Digestive System
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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