Digestive System Flashcards
What organs make up the GI tract?
Mouth (oral cavity), pharynx, esophagus, stomach, small intestine, large intestine
What are the accessory organs?
Liver, gallbladder, pancreas
What are the functions of the digestive system?
Digestion - breaking down ingested food (mechanical digestion vs. chemical digestion)
Absorption - entry of nutrients into the cell lining the GI tract en route to the blood or lymph
Defecation - elimination of wastes and indigestible substances
What are the layers of the GI tract?
Mucosa, submucosa, muscularis, serosa
Describe muscosa.
Inner lining composed of layers of epithelial tissue, connective tissue and smooth muscle
Epithelial tissue layer - contains glandular cells that serve both exocrine functions (secrete mucus and fluid) and endocrine functions (secrete hormones)
Connective tissue layer - contains blood vessels and lymphatic vessels that collect absorbed nutrients
Smooth muscle layer - creates folds in the lining of the stomach and small intestine that increase surface area for digestion and absorption
Describe submucosa.
Mass of connective tissue that binds mucosa and the muscularis
Describe muscularis.
Contains layers of skeletal muscle (mouth, pharynx, upper, esophagus) or smooth muscle (the rest of the GI tract)
Contraction of these muscles assists in the mechanical digestion and movement of food through the GI tract (“motility”)
Describe serosa.
Mix of connective/epithelial tissue that forms part of the peritoneum - helps suspend portions of GI tract located within abdominal cavity
Mesentery - portion of peritoneum that suspends the small intestine (superior/inferior mesenteric artery/vein)
What nerves are associated with taste and salivary glands?
CN VII (facial nerve)
CN IX (glossopharyngeal nerve)
What is the role of the teeth?
Assist in the mechanical digestion of food
What is the role of the tongue?
Assists in the mechanical digestion of food
Contains taste buds, sensory receptors that provide taste sensations (CN VII, CN IX)
Contains glands which secrete a digestive enzyme that assist in chemical digestion of lipids (in the stomach)
What is the role of the palate?
Separates oral cavities, nasal cavities and nasopharynx
Hard palate - anterior portion form by maxilla and palatine bones (covered by mucous membrane)
Soft palate - posterior portion formed by skeletal muscle (covered by mucous membrane)
Vulva - muscular process that hangs off the posterior border of the soft palate
During swallowing, soft palate and uvula are pulled superiorly to prevent food from entering the nasal cavity
What is the role of the salivary glands?
Secrete saliva, which is a mix of water, ions and digestive enzyme
Receive sympathetic innervation and parasympathetic innervation (CN VII and CN IX)
What is the role of the phayrnx?
Oropharynx and laryngopharynx function as a passageway for food from the mouth to the esophagus
Muscular contractions in these areas help propel food along and prevent it from entering the larynx (epiglottis)
What is the role of the esophagus?
Muscular tube that functions as a passageway for food from the pharynx to the stomach
Descends through thoracic cavity posterior to the trachea and enters the abdominal cavity through the esophageal hiatus in the diaphragm
There are sphincters of smooth muscle at either end, which regulate the passage of food into (upper esophageal sphincter) and out of (lower esophageal sphincter) the esophagus
What is the role of the stomach?
Assist in mechanical/chemical digestion of food
Store partially digested food before it enters the small intestine
There is a sphincter of smooth muscle (pyloric sphincter) which regulates the passageway of food into the small intestine
What is the role of the small intenstine?
Primary site of chemical/mechanical digestion + absorption of food along the GI tract
Exocrine gland cells - secrete “intestinal juice” which contains digestive enzymes that assist in the chemical digestion of food
What is the role of the large intestine?
Tube that functions as a passageway for by-products of digestion from the small intestine
Contains an abundance of bacteria that assist in the final stages of chemical digestion, a process that produces gas (flatulence) as well as some vitamins
Absorption of water, ions and some vitamins
Elimination of digestive wastes and indigestible products
What are the three parts of the small intestine?
Duodenum (“proximal portion”)
Jejunum (“middle portion”)
Ileum (“distal portion”)
What are the three parts of the large intestine?
Transverse colon (“middle” portion)
Ascending colon (“proximal” portion)
Cecum
Vermiform appendix (possible immune function)
Descending colon (“distal” portion)
Sigmoid colon
Rectum and anal canal
What is the role of the pancreas?
Secretes “pancreatic juice” into GI tract (exocrine)
What is the role of the liver?
Secretes biles, which assists in chemical digestion of lipids
Detoxifies blood
Involved with metabolism of carbohydrates, lipids and proteins
Stores glucose (glycogen) as well as several vitamins and minerals
Produces the active form of vitamin D (in conjunction with kidneys)
What is the role of the gallbladder?
Stores and concentrates bile produced by the liver and releases it into the small intestine when needed
Describe the regulation of the digestive system by the enteric nervous system and autonomic nervous system.
The GI tract contains intrinsic plexuses of nerves referred to as the enteric nervous system (ENS)
Receives sensory input from the GI tract (chemoreceptors, stretch receptors)
Sends motor signals to the glands and smooth muscle of the GI tract
The ENS is regulated extrinsically by neurons from the ANS
Sympathetic - decreases GI activity
Parasympathetic - increases GI activity
