Digestive system Flashcards
Four layers of the digestive tubes
Mucosa: Inner layer, epithelial cells Submucosal: layer of connective tissue Muscularis: Smooth muscle with two sublayers Longitudinal and circular Serosa: Outer layer, thin membrane
Sphincters
- sphincter muscles relax opening the passageway
- Sphincter muscles contract closing the passagway
Ingestion
intake of food via the mouth
Digestion
mechanically or chemically breaking down food into their subunits
Movement
food must be moved along the GI tract in order to fulfill all functions; mixing
Absorption
movement of nutrients across the GI tract wall to be delivered to cell via the blood (From lumen to cardiovascular system. Enter blood stream. )
Elimination
removal of indigestible molecules; defecation
Chewing and Swallowing
- Food processing begins the moment food enters your mouth (mechanical and chemical digestion)
- mechanical digestion increases surface area
- Enzymes begin chemical digestion of starches
Teeth
- Twenty primary teeth; thirty-two adult teeth
- Tooth structure: enamel, dentin, and pulp
- Shape of a tooth fits its function
- Incisors (chisel-shaped); bite off chunks of food
- Canines (cone-shaped); tear food
- Premolars and molars (broad crowns and rounded cusps); grind food
Three salivary glands
Parotid
Submandibular glands
Sublingual glands
Saliva
Mostly water
Bicarbonate buffer: used maintain the pH of our saliva. (when you eat something acidic, it will try to neutralize it)
Mucons: protection and lubrication
Salivary amylase: begins starch digestion
Formation of a bolus
Food lubricated in mouth
Role of hard palate and tongue
Pharynx connects with
Trachea
Esophagus
Steps of swallowing
- Muscular contractions push bolus to the pharynx:(Pharyngeal involuntary stage)
- Epiglottis closes larynx
- Uvula covers nasal cavity opening
- Breathing stops momentarily
- Bolus moves down esophagus into stomach (Esophageal involuntary stage)
Peristalsis
- moves bolus down to stomach
- Lower esophageal sphincter (LES) opens
The Stomach
- Muscular (three sublayers), stretchable sac
- Mixes and stores ingested food
- Secretions
- Forms chyme
- Food passes to the small intestine through the pyloric -
sphincter due to peristalsis - Empty stomach has folds called rugae
Gastric juice
- Water
- Parietal cells – HCl and intrinsic factor (Vitamin B12 absorption)
- Mucus: lubricant and protectant
- Chief Cells - Pepsinogen → pepsin; begins protein digestion
- Hydrogen steals bond, to satisfy need of the acid
- One of the strongest acids
- Digestion is not over in the stomach
- Thick layer of mucous that protected lining of stomach from the acid.Breaks down all molecules. If it thins out, you can get an ulcer (digests your own stomach) Can lead to hole in stomach.
- Chief cells: pepsinogen is inactive, the active form is -
- pepsin: breaks down peptide bonds (amino acids [proteins]) pH-2 (can only work in stomach)
- Helicobacter pylori:can cause cancer: Thin mucous, stomach gets eaten away.