Textbook Notes (270,000)
CA (160,000)
Chapter 15

SCIE 22273 Chapter Notes - Chapter 15: Lingual Tonsils, Gastrointestinal Tract, Gastric Glands

Faculty of Applied Health and Community Studies
Course Code
SCIE 22273
Tara Hayes

of 12
Chapter 15 Digestive System
Digestion: mechanical and chemical breakdown of foods and the absorption of
the nutrients from it
Mechanical digestion breaks larger foods into smaller one
But it does not alter the chemical composition
Chemical digestion breaks foods into simpler form
General characteristics of the alimentary canal
The alimentary canal is a muscular tube that passes through the thoracic and
abdominopelvic cavities
The structure of the wall
The alimentary canal consists of 4 distinct layers
1. Mucosa/ mucous membrane:
- innermost layer
- In some regions, it consists of lumen (lumen helps increase
surface area)
-It protects tissues beneath it and carries on secretion and
2. Sub mucosa:
-Its vessels nourish tissues and carries away absorbed materials
3. Muscular layer:
-Provides movement of tube
-Has 2 coats of smooth muscle tissue
-When the circular fibers contract, the tube’s diameter decrease
-When the longitudinal fiber contracts, it shortens
4. Serous layer
-Protects underlying tissues and secretes serous fluid, which
moistens outer surface
Movement of the tube
2 major types of movements: 1. Mixing movement 2. Propelling movement
Propelling movement : peristalsis
Peristalsis moves food along the tube
Begins digestion by mechanically breaking food and mixes it up with saliva
This process is called mastication
Narrow space between lips, teeth and cheek is called the vestibule
Mucous membrane covers the tongue
Lingual frenulum attaches the tongue to the floor of the mouth
Papillae on tongue provide friction, which helps to handle food
find more resources at oneclass.com
find more resources at oneclass.com
Papillae also contain taste buds
Root of the tongue is covered with lingual tonsils
Palate consists of : hard and soft
The soft extends downwards as a cone-shaped projection: uvula
At the back are masses of tissues (lymphatic) called palatine tonsils
These help body against infection
2 different sets of teeth are formed
1. Primary teeth / deciduous
-Erupt through gums between 6 months and 2-4 years
-There are 20 of these, 10 on each jaw
2. Secondary teeth /permanent
-Push primary teeth out of the sockets
-Consists of 32, 16 on each
-Start at 6 years, but not complete until 17-25 years
Mechanical digestion increases surface area
Each tooth consists of a crown and root
Enamel covers the tooth
It consists of calcium salts and is the hardest in the body
Beneath enamel, the dentin covers the pulp
Cementum (bone-like material) covers the root
Salivary Glands
Secrete saliva
Salivary secretions
2 types of secretory cells :
1. Serous cells
-Produces fluid that contains salivary amylase
-Can split starch and glycogen
2. Mucous cells
-Secretes mucus
-Binds food and lubricates swallowing
Parasympathetic secretes large volumes of saliva when a person sees, smells
or tastes food
Major Salivary Glands
3 major types:
1. Parotid :
-Largest glands of the major ones
-Secrete fluid rich in salivary amylase
2. Submandibular gland:
find more resources at oneclass.com
find more resources at oneclass.com
-Secrete more viscous fluid than the parotid
3. Sublingual :
-Primarily mucus type fluid
Pharynx and Esophagus
Neither digest food, but are important passageways
Structure of pharynx
Pharynx connects the nasal and oral cavity to the larynx and esophagus
3 parts:
1. Nasopharynx : provides passage for breathing
2. Oropharynx : passage for moving food from mouth
3. Laryngopharynx : passage for esophagus
Swallowing mechanism
3 stages for swallowing:
oStage #1
-Food chewed and mixed with saliva
-Tongue rolls this bolus and forces it in oropharynx
oStage #2
-Food palate and uvula raise up
-Hyoid and larynx elevate
-Tongue presses against oral cavity scaling off oral cavity
-Longitudinal muscles in pharyngeal contract
-Muscles in laryngopharynx relax (opens epilglottis)
-Peristaltic waves move food along
oStage #3
-Peristalsis transport food to stomach
Tube that goes from the pharynx to the stomach
Has capacity of 1 liter or more
Initiates protein digestion
Receives food from the esophagus, and moves it to the small intestine
Parts of the stomach
Divided into:
1. Cardia – small area near esophagus
2. Fundus – temporary storage area
3. Body – main part of the stomach
4. Pylorus
The pyloric spincter controls gastric emptying
Gastric secretions
find more resources at oneclass.com
find more resources at oneclass.com