30/31. Digestive System Flashcards
What is the digestive system?
Alimentary canal (gastrointestinal tract) and accessory digestive organs
Digestive functions
Ingestion
Propulsion
Mechanical breakdown
Chemical digestion
Absorption of nutrients and water
Defecation
Where does ingestion occur?
Through oral cavity
What does propulsion consist of
Swallowing and peristalsis
What is mechanical breakdown
Chewing
Mixing/segmentation
What is chemical digestion
Use of enzymes to breakdown food molecules
Epithelia of GI tract
Stratified squamous = protection
Simple columnar = absorption and secretiom
Where is stratified squamous epithelium in the GI tract
Oral cavity
Pharynx
Esophagus
Anus
Where is simple columnar epithelium in the GI tract
Stomach
Small and large intestines
Components of the mouth and oral cavity
Oral cavity
Vestibule
Uvula
Palatine tonsil
Frenula
Pharynx
Tonsils
Epiglottis
Location of oral cavity
Between teeth
Opens into oropharynx
Location of vestibule
Between teeth and lips
What is the uvula
Muscular structure that hangs from soft palate
Location and components of palatine tonsil
Sits between palatoglossal and palatopharyngeal arches
Palatoglossal arches is muscular arch from palate to tongue
Palatopharyngeal arch is muscular arch from palate to pharynx
What are frenula
Folds of mucosa
Consists of labial (lip) and lingual (tongue)
Pharynx consists of
Nasopharynx
Oropharynx
Laryngopharynx
What are tonsils
Lymphoid organs that fight against microorganisms entering the oral and nasal cavities
What is the epiglottis
Flap of cartilage, folds over airway to prevent material entering trachea
Permanent dentition (adult)
2 incisors, 1 canine, 2 premolars, 3 molars per quadrant
4 quadrants
Total 32 teeth
Deciduous dentition (baby teeth)
2 deciduous incisors, 1 deciduous canine, 2 deciduous molars per quadrant
4 quadrants
20 teeth total
Characteristics of the tongue
Muscular structure that manipulates foot in the oral cavity
Largest muscle extends from anterior mandible
Assists with production of certain sounds in speech
Tiny projections of mucous membrane on tongue are called papillae, which contain taste buds
Characteristics of tonsils
Lymphatic tissue in the back of nasal and oral cavities
Palatine tonsils are between palatoglossal and palatopharyngeal arches and are most often removed due to infection (tonsilitis)
Lingual tonsil found at back of tongue
Pharyngeal tonsils (adenoids) found in back of nasopharynx
Function and types of salivary glands
Produce saliva to begin chemical digestion, lubricates oral cavity, protects against tooth decay and microorganisms
Parotid gland, submandibular gland, and sublingual gland
Characteristics of parotid gland
Parotid duct pierces buccinator
Opens across from M2
Serous secretions
Characteristics of submandibular gland
Duct opens near frenulum of tongue
Serous and mucus secretuons
Characteristics of sublingual gland
Many ducts open underneath tongue
Mucus secretions
Layers of tube from esophagus to large intestine
Mucosa
Submucosa
Muscularis externa
Serosa/adventitia
Characteristics of mucosa layer
Epithelium and connective tissue
Muscularis mucosae
Characteristics of submucosa layer
CT with mucin glands, lymphoid tissue, blood vessels, and nerves
Characteristics of Muscularis externa
2 or 3 layers of smooth muscle
Circular and longitudinal muscle layers
Characteristics of serosa/adventitia layer
Outer layer of connective tissue
Serosa covered by peritoneum, adventitia is not
What is segmentation
Mixes material with digestive secretions
What is peristalsis
Wave of contraction propels material through GI tract
Characteristics of esophagus
Muscular tube connecting pharynx to stomach
Transitions from skeletal muscle to smooth muscle
Does not absorb nutrients
Passes through diaphragm to enter abdomen
Esophageal sphincter between esophagus and stomach prevents reflux
Features of the stomach
Fundus- dome of stomach
Body- large middle region
Pylorus- funnel shaped end of stomach
Pyloric sphincter- controls food leaving stomach
Rugae (gastric folds)- folds within stomach, allow for expansion
Layers and function of stomach
3 layers of Muscularis externa
Functions: churning, secretions, absorption of water and electrolytes
What is gastroesophageal reflux disease
Regurgitation of stomach contents into esophagus (acid reflux)
Causes heartburn and can lead to ulcers in esophagus
Can be caused by hiatal hernia (stomach pushes through diaphragm)
Stomach cells
Gastric pits in stomach open into gastric glands which contain :
Mucous neck cells
Parietal cells
Chief cells
Enteroendocrine cells
Undifferentiated stem cells
Function of mucous neck cells
Produce mucus (protect stomach)
Function of parietal cells
Produce HCl and gastric intrinsic factor (protein for absorbing vitamin B12)
Function of chief cells
Secrete pepsin (protein breakdown) and gastric lipase (for fat digestion)
Function of enteroendocrine cells in stomach
Secrete hormone gastrin (stimulate HCl secretion)
Function of undifferentiated stem cells
Replace epithelial lining of stomach every 3-7 days
Components of small intestine
Duodenum- 1st part, shortest, receives bile from liver and gallbladder and digestive enzymes from pancreas
Jejunum - 2nd, main region for chemical digestion and nutrient absorption
Ileum - 3rd, longest, contains ileocecal valve which controls movement of material into large intestine
Characteristics of small intestine
About 20 ft long
Mucosa has ridges called circular folds
Finger-like villi increase surface area for absorption and each villus contains capillaries and lymphatic vessels
Consists of entereocytes, goblet cells, enteroendcrine cells, and brunner glands
Function of enterocytes
Absorptive cells, cover villi in small intestine
Function of goblet cells
Produce mucus for lubrication
Location and Function of enteroendocrine cells in small intestine
In duodenum
Secrete hormones for release of bile and digestive enzymes
Location and Function of brunner cells
In submucosa of duodenum
Secrete alkaline mucus to protect against acidic material
Parts of large intestine
Cecum - 1st, has junction with ileum
Vermiform appendix- tube attached to cecum
Ascending colon- 2nd, ascends right side of abdomen
Transverse colon- 3rd, travels horizontal across abdomen
Descending colon- 4th, descends left side of abdomen
Sigmoid colon- 5th, S-shaped part that transitions into rectum
Characteristics of large intestine
5 ft long
Includes teniae coli, which are 3 external longitudinal bands of smooth muscle that shorten long intestine during peristalsis
Includes pouches called haustra
Includes goblet cells to produce mucus for lubrication
Large intestine absorbs mostly water and few nutrients
Characteristics of anus
Terminal part of large intestine
Sphincter muscles control storing or release of feces
Internal anal sphincter is made of smooth muscle and controlled by ANS
External anal sphincter is made of skeletal muscle and controlled by somatic motor system
Infants lack control over external anal sphincter
Defecation
Sympathetics store vexes by relaxing wall of rectum and contracting internal anal sphincter
Parasympathetics release feces by relaxing internal anal sphincter and contracting rectum
Can override this reflex by contracting external anal sphincter to store flexes until convenient
What is diverticulosis
Out-pouching of the wall of the colon
Weakening of colon wall associated with lack of fiber
What is diverticulitis
When diverticula become inflamed and infected
Can cause perforation of colon, leaking feces into peritoneal cavity and infecting peritoneum (peritonitis)
What is appendicitis
Inflammation of the vermiform appendix caused by blockage, infectious bacteria gets trapped
Pain starts around umbilicus, over to lower right quadrant
Physician will palpate at McBurney’s point, pain during palpitation indicates appendicitis
Appendectomy is surgical removal of appendix
Accessory digestive organs
Liver
Gall bladder
Pancreas
Characteristics of the liver
Largest gland in body
Upper right quadrant of abdomen, below diaphragm
2 lobes - right and left, divided by falciform ligament, which is membrane that anchors liver to anterior abdominal wall
Gallbladder tucked under right lobe
Inferior vena cava travels behind liver to heard
Considered exocrine gland because of ducts
Functions of liver
Produce bile (stored in gallbladder) to breakdown fats
Stores glucose from blood as glycogen to be used by body
Detoxifies blood
Makes blood proteins
Blood supply to liver
From celiac trunk (oxygen rich) and from hepatic portal vein (oxygen poor that is nutrient rich and needs filtration)
Structure of liver
Consists of hexagonal lobules made of hepatocytes (liver cells)
Every corner of lobule has arteriole from celiac trunk, venule from hepatic portal, bile duct
Filtration and exit of blood from liver
Blood from venules and arterioles mix in liver sinusoids
Venous blood is cleansed and filtered by hepatocytes and macrophages
Arterial blood supplies oxygen to hepatocytes
Blood in sinusoids collects in central vein which carries blood to hepatic veins and then IVC
Characteristics of pancreas
Mixed gland- both endocrine and exocrine function
Exocrine: has acinar cells that produce and secrete mucin and digestive enzymes to aid in digestion, which are transported by pancreatic duct which joins common bile duct
Endocrine: has islet cells which produce insulin
Characteristics of gallbladder
Stores bile produced by liver
Released when fatty food enters the small intestine
Characteristics of biliary tree (apparatus)
Passageway of ducts carrying bile
Liver secretes bile into hepatic ducts
Gallbladder secretes bile into cystic duct
Cystic duct and hepatic duct merge to form common bile duct
Common bile duct meets pancreatic duct and they empty into duodenum at duodenal papilla
What is cholecystitis
Inflammation of gallbladder
Often caused by gallstones due to too much cholesterol in diet or sudden changes in fat content of diet
May require surgical removal (cholecystectomy) if stones can’t be broken up
Characteristics of peritoneum
Serous membrane lining the abdominal cavity
Abdominal organs grow in abdominal cavity and are surrounded by peritoneum
Mesentery- double layer of peritoneum that collapses behind organs (nerves and blood vessels are trapped between layers of peritoneum; organs without mesentery are retroperitoneal)
