Module 10 Flashcards
Two Groups of the Digestive System
- Digestive Tract and 2. The Accessory Digestive Organs
The Digestive Tract (Alimentary Canal)
Mouth, oral cavity, pharynx, esophagus, stomach, small intestine, large intestine and anus
The Accessory Digestive Organs
Tongue, teeth, salivary glands, liver, biliary ducts and gallbladder and pancreas
Functions of the Digestive Tract
Continuous tube that starts in the oral cavity and ends inferiorly with the anal canal
Digestion
Masticiation crushes food into smaller pieces to facilitate chemical processing by enzymes into smaller molecules
Absorption
Digestion is completed in the small intestine where most nutrients are absorbed. In the large intestine, water, vitamines, etc are absorbed
Secretion
Cells of the stomach’s mucosal wall releases gastric acid to perform chemical digestion
Motility
When food is swallowed, muscles in the esophageal wall contract and relax to push food through the esophagus down to the stomach
Elimination of Waste
Leftover materials, which are not absorbed or utilized by the body are eliminated by the defecation
Mucosa - Digestive Tract
The innermost layer of the digestive tract wall and is composed of 3 main elements 1. surface epithelium 2. lamina propria 3. muscaris mucosa
What Does Surface Epithelium do
Reflects the expected function of the organ
Lamina Propria
Layer of loose connective tissue under the surface epithelium
Muscaris Mucosa
Smooth muscle fibres under the lamina propria
Submucosa
Layer below the mucosa, composed of dense irregular connective tissue and contains blood vessels, lymphatics, glands and nerve plexuses
Muscularis Externa
Composed of circular and longitudinal layers of smooth muscle with nerve plexuses in between layers. Responsible for muscle contraction to propel food through the digestive tract
Serosa/Adventitia
Outermost layer of the digestive tract
Serosa
When the outer layer is a serous membrane (a single layer of thin, flat cells that form a secrete lubricating fluid)
Adventitia
When the outer membrane is composed of loose connective tissue
Oral Cavity
The first part of the digestive tract. Composed of two parts 1. The vestibule and 2. Oral cavity proper
The vestibule
Space between the cheeks and lips and gums and teeth
Oral Cavity Proper
Other areas of the mouth
Palate
Makes up the superior border. It is divided into the hard palate (bone) and soft palate (muscle)
Uvula
The posterior extension of the soft palate
Deciduous Teeth
Two incisors, one canine (cuspid), two molars in each quadrant - 20 teeth in whole mouth
Permanent Teeth
Two incisors, one canine (cuspid), two premolars (bicuspid), three molars in each quadrant - 32 teeth
Tongue
A muscle associated with speech, taste and mechanical manipulation of food
Tongue Muscles
Made up of muscles that control the shape of the tongue (interinsic) and muscles that move the tonuge (extrinsic)
Frenulum
Inferior surface of the tongue which anchors the tongue and the floor of the mouth
Papille of the Tongue
Superior and lateral surfaces of the tongue are covered in papillae. Projections or bumps on the tongue. There are 4 types, some contain taste buds allowing the sense of gustation
Salivary Glands
Secrete digestive enzymes and mucus to help break down food while chewing
3 Major Salivary Glands
- Parotid 2. Submandibular 3. Sublingual
Parotid
Secretes serous (watery) fluid and is located anterior and inferior to the external ear opening
Submandibular
Secretes serous and mucous (viscous) fluid and is inferior to the mandible
Sublingual
Secretes mucus and is inferior to the tongue
Tonsils
Collections of lymphoid tissue found in areas of the pharynx. They play a role in the immune system
3 Tonsils
- Palatine 2. Pharyngeal 3. Lingual
Esophagus
Muscular tube extending from the pharynx to the stomach
Esophagys - Mucosa
Stratified squamous epithelium protects the esophagus from the friction as food travels from the oral cavity to the stomach
Esophagus - Submucosa
The mucus secreted is transported through a duct to be deposited in the lumen of the esophagus. The mucus will lubricate the tract to allow food to pass through easily
Esophagus - Muscularis Externa
This layer includes both smooth and skeletal muscle. Upper is skeletal. Middle is both and Lower is smooth
Esophagus - Serosa/Advenitia
Majority is covered by adventitia, composed of loose connective tissue
Stomach
A J shaped organ divided into 1. fundus 2. body 3. antrum
Antrum
Continuous with the first aspect of the small intestine known as the duodenum
Stomach Shape gives rise to what
Lesser and greater curvatures
Greater Omentum
a structure that hangs off the greater curvature of the stomach. It is an apron like structure that covers and protects the abdominal viscera
Stomach - Mucosa
Folded into ridges and folds called rugae. Non-permanent folds that allow the stomach to expand
Stomach Epithelium
Simple columnar and inwards folds extend down into the lamina propria to form gastric glands. The epithelium secretes mucus which helps protect the stomach from acids secreted by the gastric glands
Stomach - Submucosa
Contains blood vessels, lymphatics, lands and nerve plexuses which supply the stomach tissue with oxygen and control contraction of musculature
Stomach - Muscularis Externa
Three layers of smooth muscle arranged in different directions 1. outer longitudinal 2. middle circular 3. Inner oblique
Stomach - Serosa/Adventitia
covered by serosa
Intestines
Digested material travels from the stomach into the intestines, where it is further digested and eventually excreted from the body
Two Parts of Intestines
- small intestines 2. large intestines
Small Intestine Size and Location
6 m long and is divided into 3 portions, it is attached to the posterior abdominal wall
3 Portions of the small intestine
- duodenum 2. jejunum 3. Ileum
Duodenum
(25 cm) C-shaped and encloses the head of the pancreas
Jejunum
(2.5 m) most lies in the left upper quadrant of the abdomen
Ileum
(3.5 m) most lies in right lower quadrant of the abdomen
Small Intestine Mucosa - Villi
Finger like projections that extend into the lumen of the small intestine
Small Intestine Mucosa - Epithelium
Found on the villi, simple columnar with many absorptive cells whose apical surfaces have microvilli or a brush border
Why is a brush border important
it increases the surface area for the absorption of nutrients
Why are Goblet Cells between absorptive cells
they secrete mucus ro help lube the passage of food
Why are endocrine cells found in epithelium
secrete hormones involved in the regulation of satiety, blood sugar level and growth of eoithelial cells
Small intestine Mucosa - Lamina Propria
From the ore of each villus and contains blood capillaries and lymphatic capillaries.
Peyers Patches
Collections of lymphatic tissue located in the lamina propria - primarily abundant in ileum
Small Intestine Mucosa - Intestinal Glands
Deep folds of mucosa between the villi and secrete intestine juices
Small Intestine Mucosa - Plicae Circulates
Permanent transverse folds that help increase the surface area for absorption and causes the material to spiral through the small intestine
Small Intestine - Submucosa
Has duodenal (Brunner’s) glands that secrete alkaline mucus. This helps protect the small intestine from stomach acid that may be present in partially digested food after leaving the stomach
Small Intestine - Musclaris Externa
Two smooth muscle layers which are organized into circular and longitudinal layers
What is in between the small intestine’s muscularis externa layers
A nerve plexus
Small Inestine Serosa/Adventitia
Serosa
Large Intestine
Terminal portion of the digestive tract
Cecum
The first portion of the large intestine and has an extension off of it called the vermiform appendix
Ascending Colon
Extends from the cecum up to the right side of the abdomen to join the transverse colon just below the liver
Transverse Colon
Extends blow the liver, crossing the abdomen to join the decending colon below the spleen
Descending Colon
Extends down the left side of the abdomen from the splenic end of the transverse colon to the sigmoid colon
Sigmoid Colon
S shaped terminal portion of the colon that leads into the rectum
Rectum
Extends from the sigmoid colon into the anal canal, last portion of the large intestine, temporarily stores fecal matter before defecation
Anal Canal
Last portion of the digestive tract that leads into the external world
What does the Anal Canal Include
The anal column and internal and external anal sphincters
Anal Column
Longitudinal ridges in the canal
Internal and external anal sphincters
These maintain continence and relax to enable evacuation during defecation
