**A&P 2 Unit 23 (Lab) [Digestive System] Flashcards
2 Components of the Digestive System
- Digestive Tract (Alimentary Canal)
- Accessory Organs
How does undigested food leave the system?
As feces.
4 Main Layers of the Digestive Tract (From Inside to Outside)
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa (Visceral Peritoneum)
Mucosa
Submucosa
Muscularis Externa
Serosa
3 Layers of the Mucosa (From Inside to Outside)
- A **Simple Columnar Epithelium **densely populated with goblet cells.
- A Lamina Propria Connective Tissue Layer containing blood & lymphatic vessels
- A Smooth Muscle Sheet called the Muscularis Mucosa
Mucosal Epithelium (Functions)
- Secretion of digestive substances
- Absorption of nutrients
Goblet Cells
Secrete mucus (a hydrated mucin protein), while other mucosal epitheial cells secrete digestive fluids & other substances such as water & salts
Enteroendocrine Cells of the Mucosa
Secrete hormones into the blood.
Absorption of Nutrients
Occurs through the mucosal epithelium & into either Capillaries (Most Nutrients) or Lacteal Lymphatic Vessels (Fats)
The mucosal epithelial cells are mitotically active…
…thus the epithelium is replaced approximately every 3 to 6 days
Double-Layered Muscularia Mucosa (Functions)
- To aid in digestion
- Absorption by moving the mucosal villi in the small intestine
The muscularis mucosa has both…
- Inner Circular & Outer Longitudial Fibers that function in moving the villi to aid in digestion & absorption.
- The fibers in the two layers are arranged at right angles to each other
Blood & lymph vessels as well as an intrinsic network of neurons (the _________) are located in the _______.
- Submucosal Plexus
- Submusoca
The Two Types of Movements Produced by Contractions of the Muscularis Externa
- Peristalsis
- Segmentation
Peristalsis
Wave-like contraction moving along the wall (Moving)
Segmentation
Alternate areas contract & relax (Mixing)
Myenteric Plexus
- Network of neurons in the muscularis externa
- It is in close communication with the submucosal plexus, and together, the two plexuses comprise the enteric nervous system.
The Outermost Layer of the Digestive Tract Wall
Serous fluiding-producing Serosa which both lubricates & reduces friction of the digestive tract within the ventral body cavity.
Ingestion occurs in the _____
Mouth
The Mouth
With its Stratified Squamous Epithelium, is involved in both Chemical & Mechanical Digestion
Bolus
A mass of food that has been chewed at the point of swallowing.
Transition in the esophagus wall
Striated (skeletal) to smooth muscle
Stomach (Functions)
- Chemical (Mostly proteins) Digestion
- Mechanical Digestion
- Storage of Food
4 Specialized Areas of the Stomach
- Cardia
- Fundus
- Body
- Pyloric (w/antrum)
3 Sheets of Muscle in the stomach’s Muscularis Externa
- Circular
- Longitudinal
- Oblique
Rugae
The stomach can expand greatly because of internal folds called rugae
Longitudinal Layer
Circular Layer
Oblique Layer
Chyme
- Once food is moxed with gastric juices in the stomach it is called chyme
- Which is then moved from the pylorus to the duodenum of the small intestine.
The majority of chemical digestion & virtually all-nutrient absorption occur in…
The Small Intestines
3 Regions of the Small Intestines
- Duodenum
- Jejunum
- Ileum
3 Modifications of the Inner Wall of the Small Intestine (& Functions) [From Macroscopic to Microscopic]
- Plicae Circularis (Circular folds)
- Villi
- Microvilli
Function to increase surface area of small intestine
The Intestines aid the body in its defense against pathogens by secreting…
…Antibacterial enzymes & antibodies (immunoglobulins) & by providing specialized sites in the ileum (lymphoid nodules called Peyer’s Patches) where leukocytes can fight pathogens
The large intestine absorbs…
- Water
- Salt
- Vitamins K & B
5 Parts of Large Intestine
- Cecum
- Appendix
- Colon
- Rectum
- Anal Canal
Appendix
Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum
Anal Canal
Taeniae Coli
Three bands of smooth muscle that cause the outer portion of the colon to be puckered into pockets called haustra.
Epiploic Appendages
Fat storage areas located on the outside of the colon
Brush Border
Formed by the microvilli of the small intestine’s epithelial cells
Anal Lining
Stratified Squamous Epithelium
Feces Composition
Indigestible food, bacteria, inorganic substances, and sloughed off epithelial cells from the digestive tract wall.
Sphincters (Functions)
Regulate the passage of food from one region of the digestive tract to the next and finally, out of the body as feces.
7 Sphincters of the Digestive Tract
- Upper Esophageal Sphincter (UES)
- Lower Esophageal Sphincter (LES)
- Pyloric Sphincter
- Ileocecal Sphincter or Valve
- Internal Anal Sphincter (IAS)
- External Anal Sphincter (EAS)
Upper Esophageal Sphincter (UES)
- Circular Skeletal Muscle
- Prevents air from entering the esophagus
Lower Esophageal Sphincter (LES)
- Physiological Sphincter
- Prevents acid reflux from the stomach into the esophagus
Pyloric Sphincter
- Circular Smooth Muscle
- Regulates passage of chyme from the stomach into the duodenum
Ileocecal Sphincter or Valve
- Circular Smooth Muscle
- Regulates passage of chyme from the ileum to the large intestine
Internal Anal Sphincter (IAS)
- Circular Smooth Muscle
- Under involuntary control
- When relaxed, it produces the urge to defecate
External Anal Sphincter (EAS)
- Circular Skeletal Muscle
- Under voluntary control
- When relaxed, it allows for defecation
3 Accessory Glands
- Salivary Glands (3 Pairs)
- Liver
- Pancreas
Salivary Glands
- Moisten food
- Cleanse & protect the mouth
- Produce amylase to begin enzymatic digestion of starch
Liver
- Produces bile, which emulsifies fats to increase their surface area for subsequent chemical digestion by lipases
- Bile is stored in & released from the gall bladder into the duodenum
Pancreas
- Main digestive enzyme-producing exocrine organ in the body
- It releases a host of digestive enzymes into the duodenum via the pancreatic duct
- It also produces bicarbonate to neutralize the chyme from the stomach
