Respiratory & Digestive Systems

• These notes cover the respiratory and digestive systems, including anatomy, functions, and processes

The Respiratory System

• The diaphragm is essential for breathing; its contraction increases the thoracic cavity's size, facilitating air intake, while relaxation reduces it, leading to air expulsion
• The trachea, or windpipe, connects the larynx to the bronchi, and its cartilage rings are open posteriorly to allow the esophagus to expand during swallowing
• Alveoli are lung air pouches where oxygen is taken in during inhalation and carbon dioxide is expelled during exhalation, enabling gas exchange between air and blood
• Squamous type 1 alveolar cells facilitate rapid gas diffusion between air and blood, covering 95% of the alveolus surface area
• Great type 2 alveolar cells repair alveoli epithelium when type 1 cells are damaged and secrete pulmonary to prevent collapsing
• Alveolar macrophages, or dust cells, are the most numerous lung cells, keeping alveoli clear of debris through phagocytosis
• Bronchi are large tubes connecting the trachea to the lungs, directing airflow and facilitating oxygen intake and carbon dioxide expulsion
• Intercostal muscles support the diaphragm, contributing to thoracic cage enlargement and contraction and adding about 1/3 of air during ventilation
• The larynx primarily prevents food and drink from entering the airway and also functions as the voice box
• The epiglottis and vestibular folds work together to prevent food and drink from entering the airway
• The pleura membrane reduces friction, creates a pressure gradient to assist with lung inflation, and compartmentalizes to prevent infection spread
• Cellular respiration is a biochemical process where cells break down glucose to derive usable energy
• The respiratory system facilitates gas exchange, communication, olfaction, acid-base balance, blood pressure regulation, blood and lymph flow, platelet production, blood filtration, and abdominal content expulsion
• Oxygen is transported through the body via alveoli air sacs surrounded by blood vessels, where red blood cells pick up and deliver oxygen
• Hyperventilation involves increased pulmonary ventilation beyond metabolic demand
• Rate of breathing is regulated by the medulla oblongata

Respiratory Volumes

• Tidal volume: 500 mL of air inhaled and exhaled in one breath
• Residual volume: 1,300 mL of air remaining after maximum exhalation
• Expiratory reserve volume: 1,200 mL of air exhaled beyond tidal volume with maximum effort
• Vital capacity: total air volume inhaled and exhaled with maximum effort

Diaphragm Function

• During inspiration (breathing in), the diaphragm goes down to expand the lungs to receive more air
• During expulsion (breathing out), the diaphragm goes up to expel carbon dioxide
• Cilia are small finger-like projections in the nose that trap germs and debris from entering

The Digestive System

• The stomach primarily stores food, breaks it down into chyme, and passes it to the small intestine
• The liver's digestive function is to secrete bile; it is the body's largest gland
• The gallbladder concentrates bile by absorbing water and electrolytes
• The pancreas secretes insulin, glucagon, pancreatic amylase, and pancreatic lipase
• Gastric juices are mainly composed of water, hydrochloric acid, and pepsin, crucial for digestion in the stomach
• Mechanical and chemical digestion both begin in the mouth
• Digestive enzymes are produced by salivary glands, stomach, pancreas, and small intestine
• They break down polysaccharides into monosaccharides, proteins into amino acids, fats into monoglycerides and fatty acids, and nucleic acids into nucleotides
• The liver produces bile
• The small intestine is divided into the duodenum, jejunum, and ileum

Small Intestine Sections

• The duodenum receives stomach contents, pancreatic juice, and bile
• The jejunum is where most digestion and nutrient absorption occurs
• The ileum regulates the passage of food residue into the large intestine
• Villi increases the absorptive surface area

Digestion Process

• Mouth: mechanical and chemical digestion, bolus formation, and taste occur
• Pharynx: acts as a passageway and aids in swallowing
• Esophagus: Peristalsis moves food
• Mucus aids food lubrication and the swallowing process
• The pharynx is shared by both the respiratory and digestive systems
• Food Breakdown:
  • Ingestion: Food enters mouth and gets chewed
  • Saliva: Break down carbohydrates
  • Mouth:
  • Esophagus:
    • Swallowing
    • Peristalsis
  • Stomach:
    • Mixing of chyme and gastric juice
    • Digestion
  • Small intestine:
    • Duodenum: chyme mixes with bile
    • Digestion
    • Absorption
  • Large intestine:
    • Absorption: absorb water
    • Waste formation: turns into solid waste
  • Rectum:
    • Storage: stool stored in rectum until eliminated
    • Defecation: elimination of stool
• Proteins are broken down into amino acids by enzymes like pepsin and pancreatic enzymes
• Lower esophageal sphincter prevents stomach contents from flowing back up the esophagus.
• Pyloric sphincter controls passage of chyme from stomach to small intestine.
• Internal anal sphincter involuntary muscle helps maintain fecal continence.
• External anal sphincter voluntary muscle, allows control of bowel movements.
• Sphincter of oddi controls flow of bile and pancreatic secretion into the duodenum
• The stomach has a pH that ranges from 1.5-3.5 which is very acidic
• Eating food with fat stimulates the gallbladder to release bile
• Glucose is stored in the liver in the form of glycogen
• Gastric and Ghrelin hormone stimulates stomach acid release, however Ghrelin isn't released after a stomach reduction