrounding tissue)

Kidney Functions

• Filters blood
• Produces urine

Adult Kidney Characteristics

• 10 cm long and weighing 150 grams

Hilum

• Prominent medial indentation
• Point of entry for the renal artery and renal nerves
• Point of exit for the renal vein and ureter

Renal Cortex

• Superficial region of the kidney in contact with the fibrous capsule
• Reddish-brown and granular

Renal Pyramid

• 6-8 triangular structures in the renal medulla
• Base of each pyramid abuts the renal cortex
• Tips (renal papilla) project into the renal sinus

Kidney Lobes

• Consist of renal pyramid, renal cortex, and renal columns

Ducts within the Renal Papilla

• Discharge urine into a minor calyx, a cup-shaped drain

Minor and Major Calyces

• Major calyces are formed by 4-5 minor calyces
• Minor calyces receive urine from the papilla of one renal pyramid
• Once the filtrate enters the calyces, it becomes urine because no further reabsorption can occur

Renal Pelvis

• Large funnel-shaped chamber
• Formed by 2/3 major calyces
• Connected to the ureter, which drains the kidney

Blood Supply to the Kidney

• Kidney receives 20-25% of total cardiac output
• About 1200 ml of blood enters each minute
• Receives blood from the artery

Nephron

• The microscopic functioning unit of the kidney, with each kidney having millions
• Consists of renal corpuscle (filtering blood plasma) and renal tubule (filtered fluid passes through)
• Renal tubule empties into a collecting system

Parts of the Nephron

• Renal corpuscle (spherical structure)
  • Glomerular (Bowman's) capsule (outer wall of the renal corpuscle, encapsulating glomerular capillaries and continuous with the initial segment of the tubule)
  • Glomerulus (capillary network)

Understand the functions and organs involved in the Urinary System, including filtering waste, maintaining electrolyte balance, and regulating fluid levels.