HISTOLOGY- DIGESTIVE

• the digestive system consists of:

  
  

  • oral cavity
  • esophagus
  • stomach
  • small intestine
  • large intestine
  • anus
• what are the associated glands (accessory organs) of digestive system:

  
  

  -salivary glands

  -pancreas

  -liver
• Digestive system is also known as ____ and ____

  
  

  
  

  • GASTROINTESTINAL TRACT
  • ALIMENTARY CANAL
• Most water and electrolytes are absorbed in the:

  
  

  large intestine
• Structures within the digestive tract allow the following:

  
  

  
  

  • Ingestion
  • mastication
  • motility
  • secretion
  • chemical digestion
  • hormone release
  • absorption
  • elimination
• INGESTION - is the introduction of food and liquid into the oral cavity
• Mastication is also known as?

  
  

  chewing
• what process divides solid food into digestible pieces?

  MASTICATION
• it is the muscular movements of materials through the tract.

  
  

  motility
• the process of producing lubricating and protective mucus, digestive enzymes, acidic, and alkaline fluids, and bile.

  SECRETION
• It is for local control of motility and secretion:

  
  

  
  

  Hormone release
• It is the enzymatic degradation of large macromolecules in food to smaller molecules in food to smaller molecules and their subunits.

  Chemical digestion
• Absorption of small molecules and water goes into: (2 answers)

  • blood
  • lymph
• It is a hollow tube with a lumen of variable diameter and a wall made up of four main layers.

  Gastrointestinal tract
• What are the four main layers of GI TRACT:

  • MUCOSA
  • SUBMUCOSA
  • MUSCULARIS
  • SEROSA
• the mucosa layer consists of epithelial lining
• epithelial lining of mucosa - is an underlying lamina propria of loose connective tissue rich in blood vessels, lymphatics, and lymphocytes, smooth muscle cells, and small glands
• Muscularis mucosae - a thin layer of smooth muscle separating mucosa from submucosa and allowing local movements of the mucosa
• mucosa is also known as mucous membrane
• Submucosa - contains denser connective tissue with larger blood and lymph vessels, glands, and significant lymphoid tissue
• the submucosa contains the Meissner plexus of autonomic nerves
• Muscularis is also known as muscularis externa
• Muscularis - layer that composed of smooth muscle cells organized as two or more sublayers
• the fiber orientation of muscularis internal sublayer is circular, while the fiber orientation of muscularis external sublayer longitudinal
• the connective tissue between the muscularis muscle sublayers contains blood vessels, lymph vessels, and Auerbach nerve plexus
• Auerbach nerve plexus - many autonomic neurons aggregated into small ganglia and interconnected by pre-and postganglionic nerve fibers
• Auerbach nerve plexus and Meissner plexus comprise the enteric nervous system of GI tract
• Contractions of the muscularis are generated and coordinated by myenteric plexus
• serosa - a thin sheet of loose connective tissue, rich in blood vessels, lymphatics, and adipose tissue, and covered with a simple squamous covering epithelium or mesothelium
• Serosa - the outermost layer of the digestive tract located within the abdominal cavity
• the serosa of the small and large intestine is continuous with portions of the mesentery
• Mesentery - a large fold of adipose connective tissue, covered on both sides by mesothelium, that suspends the intestines and is continuous with the peritoneum
• peritoneum - the serous membrane lining the abdominal cavity
• esophagus lacks serosa but has thick adventitia
• mucosa-associated immune defense system: provides an essential backup to the thin physical barrier of the epithelial lining
• oral cavity is lined with stratified squamous epithelium which can be keratinized, partially keratinized, and nonkeratinized depending on the location
• Oral epithelium undergoes continuous desquamation
• the keratinized cell layer resist damage from abrasion and are best developed in the masticatory mucosa on the gingiva and hard palate
• nonkeratinized squamous epithelium predominates in the lining mucosa over the soft palate, cheeks, the floor of the mouth, and pharynx
• throughout oral cavity, the epithelium contains transient antigen-presenting cells and rich sensory innervation