Exercise 9-11

• Digestive system

  Resides within the body cavity head and neck
• Digestive system

  • Concerned with both mechanical and chemical processing of the food
  • Organs positioned in series to form a long digestive tract (alimentary or gastrointestinal tract)
  • Each organ is specifically constructed and adapted for different stages in the digestive process
• Mechanical processing

  Involves breaking large particles of food to smaller ones enough for the enzymes to act upon and start the chemical process of digestion
• Chemical digestion

  1. Includes breakage of chemical bonds of foods such as the polysaccharides, proteins and fats and lipids

  2. The final products of this digestive process are absorbed by the walls of the tract
• Small Intestine

  Major absorption occurs in the walls
• Large Intestine

  • Where water is absorbed
  • Receives undigested food residues
• Accessory organs for digestion

  • Liver
  • Pancreas
• Liver

  • Secretes bile which emulsifies the fats, a preparatory process necessary for fat digestion
  • Secretes a hormone, cholecystokinin, that signals the gallbladder to release the bile content into the duodenum
• Pancreas

  • Supplies the small intestine with its digestive zymogens
  • Zymogens are activated in the intestine converting these substances to active enzymes for protein digestion
  • Secretes pancreatic lipase that finally digests the emulsified fats
• Mouth/Buccal (Oral) cavity

  • Divided into the vestibule and mouth cavity proper by the gums and teeth
  • Vestibule is surrounded by the lips and cheeks
  • Mouth cavity proper contains the tongue and the teeth
• Frenulum linguale

  A fold of tissue that ties the tongue to the floor of the mouth
• Tongue

  • Made up of striated skeletal muscle covered with mucous membrane
  • Has numerous papillae, many of which are horny and toothlike on its rough outer surface
• Palate

  • The hard palate at the roof of the buccal cavity is made up of 7-8 transverse ridges
  • Posterior to the hard palate is the soft palate
• Types of teeth

  • Incisors
  • Canines
  • Premolars
  • Molars
• Salivary glands

  • Parotid gland
  • Submaxillary gland
  • Sublingual gland
  • Molar glands
  • Infraorbital glands
• Pharynx

  • A common tube that receives respiratory gasses from the nasal cavity and food the oral cavity
  • Divisible into three parts: Nasopharynx, Oropharynx, Laryngopharynx
• Esophagus

  A muscular tube that extends from the laryngopharynx to the stomach, traversing the neck and thoracic cavity to reach the stomach within the abdominal cavity
• Stomach


  • Fundus - the pouch that rises above the entrance of the esophagus
  • Central area - the body of the stomach
  • Pyloric region - lies posterior to the body, ends at the pylorus (a sphincter muscle)
  • Greater curvature - the left convex surface
  • Lesser curvature - the right concave surface
  • Rugae - prominent longitudinal folds in the inner stomach wall
• Duodenum


  The first part of the small intestine where the pyloric region of the stomach opens into
• Parts of the small intestine

  • Duodenum
  • Jejunum
  • Ileum
• Villi


  Tiny folds which serve to increase the surface area for absorption, making the inner lining of the small intestine velvety to touch
• Mesentery proper

  Supports the small intestine, attached to the dorsal body wall over a small area in the region of the duodenum
• Large intestine

  • Begins at the ileocecal valve, considerably larger in diameter than the small intestine
  • Cecum - the blind sac that marks the beginning of the colon, short and vestigial
  • Ascending colon - short
  • Transverse colon - short
  • Descending colon - merges imperceptibly with the rectum which ends at the anus
• Mesocolon

  The mesentery attaching the colon to the dorsal body wall
• Accessory organs of the digestive system

  • Salivary glands
  • Pancreas
  • Liver
• Salivary glands

  Responsible for the secretion of ptyalin (salivary amylase) which chemically breaks down polysaccharides into disaccharides, maltose
• Pancreas

  Yellowish, fleshy structure lying on the gastrohepatoduodenal mesentery of lesser omentum next to the descending duodenum
• Liver

  • The largest visceral organ, reddish-brown in color, found fitting against the posterior surface of the diaphragm, divided into 5 lobes
• One of the major transitions in vertebrate evolution is the change from water breathing to air breathing
• Primary respiratory organs


  • Gills
  • Lungs
• Organs for cutaneous respiration


  • Gas bladders
  • Skin
• Respiration


  1. Ventilation of the lungs (external respiration or breathing)
  2. The exchange of gasses between air and blood and between blood and tissue fluid (internal respiration)
  3. The use of oxygen in cellular metabolism (cellular respiration)
• Principal organs of the respiratory system


  • Nose
  • Pharynx (Nasopharynx, Laryngopharynx)
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Upper respiratory tract


  The airway, from the nose through the pharynx
• Nose


  • Warms, cleanses, and humidifies inhaled air
  • Detects odors in the airstream
• Larynx


  Also known as the voice box, a chamber with cartilaginous walls, leading from glottis to the lungs
• Cartilages of the larynx


  • Epiglottis
  • Thyroid cartilage
  • Cricoid cartilage
  • Arytenoid cartilage
  • Vocal cords
• Trachea


  A long, median, tube connecting the larynx to the lungs, lies ventral to the esophagus, with walls supported by cartilaginous C-shaped rings which are incomplete on the dorsal side
• Bronchi


  • Primary bronchi
  • Secondary bronchi
  • Tertiary bronchi
  • Terminal bronchioles
• Lungs


  • Cone-shaped, with the base resting on the diaphragm and the apex extending superiorly, slightly above the clavicle
  • There are two lungs - right lung and left lung
  • Each lung is subdivided into three lobes - anterior lobe, middle lobe, posterior lobe
  • The right lung has its posterior lobe subdivided into lobules