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Digestive System. By: Isaías Quezada, Emely Rivera, Carlos Sandoval Per.5. Overview. The digestive system consists of the Alimentary canal: Mouth Pharynx Esophagus Stomach Small intestine Anal canal Accessory structures: Salivary glands Liver Gallbladder Pancreas.

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Digestive System

By: Isaías Quezada, Emely Rivera, Carlos Sandoval


  • The digestive system consists of the Alimentary canal:
  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Anal canal
  • Accessory structures:
  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas
Structure of the Alimentary Canal’s Walls
  • Its' walls consist of four distinct layers that are developed to different degrees from region to region. Certain regions are specialized for certain functions. These layers are:
  • Mucosa
  • Submucosa
  • Muscular Layer
  • Serosa
  • formed of surface epithelium, lamina propria(connective tissue), and a small amount of smooth muscle
  • Function are protection, secretion, and absorption
  • Contains loose connective tissue, glands, blood vessels, lymphatic vessels, and nerves
  • Function is to nourish surrounding tissues and carry away any absorbed materials
Muscular Layer
  • consists of two coats of smooth muscle tissue arranged in circular and longitudinal groups
  • Provides movement of the tube and its contents
  • outer covering of the tube and comprised of visceral peritoneum, which is formed of epithelium on the outside and connective tissue beneath
  • Its function is both protection and lubrication
Types of Movement
  • There are two main motor functions of the alimentary canal; mixing & propelling
Types of Movement: Mixing
  • Occurs when smooth muscles in small segments of the tube contract rhythmically
  • When the stomach is full, waves of muscular contractions move along its wall from one end to the other.
  • The waves occur every twenty seconds and they mix foods with the digestive juices that the mucosa secretes
Types of Movement: Propelling
  • a wave-like motion called peristalsis occurs
  • a ring of contraction appears in the wall of the tube, yet just ahead the muscular wall relaxes
  • This action begins when food expands the tube
  • First portion of alimentary canal
  • Receives food
  • Begins mechanical digestion
  • Breaks food into smaller pieces
  • Organ of sensory and speech
  • Lateral walls of mouth
  • Consist of outer layers of skin
  • Pads of subcutaneous fat
  • Muscles that help with expressions and chewing
  • Moist inner layers moist, stratified squamious epithelium
  • Mobile structures surrounding mouth
  • Contain skeletal muscle
  • Judges temperatures and texture of food
  • Reddish color comes from amount of blood cells
  • External borders mark boundaries between skin of face and mucous membrane that lines in alimentary canal
  • Muscular organ rest on the bottom of the mouth
  • Covered by mucous membrane
  • Connected by midline to the floor by membranous fold, lingual frenulum
  • Composed of skeletal muscle fibers that run in several directions
  • Papillae
  • Root held by hyoid bone
  • Posterior covered in lingual tonsils
  • Roof of oral cavity
  • Hard anterior , soft posterior
  • Hard palate formed by palatine processes of maxillary
  • soft palate forms a muscular arch
  • Uvula
  • Muscles here help with swallowing
  • Palatine tonsils
  • Pharyngeal tonsils.
  • Hardest structures in body
  • Not considered part of the skeletal system
  • Develop in sockets in alveolar process of mandibular and maxillary bones
  • Permanent teeth come at about six years old
  • They break food into smaller particles, thus beginning the mechanical process
  • Helps mix food with saliva
Salivary Glands
  • Secretes saliva
  • minor glands are found on mucosa of the mouth
  • Constantly secreting fluid to keep mouth moist
  • There are 3 pairs of major glands, parotid, submandibular, sublingual
  • Secretory cells within the glands, Serous, and Mucous cells
  • Serous cells contain salivary amylase.
  • Enzymes split starch and glycogen molecules, they then become disaccharides
  • This begins chemical digestion
  • Mucous cells secrete mucus
  • Glands have parasympathetic and sympathetic nerves
  • Connects nasal and oral cavity with larynx and esophogus


  • Located: superior to the soft palate
  • Communicates with the nasal cavity and provides a passageway for air during breathing


  • Located: posterior to the mouth
  • Passageway from the mouth for air moving to and from the nasal cavity
Pharynx (continued)


  • Located: inferior to the oropharynx
  • Extends from the upper boarder of the….downward to the lower boarder of the cyroid cartilage of the larynx and is a passageway to the esophagus
  • Straight, collapsible tube that is about 25 cm. long
  • Provides a passageway for food
Cardiac Sphincter
  • Remain contracted
  • Close entrance to the stomach
  • Prevents regurgitation
Parts of the Stomach: Cardiac Region
  • A small are near the esophageal opening, or cardia
  • This is where the contents of the esophagus empty into the stomach
Parts of the Stomach: Fundic Region
  • Serves as a temporary storage area and sometimes fills with swallowed air
  • This produces a gastric air bubble which may be used as a landmark on a radiograph of the abdomen
Parts of the Stomach: Body Region
  • The main portion of the stomach and located between the fundic and pyloric portions
  • The main chamber for containing food
Parts of the Stomach: Pyloric Region
  • Funnel-shaped
  • Shape narrows and becomes the pyloric canal as it approaches the small intestine
  • At the end, the circular layer of fibers in its muscular wall thickens and forms the muscle Pyloric Sphincter, which acts as a valve that controls gastric emptying
Gastric Secretions
  • The stomach’s mucous membrane is studded with gastric pits, located at the ends of tubular gastric glands
  • Their structure and composition of their secretion vary in different parts of the stomach
  • All gastric glands generally contain 3 types of secretory cells
Secretory Cells
  • Mucous Cells: found in the necks of the glands near the openings and is responsible for lining the stomach from digestive juices
  • Chief Cells: also known as peptic cells are a key component of gastric juices
  • Parietal Cells: also known as oxyntic cells. When the chief cells secrete enzymes and parietal cells release a hydrochloric acid solution, they form the gastric juices
  • Endocrine Gland/exocrine function
  • Secretes pancreatic juices
Pancreas (structure)
  • Located posterior to parietal peritoneum
  • Pancreatic acinar cells: produce pancreatic cells
  • Aclai: clusters around tiny tubes which release their secretions
  • Small tubes connect to pancreatic duct
  • Pancreatic duct connects with duodenum
  • A J-shaped pouch like organ in the abdominal cavity
  • It receives food from the esophagus, mixes it with gastric juices, initiates the digestion of proteins, carries on limited absorption, and transports food into small intestine
  • Divided into four sections;
  • Cardiac region
  • Fundic section region
  • Body regions
  • Pyloric regions
  • Largest gland in the body
  • Weights 3.2 – 3.7 pounds
  • Detoxifies blood
  • Creates bile for stomach
  • Stores vitamins, iron, simple sugar glucose
  • Converts ammonia to urea
  • Very Likely to get disease due to the mass of functions it carries out
  • Pear shaped
  • Stores conventrate bile
  • Stores any bile that is not used
  • Cholecystokinin causes the release of bile to small intestine
  • Cholestoral, bile salts, can create Gallstones
Small Intestine
  • A tubular organ that extends from the pyloric sphincter to the beginning of the large intestine
  • Recieves secretions from the pancreas and liver
  • Completes digestion of the nutrients in chym
  • Begins in the mouth
  • Parctially digested carbs travel to esophagus and then the stomach
  • Move to the small intestine where they are broken down by enzymes from the pancreas
  • Then absorbed into the blood stream
  • Fiber passes through undigested


  • Some digested in mouth and stomach
  • Mainly in the small intestine
  • Bile produced in liver is sent to gallbladder
  • Fatty acids combine with cholesterol and bile
  • Transported to veins of chest and the blood carries fat to be stored in adipose tissue
macromolecules cont
  • Digested into amino acids
  • Begins in stomach with gastric juice
  • Potent enzymes from pancreas
  • Continues to the small intestine
  • Amino acids absorbd into the blood
Macromolecules (cont)
  • Shortest and most fixed portion of the small intestine
  • C-shaped
  • Recieves the partly digested food
  • Greater diameter
  • Thicker wall
  • More vascular
  • More active
  • Support absorption of carbohydrates and protiens
  • More lymph nodules
  • Higher bacterial population
  • Absorb chyme
Large Intestine
  • 1.5 meters long
  • Consists of cecum, colon, rectum, and anal canal
  • Begins in iliac region of pelvis
  • Joined together with small intestine
  • Continues across and down the abdominal cavity, and ends at the anus
  • Takes 16 hours to digest
  • Transports waste and re-absorption of water before it gets secreted.
  • Absorbs water and vitamins
  • Reduces Acidity
  • Produces antibodies
  • Tube like structure in lower abdominal cavity
  • Receives undigested food from small intestine
  • Absorbs fluids and salts that remain after intestinal digestion and absorption
  • Mixes the contents with mucus
  • Has a thick layer of mucous membrane
  • Layer of muscle that makes churning and rubbing movements
  • Removes water, salt, and nutrients that form stool
  • Muscles squeeze the contents through the intestine
  • Bacteria is found along the walls of the colon
  • 4 parts, descending, ascending, transverse, and sigmoid
  • Supported by peritoneum
  • 10 to 12 cm
  • Dilates towards the anus
  • Stores feces
  • Stretch receptors in walls tell when the body needs to defecate
  • When the rectum storage is full, the pressure pushes the feces to the anus
  • Body temperature can checked from rectum area
Anal Canal
  • 3-5 cm
  • Lubricates feces as it comes from rectum
  • Has muscular sphincter system that closes lumen
  • External anal sphincter surrounds anal canal and acts like a clamp. Similar to the puborectalis muscles that covers rectum from behind.
  • Both of which are voluntarily controlled
  • Internal anal sphincter relaxes so blood in anal cushions drain, which allows feces to go through