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

Learn about the complex of organs and tissues that facilitate the exchange of oxygen and carbon dioxide in the body, including breathing, oxygen absorption, and carbon dioxide discharge.