Respiratory System Functions

Respiratory System

• The respiratory system is a complex of organs and tissues that exchange blood carbon dioxide (CO2) with air oxygen (O2).
• Its functions include:
  • Breathing, which involves inhaling and exhaling air in the body
  • Absorbing oxygen from the air to produce energy
  • Discharging carbon dioxide, a byproduct of the process

Respiratory Epithelium

• The respiratory epithelium is a tissue that lines the respiratory system
• Its roles include:
  • Serving as a protective barrier
  • Providing moisture

Parts of the Respiratory System

Upper Respiratory Tract

• Includes the nose, mouth, and the beginning of the trachea

Lower Respiratory Tract

• Includes the trachea, bronchi, bronchioles, and lungs
• The trachea connects the throat to the bronchi
• The bronchi divide into two tubes, which then branch into smaller tubes called bronchioles, ending in pulmonary alveoli

Lungs

• The lungs include the bronchial tree, which branches off from the bronchi into smaller and smaller air tubes, each ending in a pulmonary alveolus

Nasal Cavities

• The nasal cavities are lined by a ciliated pseudostratified columnar epithelium containing olfactory cells
• The mucosa of the nasal cavities contains:
  • Olfactory nerves
  • Olfactory glands that secrete a proteinaceous substance, keeping the surface moist and trapping aromatic substances

Pharynx

• The pharynx contains mucous glands and is lined by stratified squamous epithelium, continuous with the epithelium at the proximal end of the larynx

Cell Types in the Respiratory System Epithelium

• There are eight different cell types in the respiratory system epithelium:
  • Ciliated cells
  • Goblet (mucous) cells
  • Basal (short) cells
  • Clara cells (bronchiolar epithelial cells)
  • Brush cells
  • Dense core granule cells (small granule cells, neuroendocrine cells)
  • Serous cells
  • Intermediate cells

Histology of the Alveolar Region

• Five major cell types are present in the alveolar region:
  • Alveolar Type I cells (squamous alveolar epithelial cells)
  • Alveolar Type II cells (great alveolar cells, granular pneumocytes)
  • Capillary endothelial cells
  • Alveolar macrophages
  • Interstitial cells

Urinary System

• The urinary system helps the body eliminate liquid waste (urea) and regulate chemicals, such as potassium and sodium, and water balance
• The kidneys produce erythropoietin, which controls red blood cell production in the bone marrow
• The kidneys also regulate blood pressure, acid-base balance, and conserve fluids

Components of the Urinary System

• The kidneys, ureters, urinary bladder, and urethra are the main components of the urinary system
• The processes can be divided into two steps:
  • Filtration: glomeruli of the kidney
  • Selective resorption and excretion: tubular system of the kidney

Kidney Structure

• The kidney is composed of an outer cortex and inner medulla
• The medulla contains multiple cone-shaped lobes, known as medullary pyramids
• The urinary lobes are fused in the cortex

Nephron

• The nephron is the structural and functional unit of the kidney
• It includes:
  • Renal corpuscle
  • Proximal convoluted tubule
  • Loop of Henle
  • Distal convoluted tubule

Glomerulus

• The glomerulus is a capillary bundle that receives its blood supply from an afferent arteriole of the renal circulation
• Inside the glomerulus is Bowman's capsule, which has two layers:
  • The visceral layer, in contact with the glomerulus, composed of specialized epithelial cells known as podocytes
  • The parietal layer, the outer layer, composed of simple squamous epithelial cells

Renal Pelvis and Ureter

• Numerous collecting ducts merge into the renal pelvis, which then becomes the ureter
• The ureter is a muscular tube, composed of an inner longitudinal layer and an outer circular layer
• The lumen of the ureter is covered by transitional epithelium

Urinary Bladder

• The urinary bladder stores urine as it is produced and releases it from the body
• It is lined with transitional epithelium that stretches as the bladder fills
• The wall contains smooth muscle that contracts to expel urine

Urethra

• The urethra carries urine away from the bladder to the outside of the body
• The epithelium changes from transitional to stratified or pseudostratified columnar in the urethra, and to stratified squamous in the distal end of the urethra