Flashcards in Digestive System Deck (27)
What are the structures in the digestive system
oral cavity, oesophagus, small and large intestine, pharynx, stomach
What are the accessory structures in the digestive system?
Salivary glands, liver, gallbladder and pancreas
What are the functions of the digestive system?
Chemical digestion (stomach)
Secretion (salivary glands)
Food break down (oral cavity)
Storage and elimination
Absorption of nutrients micronutrients, ions and water, reabsorption of most secretions
What type of secretion does the digestion system do?
What does the digestive system secrete and which structures do this?
Mucus, water, HCO3-, bile, H+, ions and water by the salivary glands, liver, pancreas, stomach and small and large intestine
Note: Nearly all water is reabsorbed in small intestine
What are the layers of the digestive tract?
Describe the mucosa
It is the most superficial layer of the digestive tract, it contains loose CT and smooth muscle, contains lymphatic/ immune system cells. The mucosa secretes and absorbs.
Describe the submucosa
Sits below the mucosa of the digestive tract. It is made of CT and used to move and mix contents
Describe the Muscularis externa
Sits below the submucosa of the digestive tract. It is a double layer of loose CT with neurovascular structures
Describe the serous membrane
Epithelium and CT, contains visceral peritoneum on surface of gastrointestinal tract.
Describe the oral cavity
The oral cavity contains the mouth, teeth, salivary glands and is responsible for food mastication. Its functions are mechanical digestion, initiate swallowing and dissolve tastants
Describe the salivary glands
Salivary glands consist of mucus and serous glands. Saliva, water and ions are produced. An enzyme (amylase) dissolves starch. Salivary glands begin chemical digestion
Describe the Pharynx
The pharynx consists of the nasopharynx, oropharynx and laryngopharynx. The pharynx aids with swallowing and is a passage for air.
Describe the Oesophagus
Located in neck, thorax and abdominal cavity. It conveys ingested material to stomach by a muscular tube.
Swallowing moves food through the oral cavity to the pharynx then oesophagus and stomach.
Initiated voluntarily, then automatic (brainstem swallowing centre)
Describe the stomach
The stomach stores the meal and chemically and mechanically digests the food. It releases contents to small intestine.
The stomach mixes with food to form chyme (acidic). Secretions from the gastric glands include;
Mucus (to protect stomach from chyme)
Pepsinogen (protein digestion)
Gastric lipase (lipid digestion)
Describe the small intestine
The small intestine accepts food from stomach. it has three components;
Most of the digestion and absorption occurs here (nearly all water is re-absorbed)
The small intestine moves by smooth muscle contraction
Describe the pancreas
The pancreas produces pancreas juice which contains HCO3- and digestive enzymes
Pancreas also has endocrine roles
The pancreas performs much of chemical digestion in lumen of small intestine.
Describe the liver
The liver produces bile and bile salts The bile salts aid digestion and adsorption of fat by emulsifying fats, and solubilising the digestion products (increases surface area)
Describe the gallbladder
The gallbladder stores the bile and bile salts from liver
How does the small intestine increase its surface area?
It has folds of the mucosa snd submucosa. Villi (mucosa layer)
Microvilli on apical surface of epithelial cells
What does the small intestine secrete?
enzymes such as peptidases, various disaccharides and nucleosidases as well as water, ions and mucus.
Describe the chemical digestion that occurs in the small intestine
Phase 1 occurs in the lumen; Enzymes from pancreas (amylase, lipase etc) break covalent bonds in macromolecules to form smaller macromolecules
Phase 2 occurs at brush boarder; intestinal epithelial cell enzymes (peptidases, various disaccharide) complete digestion process
How does absorption occur in the small intestine?
• Simple diffusion
• Facilitated diffusion
• Secondary active transport
• Active transport
How is the digestive system related to the Hepatic portal venous system
Venous blood from the gut containing most absorbed nutrients goes to the hepatic portal vein. This blood them goes to the liver hen hepatic vein, to inferior vena cava, to right atrium.
It goes to the liver first to give it most access to the nutrients
Describe the large intestine
The large intestine includes; appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal
Its function is to storage, absorb water and ions and also to compact the luminal contents