Digestive System Flashcards
consists of a group of organs that break down the food we eat into smaller molecules that can be used by body cells
Digestive System
2 GROUPS OF DIGESTIVE SYSTEM
- Gastrointestinal (GI) Tract
- Accessory Digestive System
continuous tube that extends from the mouth to the anus through the thoracic and abdominopelvic cavities.
Gastrointestinal (GI) Tract/ Alimentary Canal
GI TRACT INCLUDES?
mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
How long is GI tract
5-7 meters
7-9 in cadavers
food is masticated and converted into a bolus by insalivation
Mouth
are the organs of swallowing
Pharynx and Esophagus
digestive process begins
Stomach
digestive process is completed
Small intestine
an organ of egestion and water absorption that terminates at the anus.
Large Intestine
Accessory Digestive System include the:
teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
aid in the physical breakdown of food
teeth
assists in chewing and swallowing.
tongue
FUNCTIONS OF DIGESTIVE SYSTEM:
Ingestion, secretion, mixing and propulsion, digestion, absorption, and defecation
taking food into mouth.
ingestion
release of water, acid, buffers, and enzymes into lumen of GI tract.
secretion
churning and movement of food through GI tract.
mixing and propulsion
mechanical and chemical breakdown of food
digestion
2 types of digestion
Mechanical and Chemical Digestion
churns food
mechanical digestion
hydrolysis
chemical digestion
passage of digested products from GI tract into blood and lymph.
absorption
elimination of feces from GI tract.
defecation
LAYERS OF THE GI TRACT FROM INNER TO OUTER
Mucosa
Submucosa
Muscularis Mucosae
Serosa
Mucosa is composed of:
(1)layer of epithelium in direct contact with the contents of the GI tract
(2)layer of connective tissue called the lamina propria
(3)a thin layer of smooth muscle (muscularis mucosae).
protection, secretion, absorption
epithelum
epithelium in the mouth, pharynx, esophagus, and anal canal is mainly
nonkeratinized stratified squamous epithelium
nonkeratinized stratified squamous epithelium that serves a
protective function.
Simple columnar epithelium function as
secretion and absorption, lines the stomach and intestines.
firmly seal neighboring simple columnar epithelial cells to one another restrict leakage between the cells.
Tight junction
secrete mucus and fluid into the lumen of the tract
exocrine cells
secrete hormones
enteroendocrine cells
areolar connective tissue containing many blood and lymphatic vessels
lamina propria
routes by which nutrients absorbed into the GI tract reach the other tissues of the body.
lamina propria
supports the epithelium and binds it to the muscularis mucosae
lamina propria
prominent lymphatic nodules contain immune system cells that protect against disease.
MUCOSA-ASSOCIATED LYMPHATIC TISSUE (MALT)
throws the mucous membrane of the stomach and small intestine into many small folds, which increase the surface
area for digestion and absorption.
Muscularis mucosae
consists of areolar connective tissue that binds the mucosa to the muscularis.
submucosa
located in the submucosa is an extensive network of neurons known as
submucosal plexus
contains skeletal muscle that produces voluntary swallowing.
Muscularis
permits voluntary control of defecation.
external anal sphincter
Throughout the rest of the tract, the muscularis consists of smooth muscle that is generally found in two sheets:
inner sheet of circular fibers and an outer sheet of longitudinal fibers.
help break down food, mix it with digestive secretions, and propel it along the tract.
Involuntary contractions of the smooth muscle
Between the layers of the muscularis is a second plexus of neurons, the
myenteric plexus
Those portions of the GI tract that are suspended in the abdominal cavity have a superficial layer called
serosa
serosa is a serous membrane composed of
areolar connective tissue and simple squamous epithelium (mesothelium).
esophagus lacks a
serosa
Intrinsic set of nerves “brain of the gut”
enteric nervous system
The neurons of the ENS are arranged into two plexuses:
1.Myenteric plexus (plexus of Auerbach)
2.Submucosal plexus (plexus of Meissner
located between the longitudinal and circular smooth muscle layers of the muscularis and GI tract motility
Myenteric plexus (plexus of Auerbach)
- found within the submucosa.
- controlling secretions
Submucosal plexus (plexus of Meissner
The wall of the GI tract contains two major types of sensory receptors:
chemoreceptors and mechanoreceptors
respond to certain chemicals in the food present in the lumen
chemoreceptors
activated when food distends (stretches) the wall of a GI organ.
mechanoreceptors
Extrinsic set of nerves
Autonomic Nervous System
increases secretion and activity by stimulating ENS
Parasympathetic stimulation
decreases secretions and activity by inhibiting ENS
Sympathetic stimulation
supply parasympathetic fibers to most parts of the GI tract
vagus (X) nerves
supply the GI tract form neural connections with the ENS.
parasympathetic nerves
largest serous membrane of the body
Peritoneum
Peritoneum is divided into:
Parietal peritoneum
Visceral peritoneum
Peritoneum consists of a layer of
simple squamous epithelium (mesothelium)
lines the wall of the abdominal cavity
Parietal peritoneum
covers some of the organs in the cavity and is their serosa
Visceral peritoneum
5 MAJOR PERITONEAL FOLDS:
Greater omentum, falciform ligament, lesser omentum, mesentery, and mesocolon
-longest peritoneal fold
-folds back on itself, giving it a total of four layers.
-contains a considerable amount of adipose tissue.
Greater omentum
contribute macrophages and antibody-producing plasma cells that help combat and contain infections of the GI tract.
lymph nodes
attaches the liver to the anterior abdominal wall and diaphragm.
Falciform ligament
only digestive organ that is attached to the anterior abdominal wall.
liver
