Respiratory System Functions

Chapter 22

• The major function of the respiratory system is to supply the body with oxygen and dispose of carbon dioxide.
• Respiration involves pulmonary ventilation (breathing), external respiration (gas exchange between lungs and blood), transport of respiratory gases, and internal respiration (gas exchange between blood and tissues).
• The respiratory zone, including structures like the respiratory bronchioles, alveolar ducts, and alveoli, is responsible for gas exchange.
• The nose functions to provide an airway for respiration, moisten and warm the entering air, filter and cleanse inspired air, serve as a resonating chamber for speech, and house the olfactory receptors.
• The pharynx is a passageway that connects the nasal cavity and mouth to the larynx and esophagus.
• The larynx functions to provide a patent airway, act as a switching mechanism to route air and food, and function in voice production.
• The nine cartilages of the larynx include the thyroid cartilage, cricoid cartilage, epiglottis, arytenoid cartilages (paired), cuneiform cartilages (paired), and corniculate cartilages (paired).
• The carina is the point where the trachea splits into the right and left main bronchi.
• Type II alveolar cells secrete surfactant.
• Infant respiratory distress syndrome is caused by a deficiency of surfactant in premature infants, leading to alveolar collapse.
• The pulmonary circulation supplies nutrients to the lungs.
• Pneumothorax is the presence of air in the pleural cavity, which can cause lung collapse.
• Serous fluid secreted by the pleural pleurae lubricates the space between the parietal and visceral pleurae, allowing the lungs to glide smoothly during breathing.
• Boyle's Law: Pressure and volume are inversely related (P1V1 = P2V2)
• Dalton's Law: The total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture.
• Henry's Law: When a mixture of gases is in contact with a liquid, each gas dissolves in the liquid in proportion to its partial pressure.
• The Bohr effect: Declining blood pH (acidosis) and increasing PCO2 cause hemoglobin to release oxygen, enhancing oxygen unloading where it is most needed.
• The most powerful stimulus for breathing in a healthy individual is an increase in the partial pressure of carbon dioxide (PCO2) in the blood.
• During inspiration, lung volume increases and pressure decreases and during expiration, lung volume decreases and pressure increases.
• The Hering-Breuer reflex is a protective mechanism that prevents overinflation of the lungs; it involves stretch receptors in the visceral pleurae and conducting airways.
• Tidal volume is the amount of air inhaled or exhaled with each breath under resting conditions (approximately 500 ml).
• Ciliated mucous epithelium in the nose traps debris and moves it posteriorly to the pharynx for swallowing.
• Vital capacity represents the total volume of exchangeable air.
• Types of Hypoxia include:
  • Hypoxic hypoxia (reduced oxygen in arterial blood)
  • Anemic hypoxia (poor O2 delivery due to too few RBCs or abnormal/ too little Hb)
  • Ischemic hypoxia (blood circulation is impaired)
  • Histotoxic hypoxia (body cells cannot use O2 even though adequate amounts are delivered)
• The effect of Po2, Pco2, acidity, temperature, and BPG on hemoglobin saturation with O2 includes:
  • Decreased Po2, increased Pco2, increased acidity, increased temperature, and increased BPG decrease hemoglobin saturation with O2 (rightward shift of the oxygen-hemoglobin dissociation curve).
• Carbon dioxide is transported in the blood in three forms: dissolved in plasma, bound to hemoglobin (carbaminohemoglobin), and as bicarbonate ions.
• Carbonic anhydrase is an enzyme that catalyzes the reversible reaction between carbon dioxide and water to form carbonic acid.
• Hypercapnia results in increased depth and rate of breathing.
• Increased pCO2 levels increase the activity of the phrenic nerve, which stimulates the diaphragm and increases ventilation.
• The uvula is a fleshy projection of the soft palate.

Chapter 23

• The general histology of the GI tract includes four basic layers: mucosa, submucosa, muscularis externa, and serosa (or adventitia).
• Saliva composition includes: water, electrolytes, mucus, enzymes (amylase, lysozyme), IgA antibodies, and metabolic wastes.
• Saliva functions to: cleanse the mouth, dissolve food chemicals for taste, moisten food, and begin the chemical breakdown of starch.
• The phases of deglutition (swallowing) are: the buccal phase (voluntary), the pharyngeal-esophageal phase (involuntary).
• The epithelium of the esophagus is stratified squamous epithelium.
• Peristalsis involves alternating waves of contraction and relaxation that propel food along the GI tract, while segmentation involves rhythmic local constrictions of the small intestine that mix food with digestive juices.
• The anatomy of the stomach includes regions such as the cardia, fundus, body, and pylorus and features like rugae, oblique layer.
• Gastric glands secrete hydrochloric acid (HCl), pepsinogen, mucus, intrinsic factor, and hormones (e.g., gastrin).
• Phases of gastric juice secretion include the cephalic phase (triggered by the sight, smell, taste, or thought of food), the gastric phase (stimulated by stomach distension and peptides), and the intestinal phase (brief stimulatory effect followed by inhibition).
• Liver functions include: bile production, detoxification, nutrient metabolism, storage of glycogen/vitamins/minerals, synthesis of plasma proteins, and removal of old or damaged red blood cells.
• Pancreatic enzymes include: amylase, lipases, nucleases, and proteases (e.g., trypsin, chymotrypsin, carboxypeptidase).
• Pancreatic secretion is regulated by hormones (secretin and cholecystokinin (CCK) and parasympathetic innervation.
• The hepatic portal circulation carries blood from the GI tract, spleen, and pancreas to the liver for processing.
• The hepatopancreatic ampulla (ampulla of Vater) is the bulb-like point in the wall of the duodenum where the bile duct and main pancreatic duct fuse.
• Bile is a yellow-green alkaline solution containing bile salts, bile pigments (bilirubin), cholesterol, neutral fats, phospholipids, and electrolytes.
• Hepatocytes produce bile, and bile functions to emulsify fats and facilitate fat and cholesterol absorption.
• The parts of the small intestine are the duodenum, jejunum, and ileum.
• Plicae circulares are deep, permanent folds in the mucosa and submucosa of the small intestine that increase surface area for absorption.
• Enterokinase (enteropeptidase) is an enzyme in the duodenal mucosa that converts trypsinogen to trypsin.
• Nutrient absorption occurs via active and passive transport mechanisms, including diffusion, facilitated diffusion, osmosis, active transport, and endocytosis.
• The majority of water is absorbed in the small intestine.
• Protein digestion begins in the stomach.
• Gastrin stimulates gastric secretion.
• Amylase digests carbohydrates.
• Chyme is the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.
• Proteins are denatured in the stomach by hydrochloric acid.
• The release of bicarbonate-rich pancreatic juice is triggered by secretin.
• Control of the internal anal sphincter is involuntary, while control of the external anal sphincter is voluntary.

Chapter 24

• The primary function of cellular respiration is to generate ATP by oxidizing organic molecules.
• Cholesterol helps stabilize the membrane and reduces fluidity.
• Gluconeogenesis is the process of forming new glucose from non-carbohydrate sources.
• Glycogenolysis is the breakdown of glycogen to glucose.
• Hormones of the absorptive stage of digestion include insulin, and during the post-absorptive stage, glucagon and epinephrine.