Urinary System Overview

Urinary System Overview

• The urinary system is composed of organs that filter blood, maintain fluid balance, and eliminate waste.
• Key organs include two kidneys, two ureters, one urinary bladder, and one urethra.

Objectives of the Lecture

• Students should be able to list the organs of the urinary system.
• Students should be able to describe the anatomy of the kidney, including relationships to surrounding structures.
• Students should be able to describe the anatomy of the ureters, including constrictions.
• Students should be able to describe the anatomy of the urinary bladder.
• Students should be able to describe the anatomy of the male urethra, including its parts.
• Students should be able to describe the anatomy of the female urethra.
• Students should know the differences between the male and female urethra.

Kidney Anatomy

• Kidneys are located on either side of the vertebral column.
• Each kidney extends from the 12th thoracic vertebra to the 3rd lumbar vertebra.
• The right kidney is slightly lower than the left.
• The kidney is approximately 12 cm long, 6 cm wide, and 3 cm thick.

Kidney Structure

• The kidney has two surfaces, two borders, and two ends.
• The lateral border is convex, the medial border is convex at the ends and concave in the middle.
• The hilum is found in the middle of the medial border and provides passage for renal vessels, nerves, and the pelvis.
• The pelvis is a dilated sac that extends outside the hilum and connects with the ureter.

Kidney Relations (Anterior)

• Right kidney: suprarenal gland, duodenum, liver, colon, small intestine.
• Left kidney: suprarenal gland, spleen, pancreas, stomach, colon, and small intestine.

Kidney Relations (Posterior)

• Posterior relations of both kidneys: diaphragm, muscles of the posterior abdominal wall (psoas major, quadratus lumborum, transversus abdominis).

Kidney Coverings

• Fibrous capsule
• Perirenal fat
• Renal fascia
• Pararenal fat

Ureters

• Two muscular tubes that convey urine from the kidneys to the urinary bladder.
• Each ureter is approximately 25 to 30 cm long.
• Half of the ureter's course is within the abdomen, and the other half is within the pelvis.
• The ureters are a continuation of the renal pelvis.
• Three constrictions during the ureter's course: pelvi-ureteric junction, crossing the common iliac artery, and uretero-vesical junction.

Urinary Bladder

• A hollow, muscular organ that serves as a reservoir for urine.
• Located in the pelvic cavity, behind the pubic bones.
• Shaped like a three-sided pyramid.
• Capacity is 220cc, but can accommodate up to 500cc.
• Apex is behind the upper part of the symphysis pubis and is continuous with the median umbilical ligament.
• Base is directed posteriorly.
• The bladder has three surfaces (one superior and two inferolateral) and a base. Each surface and base are triangular.

Bladder Related Structures

• Ureters enter the superolateral angle of the bladder base
• The inferior angle of the bladder transitions to the urethra.
• The male urethra is continuous with the prostatic part of the urethra.
• The female urethra is continuous with the urethra

Male Urethra

• 20 cm long, divided into three parts.
• Prostatic part: 3 cm, widest, begins at the neck of the urinary bladder, and houses the ejaculatory ducts.
• Membranous part: 1 cm, narrowest and shortest, surrounded by a sphincter,
• Spongy part: 16 cm, longest, passes through the penis, and opens by the external urethral orifice.

Female Urethra

• Very short, approximately 4 cm long
• Begins at the neck of the bladder.
• Its upper part is surrounded by sphincter urethra.
• Shorter, wider, and more dilatable than the male urethra.