Human Anatomy: Urethra Quiz

Contact Information

• Abdeslem El Idrissi, PhD
• Center for Developmental Neuroscience
• City University of New York
• College of Staten Island
• [email protected]

System Summaries

• Urinary System
• Reproductive System
• Digestive System
• Lymphatic System
• Sensory Organs

Urinary System Histology

• Introduction
  • The urinary system removes waste products from the body
  • Kidneys regulate blood volume, pressure, and composition
  • The urinary system is closely associated with the reproductive system, sharing embryonic development and adult anatomical relationships

Functions of the Kidneys

• Filter blood and excrete toxic metabolic wastes
• Regulate blood volume, pressure, and osmolarity
• Regulate electrolytes and acid-base balance
• Secrete erythropoietin for red blood cell production
• Help regulate calcium levels through calcitriol synthesis
• Clear hormones from the blood
• Detoxify free radicals

Nitrogenous Wastes

• Waste: any substance useless or excessive to the body
• Metabolic waste: waste produced by the body
• Urea formation: proteins → amino acids → ammonia → urea
• Uric acid: product of nucleic acid catabolism
• Creatinine: product of creatine phosphate catabolism
• Blood urea nitrogen (BUN): level of nitrogenous waste in blood
  • Normal: 10-20 mg/dL
  • Elevated BUN (azotemia): possible renal insufficiency
  • Uremia: syndrome due to nitrogenous waste toxicity (diarrhea, vomiting, dyspnea, cardiac arrhythmia)

Excretion

• Excretion: separating and eliminating wastes from body fluids
• Four body systems involved:
  • Respiratory system: removes small amounts of gases and water
  • Integumentary system: removes water, inorganic salts, lactic acid, and urea in sweat
  • Digestive system: removes water, salts, lipids, bile pigments, cholesterol, and other metabolic wastes
  • Urinary system: removes many metabolic wastes, toxins, drugs, hormones, salts, and water

Retroperitoneal Position of the Kidney

• The kidneys are located behind the peritoneum
• Various organs and structures surround the kidneys, as shown in a diagram.

Gross Anatomy of the Kidney

• Shape and Size: roughly the size of a bar of bath soap, with a convex lateral surface and a concave medial surface (hilum)
  • The hilum receives renal nerves, blood vessels, lymphatics, and ureter.
• Three Protective Coverings:
  • Renal fascia: immediately deep to parietal peritoneum, binds kidney to abdominal wall
  • Perirenal fat capsule: cushions kidney and holds it in place
  • Fibrous capsule: surrounds kidney, protecting it from trauma and infection

Two Zones of Renal Parenchyma

• Outer renal cortex
• Inner renal medulla containing renal columns and pyramids

Kidney Anatomy

• Renal columns: extensions of cortex projecting inward toward sinus
• Renal pyramids (6-10): broad base toward cortex, renal papilla toward sinus
• Lobe of kidney: one pyramid plus its overlying cortex
• Minor calyx: each pyramid's papilla cup, collecting urine
• Major calyx: formed by converging minor calyces
• Renal pelvis: formed by major calyces; a tubular continuation into the ureter, draining urine to the urinary bladder

Renal Circulation

• Blood flow to and from kidneys, including arteries (renal, segmental, interlobar, arcuate) and veins (segmental, interlobar, arcuate, renal)

Microcirculation of the Kidney

• Describes the flow of blood through the cortical and juxtamedullary nephrons, including the glomerulus, PCT, DCT, nephron loop, and collecting ducts.

The Renal Corpuscle

• Vascular pole: where afferent arteriole enters and efferent arteriole leaves
• Urinary pole: where renal tubule begins
• Glomerular capsule: parietal and visceral layers, podocytes, filtration slits, Bowman's capsule
• Glomerulus: capillaries for filtration

Microscopic Anatomy of the Nephron

• Renal corpuscle, glomerulus, and its associated capsule
• Tubules (proximal convoluted tubule, nephron loop, distal convoluted tubule)
• Collecting ducts

Renal Cortex (LM: Medium Magnification)

Renal Corpuscle (LM: High Magnification)

Renal Medulla (LM: Medium Magnification)

Renal Medulla (Longitudinal Section)

Structure of the Glomerulus

• Podocytes, filtration slits, and blood vessels within the glomerulus

The Glomerular Filtration Membrane

• Three layers (endothelium, basement membrane, podocytes) through which fluid passes, excluding cells and large proteins

Podocytes (SEM: High Magnification)

Podocytes (TEM: High Magnification)

Basic Stages of Urine Formation

• Glomerular Filtration, Tubular Reabsorption, Tubular Secretion, Water Conservation

The Proximal Convoluted Tubule

• Reclaims about 65% of glomerular filtrate.
• Active transport of substances into the filtrate.
• High microvilli and mitochondria.

Proximal Convoluted Tubule (TEM: Low Magnification)

The Distal Convoluted Tubule and Collecting Duct

• Reabsorption of water and salt is regulated by several hormones (aldosterone, atrial natriuretic peptide, ADH, and parathyroid hormone).
• Fine-tuning of urine composition

Distal Convoluted Tubule (TEM: Low Magnification)

Urine Storage and Elimination

• Urine produced continuously but eliminates episodically.
• Storage apparatus and neural controls release urine at desired intervals

The Ureters

• Retroperitoneal muscular tubes connecting each kidney to the urinary bladder.
• 25 cm long; pass posterior to bladder and enters from below.
• Flap of mucosa at entrance, acting as a valve

The Ureters (Continued)

• Three layers: adventitia, muscularis (smooth muscle layers), mucosa (transitional epithelium)
• Peristaltic waves move urine.
• Narrow lumen—prone to obstruction (kidney stones)

Ureter (LM: Low Magnification)

Ureter (LM: High Magnification)

The Urinary Bladder

• Muscular sac in the pelvic cavity.
• Covered by parietal peritoneum superiorly.
• Three layers : muscularis (detrusor), mucosa (transitional epithelium).
• Umbrella cells to protect mucosa from urine.

The Urinary Bladder 2

• Trigone: triangular area on the floor with openings for ureters and urethra
• Capacity: moderate fullness is 500 ml, maximum is 700-800 ml
• Highly distensible, expanding as it fills
• Rugae flatten upon filling, epithelium thins

The Urinary Bladder 3

• Location and structure in both female and male anatomy

Urinary Bladder Histology

Urinary Bladder (LM: Low Magnification)

Urinary Bladder (LM: High Magnification)

The Urethra

• Tube conveying urine outside the body
• Female urethra: 3-4 cm long, orifice between vaginal and clitoral orifices.
• External urethral sphincter (skeletal muscle).

The Female Urethra

The Urethra 2

• Male urethra is 18 cm long.
• Three regions:
  • Prostatic urethra
  • Membranous urethra
  • Spongy (penile) urethra
• Internal and external urethral sphincters, thickening of detrusor muscle

The Male Urethra

Test your knowledge of the human urethra with this quiz, focusing on its anatomy and function. You will answer questions about the lengths of the male and female urethra, the components of the urethral sphincter, and the regions of the urethra itself.