Practical 3

• Major Organs of Digestive system are categorized into either gastrointestinal (GI) tract organs, or accessory organs
• gastrointestinal (GI) tract organs : organs with a continuous lumen between mouth and anus
• Accessory Organs : aid the function of the GI tract
• Organs of GI Tract

  Tongue

  • Site of ingestion
• Tongue

  • Salivary glands release their product, saliva, which contains enzymes that aid in chemical digestion
• Organs of GI Tract

  Tongue

  Teeth and tongue are involved in mastication, or chewing
• Organs of GI Tract

  Pharynx

  • Cavity behind the nose, mouth, larynx, connects them to esophagus.
  • Walls of pharynx composed of skeletal muscle and are crucial for proper swallowing
• Organs of GI Tract

  Esophagus

  • Tube carries food from pharynx to stomach
  • Upper esophagus has skeletal muscle in walls while lower has smooth muscle
  • Middle esophagus is a point of transition between the two
• Organs of GI Tract

  Stomach

  • Primary site of mechanical food breakdown
  • Gastroesophageal junction houses the lower esophageal spincter, which prevents stomach contents from refluxing into esophagus
  • Area around lower esophageal spincter is the cardia
• Organs of GI Tract

  Stomach

  • Rounded region superior to cardia is the fundus
  • The Pylorus funnels stomach contents toward the gastroduodental junction, and the pyloric spincter keeps stomach contents from entering duodenum until appropriate time
  • Between funus and pylorus lies the body
• Organs of GI Tract

  Stomach

  Two sphincters result from a localized thickening of circular layer of muscularis externa
• Organs of GI Tract

  Stomach

  • Contraction of three muscularis externa pulverize food, and mix it with gastric enzymes that aid chemical digestion
  • Rugae - extensive folds of intestinal mucosa and submucosa allow stomach to expand without rupturing, and also increase surface area for acid nd enzyme release
• Organs of GI Tract

  Small Intestine

  • Begins at gastroduodenal junction, which houses pyloric sphincter, a thickened region of circular muscle prevents stomach contents from leaking into intestine until fully processed
  • Small intestine has three region, duodenum, jejunum and ileum. Duodenum is near stomach, ileum is near large intestine and jejunum is between them.
• Stomach :)

  A) Body

  B) Fundus

  C) Pylorus

  D) Pyloric

  E) Lower

  F) Duodenum

  G) Cardia

  
• Organs of GI tract

  A) Stomach

  B) Large Intestine

  C) Small Intestine

  
• Organs of GI Tract

  Three accessory structures - liver, gallbladder, and pancreas

  • secrete products into duodenum, allowing small intestine to carry out its primary functions — chemical digestion and nutrient absorption
• Three accesory structures of GI Tract

  A) Liver

  B) Gallbladder

  C) Pancreas

  
• Organs of GI Tract

  Large Intestine

  Ileum of small intestine deposits its contents into large intestine at ileocecal junction
• Organs of GI Tract

  Large Intestine

  Six defined regions :

  1. Cecum
  2. ascending colon
  3. transverse colon
  4. descending colon
  5. sigmoid colon
  6. rectum
• Organs of GI Tract

  Large Intestine

  • reclaim water from feces, some specialized nutrient absorption that occurs
• Organs of GI Tract

  Large Intestine

  Projecting from cecum is appendix, which stores beneficial bacteria that colonize large intestine, allowing us to repopulate those bacteria following intestinal illness
• Organs of GI Tract

  Anal Canal

  • Point of fecal excretion from body. Feces dry and abrasive, so stratified squamous epithelium of anal canal provides extra protection against damage to lining
• Accessory structures of digestive system

  Teeth

  teeth involved in mastication of food in mouth, which decreases size of food particles
• Accessory structures of digestive system

  Tongue

  Moves food around in mouth to enhance chewing. Also aids in swallowing
• Accessory structures of digestive system

  Salivary glands

  Saliva, produced, contains enzymes that are mixed with food during mastication and aid in chemical digestion of nutrients
• Accessory structures of digestive system

  Teeth

  • teeth built for strength
  • crown of tooth is part you can see
  • root is embedded into bone and gingiva (your gum)
• Accessory structures of digestive system

  Teeth

  • outer layer of crown called enamel. This acellular mineralized material is not susceptible to decomposition like other tissue
  • can be degraded and weakened by acids,
  • once eroded, cannot be replaced
• Accessory structures of digestive system

  Teeth

  • Supporting the enamel is dentin. Acellular substance is vaguely bone - like, though it is denser and harder.
  • Produced by live cells called odontoblast, found on inner dentin surface, just outside dental pulp
  • Dental pump composed of loose connective tissue that supplied by branches of alveolar nerves and blood vessels
• Accessory structures of digestive system

  Teeth

  Dental pump involved in sensory detection, as well as delivery of nurtients to odontoblasts
• Accessory structures of digestive system

  Teeth

  Unlike crown, root of tooth is not enclosed in enamel, rather a substance called cementum

  Cementum important because periodontal ligments an attachment site so they can fasten root of tooth into alveolar
• Accessory structures of digestive system

  Teeth

  • Cellular cementum is involved in root modeling, happens as teeth move around
  • At open surface, alveolar bone is covered in gingival epithelium, keratinized stratified squamous epithelium, and is anchored to bone by connective tissue lamina properia
  • Gingival lamina propria rich in immune cells, since frequently damanged during chewing
• Accessory structures of digestive system

  Teeth

  Human have 20 baby teeth and 32 permanent teeth, 16 maxillary (upper) and 16 mandibular (lower)
• Accessory structures of digestive system

  Teeth

  Incisors : useful in cutting bots of food and used as tool when manipulating small objects

  Canines : help tear up food

  Premolar and molar : broad surfaces that allow us to grind foo
• Large Intestine

  A) Cecum

  B) Ascending

  C) Transverse

  D) Descending

  E) Sigmoid

  F) Rectum

  G) Anal canal

  
• Tooth :p

  A) Crown

  B) Root

  C) enamel

  D) dentin

  E) pulp

  F) gum

  G) Cementum

  H) Periodontal ligment

  
• Set of teeth

  A) Maxillary

  B) mandibular

  C) incisor

  D) incisor

  E) canine

  F) premolar

  G) premolar

  H) molar

  I) molar

  J) molar

  
• Accessory structures of digestive system

  Tongue

  • Tongue plays central role in chewing and swallowing
  • During chewing, tongue moves food around so teeth may be used to grind and cut it into pieces
  • particulary true of filiform papillae, found all over tongue
  • other papillae (vallate,foliate and fungiform) important as they are lined by taste buds
• Accessory structures of digestive system

  Tongue

  • large number of minor salivary glands. Gustatory gland specifically associated with posterior tongue. As group, minor salivary glands in tongue called lingual salivary glands
  • Tongue has abundant skeletal muscle, can voluntarily shift food about and swallow on demand
• Accessory structures of digestive system

  Major Salivary glands

  • Encapsulated organs with defined ducts that deliver their products to oral cavity
  • Produces slightly acidic saliva, roch in amylases, which chemically digest carbohydrates, as well as some lipases, begin the process of lipid digestion
  • leave significant digestion to occur later in small intestine
• Accessory structures of digestive system

  Major Salivary glands

  Three pairs of major salivary glands