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• Ingestion


  The process of taking in food usually at the point where the gastrointestinal tract begins
• Digestion

  The process of breaking down the ingested food into smaller molecules for an efficient absorption of nutrients
• Types of mechanical digestion

  • Mechanical digestion
  • Chemical digestion
• Mechanical digestion


  • Involves the physical breakdown of food molecules
  • Increases the surface area of food available for digestion
  • Mechanisms involve chewing, biting, and churning
• Chemical digestion


  • Involves the chemical breakdown of food molecules
  • Utilizes enzymes that are specific for food molecules
  • Makes the process of absorption more efficient
• Secretion

  Takes place as digestive organs synthesize and release enzymes that will facilitate the chemical digestion
• Absorption


  Takes place as the ingested food is completely digested for transport to other tissues of the body
• Mouth cavity


  • Site for both mechanical and chemical digestion
  • Hard and soft palates separate the oral and nasal cavities
  • Tongue is a muscular organ for tactility and gustation
  • Teeth physically breakdown the food
  • Humans have 32 teeth
• Pharynx


  • Tube that connects the mouth and esophagus
  • Nasopharynx is the passageway for air
  • Oropharynx is a food and air passage
  • Laryngopharynx is the passageway for food
• Epiglottis


  • Flap of tissue found in the throat behind tongue
  • Moves down during deglutition after being pushed by food
  • Blocks the trachea if pushed down by food and water
  • Prevents the entry of food into the respiratory tract
• Esophagus


  • Long tube that connects mouth with stomach
  • Sphincters prevent food backflow
  • Peristalsis or involuntary muscle contractions push food
• Stomach


  • Hollow, curved, muscular organ
  • Site for both the storage and digestion of food
  • Has rugae, which allows stretching to accommodate food
  • Consists of the cardia, fundus, and pylorus

  
• Gastric secretions


  • Gastric amylase
  • Gastric lipase
  • Hydrochloric acid
  • Pepsin
• Gastric amylase


  Digests complex carbohydrates into smaller disaccharides
• Gastric lipase


  Initiates the digestion of dietary fats into smaller fatty acid chains
• Hydrochloric acid


  Helps kill the bacterials cells present in food and activates the pepsinogen
• Pepsin


  Acts as a protease by initiating protein digestion
• Small intestine


  • 20 foot-long, site of most chemical digestion
  • Duodenum is the site where most chemical digestion occurs
  • Receives the enzymes from liver and pancreas
  • Jejunum and ileum are sites of digestion and nutrient absorption

  
• Duodenal secretions


  • Maltase
  • Lactase
  • Maltase
  • Peptidase
  • Nucleosidase
• Maltase


  Digests maltose into monosaccharides (two glucose molecules)
• Lactase


  Digests lactose into monosaccharides (glucose and galactose molecules)
• Maltase


  Digests sucrose into monosaccharides (glucose and fructose molecules)
• Peptidase


  Digests peptides chains into their constituent amino acids
• Nucleosidase


  Digests nucleotides into component phosphates, sugars, and bases
• Large intestine


  • 3 foot-long, has little to no digestive function
  • Site of absorption of vitamins and water
  • Primary secretion is mucus
  • Has crypts similar to the small intestine

  
• Rectum and anus


  • Rectum is the storage site for feces before defecation
  • Rectum can also absorb water
  • Anal columns and sphincters help regulate defecation
• Accessory organs


  • Salivary glands
  • Liver
  • Pancreas
  • Gallbladder
• Salivary glands


  • Secrete saliva that can lubricate and moisten the food
  • Saliva contains amylase that initiates the carbohydrate digestion in mouth
  • Consist of the parotid, sublingual, and submandibular glands
• Digestive enzymes


  • Bile
  • Amylase
  • Trypsin
  • Lipase
  • Nuclease
• Bile


  Responsible for starch digestion
• Amylase


  Responsible for protein digestion
• Trypsin


  Responsible for lipid digestion
• Lipase


  Performs nucleic acid digestion
• Nuclease


  Performs nucleic acid digestion
• The digestive system acts on breaking down ingested food and absorbing nutrients for distribution to the cells of the body
• Digestion or the process of breaking down food through mechanical and chemical means
• Its primary components are the digestive tract and the accessory organs

  
• The digestive tract includes the mouth, esophagus, stomach, small intestine, and large intestine. The ingested food passes through this long tube to subject to both mechanical and chemical digestion

  
• The accessory organs are the salivary glands, liver, pancreas, and gallbladder. These structures support the digestive function by secreting enzymes that facilitate the chemical digestion
• Major functions of the urinary system

  • Excretion
  • Regulation of blood volume and pressure
  • Regulation of the concentration of solutes in the blood
  • Regulation of extracellular fluid pH
  • Regulation of red blood cell synthesis
  • Regulation of vitamin D synthesis