Digestive system Flashcards
what is the Digestive tract also called?
alimentary tract or canal
what are some of the parts of the Digestive tract and accessory organs?
◦ Tube from oral cavity to
anus
◦ GI tract: refers to
stomach and intestines
Accessory organs
◦ Primarily glands, secrete fluids into tract
what are the functions of the digestive tract? part 1
- Ingestion: introduction of food into stomach
- Mastication: chewing
◦ Increases surface area - Propulsion
◦ Deglutition: swallowing
◦ Peristalsis: moves material through digestive tract - Mixing – contractions to increases contact with enzymes
what are the functions of the digestive tract? part 2
- Secretion: lubricate, liquify, digest
◦ Mucus: secreted along entire digestive tract, lubricates food and lining, protects from mechanical digestion, acid and digestive enzymes
◦ Water: makes food easier to digest and absorb
◦ Bile: emulsifies fats
◦ Enzymes: chemical digestion - Digestion: Mechanical and chemical
- Absorption: Movement from tract into circulation or lymph
- Elimination: Waste products removed from body;
Defecation
what is the Histology of the digestive tract-Mucosa?
Mucosa. Innermost layer, consisting of:
- Mucous epithelium
- Lamina propria: loose C.T.
- Muscularis mucosae: smooth muscle.
• Mucosa extends into lamina propria in places to
form intestinal glands or crypts.
what is the Histology of the digestive tract-Submucosa?
Thick C.T. layer with nerves,
blood vessels, small glands. Parasympathetic submucosal plexus.
what is the Histology of the digestive tract-Muscularis?
2 or 3 layers of smooth muscle, including circular and longitudinal layers.
Muscularis contains the myenteric plexus between circular and longitudinal layers. Plexus controls movements along GI tract.
what is the Histology of the digestive tract-Serosa or adventitia?
Connective tissue.
regulation of the Digestive system-Nervous system?
• Local: enteric nervous system
◦ Coordinates peristalsis and
regulates local reflexes
• General: coordination with the CNS.
◦ May initiate reflexes because of sight, smell, or taste of food.
◦ Primarily parasympathetic
regulation of the Digestive system-Chemical system?
• Production of hormones
– Gastrin, secretin
• Production of paracrine
chemicals like histamine
Saliva and its function
• Compound alveolar salivary glands produce saliva
◦ Prevents bacterial infection
◦ Lubrication
◦ Contains salivary amylase that breaks down
◦ Helps to form bolus for swallowing
◦ Parasympathetic input causes salivary production
stomach and its openings
◦ Gastroesophageal: from oesophagus
◦ Pyloric: to duodenum
what is the first stage of the Cephalic phase?
The taste, smell, or thought of food or tactile sensations of food in the mouth stimulates oblongata
what is the second stage of the Cephalic phase?
Vagus nerves carry parasympathetic action potentials to the stomach, where enteric plexus neurons are activated.
what is the third stage of the Cephalic phase?
Postganglionic neurons stimulate secretion by parietal and chief cells and stimulate gastrin and histamine secretion by endocrine cells
what is the fourth stage of the Cephalic phase?
Gastrin is carried through the circulation back to the stomach, where, along with histamine, it stimulates secretion
what is the first stage of the Gastric phase?
Distention of the stomach stimulates mechanoreceptors and activates a parasympathetic reflex. Action potentials generated by the mechanoreceptors are carried by the vagus nerves to the medulla oblongata
what is the second stage of the Gastric phase?
The medulla oblongata increases action potentials in the vagus nerves that stimulate secretions by parietal and chief cells and stimulate gastrin and histamine secretion by endocrine cells