Chapter 23- Digestive System Flashcards
Functions of the Digestive System
Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
Peritoneum
Abdominal serous membrane
Visceral- Lines organs
Parietal- Lines cavity walls
Mesentery
Double layer of peritoneum
Functions-
Hold organs in place
Fat storage
Route for blood vessels and nerves
Retroperitoneal organs
Those behind the peritoneum
Are not connected by a mesentery
Kidneys, pancreas, duodenum
Alimentary Canal
Digestive tube that runs though the body
Mouth, pharynx, esophagus, stomach, intestines
Accessory Digestive Organs
Assist in digestion
Teeth and tongue
Glands- Gallbladder, salivary glands, liver, and pancreas
Layers of the Alimentary Canal
Internal-
Mucosa
Submucosa
Muscularis externa
Serosa
External
Mucosa
The innermost layer of the alimentary canal
Components-
Epithelium (absorption or secretion) and glands
Lamina propria
Muscularis mucosae (local movements)
Lamina propria
Connective tissue portion of mucosa
Contains capillary beds and MALT
Submucosa
2nd layer of the alimentary canal
Contains blood and lymphatic vessels and nerves
Has elastic fibers for stretching and collapsing
Muscularis Externa
Contains the muscular portion of the alimentary canal
Circular muscularis
Longitudinal muscularis
Circular muscularis
Sphincter-like muscle within the alimentary canal
Performs peristalsis and segmentation
Peristalsis
Muscular action that is the major means of propulsion
Adjacent rings of muscle relax and contract to push bolus
Segmentation
Rhythmic local muscle contractions of non-adjacent segments that mix food and digestive juices
Longitudinal muscularis
Muscle that runs the length of the alimentary canal
Contraction shortens the overall tube length
Serosa
Most external layer of the alimentary canal
Forms the visceral peritoneum
Nerve plexuses serving the alimentary canal
Myenteric nerve plexus- Muscularis externa
Submucosal nerve plexus- Serves muscularis mucosae and glands
Oral cavity
Start of alimentary canal
Mucosa is stratified squamous
Muscle portion is made of orbicularis oris and buccinator
Labial frenulum
Connects lips to gums
Palate
Forms superior portion of the mouth
Tongue
Interlacing fascicles of muscles
Responsible for gripping and repositioning food, taste, and speech production
Teeth
Assist in tearing food and beginning of mechanical digestion
Deciduous teeth (20) appear at 6 months- 2 years
Permanent teeth (32) erupt by adolescence
Salivary glands
Tubuloalveoral glands that produce saliva
3 pairs-
Parotid (by ear)
Sublingual
Submandibular
Functions of saliva
Moisten mouth
Dissolve food for taste
Neutralize acid
Kill microorganisms
Begin starch digestion
Oropharynx and laryngopharynx
Passageway for air and food
Mucosa made of stratified squamous
Muscle layers are skeletal muscles-
Superior, middle, and inferior pharyngeal constrictors
Esophagus
Muscular tube connecting pharynx to stomach; passes through diaphragm
Mucosa- Stratified squamous with mucous glands for lubrication
Muscularis Externa- Transitions from skeletal to smooth muscle 1/3 of way through
Serosa- Called adventitia while in thoracic cavity
Stomach
Storage point of food
Anatomical features-
Fundus- Superior point
Lesser curvature- Inside, connects to lesser omentum
Greater curvature- Outside, connects to greater omentum
Pyloric end- Distal end of stomach
Pyloric sphincter- Closed end of stomach
Functions of the Stomach
Mechanical digestion- Churns food into chyme
Start of protein digestion
Absorption of water, fluids, and alcohol
Layers of the stomach
Muscularis externa- Additional oblique layer that assists in churning
Mucosa- Simple cuboidal; gastric pits
Gastric pits
Pockets within stomach lining
Gastric glands- Contain enteroendocrine cells that secrete gut hormones
Chief cells secrete pepsinogen
Lined with parietal cells- secrete HCl
Pepsin cycle
Chief cell- Secretes pepsinogen in gastric pit
Pepsinogen travels out of gastric pit past parietal cell
Parietal cell secretes HCL
HCl converts pepsinogen to pepsin
Pepsin enters lumen of stomach and begins protein breakdown
Small intestine
Longest portion of the alimentary canal
Duodenum- Receives digestive enzymes and bile
Jejunum
Ileum
Layers of the Small intestine
Mucosa-
Villi- Projections of mucosa with simple columnar, capillary beds, and lymph vessels
Microvilli- Cilia that increase surface area and secrete enzymes
Submucosa- Transverse ridges form circular folds that slow food for increased digestion
Cells in the small intestine
Absorptive cells
Goblet cells- Secrete mucus
Enteroendocrine cells
Intestinal crypts- Secrete intestinal juices
Large Intestine
Cecum- First portion; blind pouch for fecal storage
Appendix- Offshoot that contains lymphoid tissue
Colon
Rectum- Descends along inferior septum
Anal canal
Segments of the Colon
Ascending, Transverse, Descending, and Sigmoid
Muscle tone creates pockets called haustrum
Functions of the Large Intestine
Small amounts of digestion
Absorb water and electrolytes
Mass peristaltic movement of feces
Layers of the Large Intestine
Mucosa- No villi
Many goblet cells for lubrication
Simple columnar epithelium
Stratified squamous in anal canal
Liver
Largest gland in the body that performs many metabolic functions and produces bile
Liver Anatomy
4 lobes- Left, right, caudate (posterior) and quadrate
Hepatic artery feed liver oxygenated blood
Hepatic portal veins supply blood for filtration from small intestine
Hepatic veins empty filtered blood to vena cava
Hepatic ducts drain bile from liver to gallbladder
Bile Functions
Emulsifies fats for absorption by lymph ducts
Gallbladder
Stores and concentrates bile
Connected to liver by cystic duct
Connected to duodenum by common bile duct
Pancreas
Endocrine functions to regulate blood sugar with insulin and glucagon
Exocrine functions:
Acinar cells produce and store pancreatic enzymes
Enzymes travel through pancreatic duct to duodenum and promote digestion
