Lecture 12: Digestive system Flashcards
The upper and lower digestive tracts make up what
the alimentary canal
What are the 4 parts of the upper digestive tract
- mouth
- pharynx
- esophagus
- stomach
What are the 3 parts of the lower digestive tract
- small intestine (duodenum, jejunum, lleum)
- large intestine (cecum, colon, rectum)
- anus
What are the 7 accessory organs of the digestive system
- salivary glands (parotid, submandibular, sublingual)
- tongue
- teeth
- liver
- gallbladder
- pancreas
- appendix
What are the 6 main functions of the digestive ssytem
- ingestion
- mechanical breakdown
- propulsion
- digestion
- absorption
- defecation
what parts of the digestive system are involved in mechanical breakdown of food
- mouth = chewing
- stomach = churning
- small intestine = segmentation
Where does propulsion occur and how
- oropharynx = swallowing
- Peristalsis in esophagus, stomach, small intestine, large intestine
What are the 4 structural layers of the alimentary canal
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa or adventitia
What makes up the mucosa layer of alimentary canal
membrane lining cavities that open to the exterior
- mucous epithelium (mouth, esophagus, anal canal)
- Lamina propria
- muscularis mucosae
What makes up the submucosa layer of alimentary canal
- gland in submucosa
- duct from gland
What makes up the muscularis layer of alimentary canal
- circular muscle layer
- longitudinal muscle layer
What makes up the serosa layer of alimentary canal
- connective tissue layer
- peritoneum / Mesothelium
What are the roles of the mucosa layer of the alimentary canal
- secretion (mucus, enzymes, hormone)
- absorption (nutrients)
- protection (infectious diseases)
What are the roles of the submucosa layer of the alimentary canal
- contains loose ct, blood & lymphatic vessels, neural fibers
- submucosal plexus (part of ENS)
- stomach (has lots of elastic fibers so it regains form after distention)
Where is the voluntary / skeletal muscles of the muscularis externa found
-mouth pharynx, superior part of esophagus, external sphincter (valve) of anus
Where is the internal / smooth muscle of the muscularis externa found
rest of tube
the serosa layer interfaces with what
the peritoneum (visceral/ parietal)
The mouth is a structure of what cavity
oral or buccal
describe the lips of mouth
covered externally by skin and internally by mucous membrane
Describe cheeks of mouth
- lateral boudaries, continuous w/ the lips and lined by mucous membrane
- formed in large part by the buccinator muscle covered by adipose tissue
- contain mucous-secreting glands
Describe the hard palate of the mouth
-consists of portions of 4 bones : 2 maxillae and 2 palatines
Describe the soft palate of the moutth
- forms the partition btw the mouth and nasopharynx and is made of muscle arranged in an arch
- suspended from the midpoint of the posterior border of the arch is the uvula
What is the tongue
solid mass of skeletal muscle covered by a mucous membrane; extremely maneuverable
What are the 3 parts of the tongue
- root
- tip
- body
What 2 areas of tongue have papillae
dorsal and lateral surfaces
what anchors the tongue to the floor of the mouth
lingual frenulum
What is importance of intrinsic and extrinsic muscles of the tongue
intrinsic: speech & mastication
Extrinsic: swallowing & speech
How much saliva do the salivary glands excrete per day
~1L
What are the 3 main pairs of compound tubuloalveolar glands
- Parotid glands (largest pair, make watery saliva w/ enzymes)
- Submandibular glands (contain enzyme & mucous producing elements)
- Sublingual glands (smallest of pairs, make mucous type o saliva)
What are the teeth
organs of mastication
What are the 4 parts of the teeth
- crown
- neck
- root
- outer shell
what is the crown of the tooth
exposed portion of a tooth
what is the neck portion of a tooth
narrow portion that joins the crown to the root, surrounded by gingivae (gums)
what is root part of tooth
fits into the socket of jaw and is suspended by a fibrous periodontal membrane composed of many periodontal ligaments
What is the outer shell made up of
- Dentin: most of tooth shell, covered by enamel at the crown & cementum at the neck & root
- Pulp cavity: located in dentin, contains c.t., blood, lymphatic vessels & sensory nerves
What is pharynx and esophagus role in digestive system
-Bolus passes through on way to stomach
What are the 3 segments of the esophagus
- Cervical
- Thoracic
- abdominal sections
What is structure of esophagus
- lined with stratified squamous epithelium
- 2 sphincters: Upper in cervical part (relaxation can = belching)…Lower at junction of stomach (relaxation can = acid reflux/ heart burn)
What are the 4 divisions of the stomach
- Cardia (collarlike region @ junction w/ esophagus)
- Fundus (to left and above the opening of the esophagus into the stomach)
- Body (central part)
- Pylorus (lower part of stomach)
The stomachs extra layer of muscle is to
- can contract at many angles
- enhances the stomachs ability to mix it’s contents
what controls opening into stomach
lower esophageal sphincter
What control opening out of stomach into small intestine
pyloric sphincter
The epithelial lining of the stomach has
rugae with depressions called gastric pits
What secretes most of the gastric juices in stomach
gastric glands found below the level of the pits
What secretes enzymes of gastric juices in stomach
Chief cells found in the gastric glands
What cells secrete hydrochloric acid in the stomach
Parietal cells found in the gastric glands
What cells secrete gastrin and ghrelin
Endocrine cells
how long is the small intestine
~2.5 cm in diameter and 6 m in length
What are 3 divisions of the small intestine
- Duodenum (uppermost division, ~25cm long like letter C)
- Jejunum (~2.5m long)
- Ileum (~3.5 m long)
Each villus of the wall of the small intestine contains
an arteriole, venule, and lacteal (lymph capillary)
The wall of small intestine villi are covered with what
brush border made up of 1700 ultrafine microvili per cell
-they along with villi help increase surface area of small intestine
What are the crypts that are located between villi
-contain stem cells from which other cell types are produced and then migrate upward to replace to replace old cells
What cells secrete enzyme that inhibit bacterial growth in crypts of small intestine
paneth cells
what is the size of the large intestine
diameter 6cm and legnth 1.5 to 1.8 m
what are the 3 divisions of the large intestine
- cecum (first 5 to 8 cm)
- colon
- rectum (last 7 or 8 inches, terminal inch is anal canal & opening = anus)
What is the ascending colon
vertical position on the right side of the abdo
-ileocecal valve prevents material from passing from the large intestine into ileum
What is the transverse colon
area that passes horizontlly across the abdo above small intestine
-extends from the hepatic flexure to the splenic flexure
What is descending colon
vertical position on left side of the abdo
Where is sigmoid colon
joins the descending colon to the rectum
What is the vermiform appendix
- 8 to 10 cm long
- thought of as vestigial
- research indicates may store healthy bacteria for the digestive system
What is structure of the liver
2 lobes separated by falciform ligament
-Hepatic lobules: anatomical units of the liver, a small branch of hepatic vein extends through center of each lobule
What are the bile ducts of the liver
- small bile ducts from R and L hepatic ducts
- R and L hepatic ducts immediately join to form one hepatic duct
- hepatic duct merges w/ cystic duct to form the common bile duct, which opens into the duodenum
What is the flow of bile
- Created in liver
- goes into bile ducts
- then goes through R and L hepatic ducts
- then through common hepatic duct
- merges with cystic duct from gallbladder
- to common bile duct
What is structure of gallbladder
-pear shaped sac 7 to 10 cm long and 3 cm wide at broadest point
What is function of gallbladder
- storage of bile
- concentration of bile fivefold to tenfold
what are gallstones
- often made of cholesterol
- can form when bile becomes concentrated
What is structure of pancreas
- grayish-pink gland 12 to 15 cm long
- behind stomach
- composed of endocrine and exocrine glandular tissue
What is the compound acinar arrangement that makes up the majority of the pancreas
- the exocrine portion
- tiny ducts unite to form the main pancreatic duct, which empties into the duodenum
- acinar cells secrete digestive juice and enzymes
What are the pancreatic islets (islets of Langerhans)
- endocrine portion of the pancreas
- imbedded between exocrine units
