Chapter24: Lecture Midterm II Flashcards
Digestive system
consists of a group of organs that break down the food we eat into smaller moelcules that can be used by body cells
The digestive canal (gastrointestinal tube)
a continuous tube that extends through the thoracic and abdominal cavities from the esophagus to the anus through the thoracic and abdominopelvic cavities
Organs of the digestive canal include
- esophagus
- stomach
- small intestine
- large intestine
- anal canal
The accessory digestive organs include
- mouth
- teeth
- tongue
- salivary glands
- pharynx
- liver
- gallbladder
- and pancreas
What helps to breakdown food in the stomach
muscular contractions in the wall of the digestive canal physically breakdown the food by churning it and propelling the food along the canal from the esophagus to the anus
6 Basic functions of the digestive system
- ingestion
- secretion
- mixing and propulsion
- digestion
- absorption
- defecation
What does the secretion phase of the digestive system do
releases water, acid, buffers and enzymes into the lumen of the digestive canal
What does the mixing and propulsion stage of the digestive system do
churns, and moves food through the digestive canal
Each day, cells within the wall of the digestive canal and accessory digestive organs secrete a total of
7 litres of water, acid, buffers and enzymes into the lumen of the digestive canal
From the esophagus to the anal canal there are 4 layers of tissues from deep to superficial:
- mucosa
- submucosa
- muscular layer
- serosa/adventitia
The mucosa
- inner lining of the digestive canal
- composed of epithelium, lamina propria and muscularis mucosae
The epithelium layer of the mucosa in the mouth, pharynx, esophagus and anal canal is
non keratinized stratified squamous epithelium that serves a protective function
The stomach and intestines epithelium layer is
simple columnar epithelium; functions in secretion and absorption
the type of exocrine cells that secrete mucus and fluid into the lumen of the digestive canal
enteroendocrine cells
The lamina propria
is areolar connective tissue containing many blood and lymphatic vessels, which are routes by which nutrients absorbed into the digestive canal reach other tissues of the body
The lamina propria supports the
epithelium and binds to the muscularis mucosa
The lamina propria contains what cells
MALT
- prominent lymph nodules contain immune system cells that protect against disease
Muscularis mucosae
thin layer of smooth muscle fibers
- throws the mucous membrane of the stomach and small intestine into many small folds, which increase the surface area for digestion and absorption
Movement of the muscularis mucosae ensures that
all absorptive cells are fully exposed to the contents of the digestive canal
The submucosa
consists of areolar connective tissue that binds the mucosa to the muscularis
- contains many blood and lymphatic vessels that recieve absorbed food molecules
- contains glands and lymphatic tissue
The submucosa also contains an extensive network of
neurons known as the submucosal neural plexus
Muscular layer of the mouth, pharynx, superior and middle parts of the esophagus contains
skeletal muscle that produces voluntary swallowing
- skeletal muscle also forms the external anal sphincter which permits voluntary control of defecation
Throughout the rest of the digestive canal the muscular layer consists of
smooth muscle that is found in two sheets;
- inner sheet: circular fibers
- outer sheet: longitudinal fibers
Involuntary contractions of smooth muscle in the digestive tract…
help break down food, mix it with digestive secretions and propel it along the digestive canal