Digestion
The mechanical and chemical breakdown of foods and the absorption of the resulting nutrients by cells
Digestive system
Consists of organs that mechanically and chemically digest food
Alimentary canal
- The path food takes from the mouth through the anus
- includes mouth, pharynx, esophagus, stomach, small intestines, large intestines, rectum, and anus
- includes accessory organs of the salivary glands, liver, gall bladder, and pancreas
1. Mucosa
2. Submucosa
3. Muscular layer
4. Serosa
What 4 layers make up the alimentary canal?
Mucosa or mucous membrane
Surface epithelium, underlying connective tissue, and a small amount of smooth muscle form this layer
Lumen
- The internal passageway of the alimentary canal, folded with tiny projections that extend into the passageway of the digestive tube
- folds increase the absorptive surface area
Submucosa
- Contains considerably loose connective tissue as well as glands, blood vessels, lymphatic vessels, and nerves
- it's vessels nourish surrounding tissues and carry away absorbed materials
Muscular layer
This layer, which provides movements of the tube, consists of two coats of smooth tissue
-circular fibers: decrease the diameter
- longitudinal fibers: decreases the length
Serosa or serous layer
- Layer of epithelium on the outside and the connective tissue beneath compose the serous layer, or outer covering of the tube
- produces serous fluids allows the organs to slide freely over each other
Segmentation
In the small intestine , a process that aids mixing by alternately contracting and relaxing the smooth muscle in nonadjacent segments of the organs
Peristalsis
- Propelling movements include a wavelike motion
- a ring of contraction occurs in the wall of the tube
Mouth
Receives food and begins digestion by mechanically breaking up solid particles into smaller pieces and mixing them with saliva
Cheeks
Forming the lateral walls of the mouth, consists of outer layers of skin, pads of subcutaneous fat, muscles associated with expression and chewing, and inner linings of moist, stratified squamous epithelium
Lips
- Highly mobile structures that surround the mouth opening
- they contain skeletal muscles and sensory receptors useful in judging the temperature and texture of foods
Tongue
- Nearly fills the oral cavity when the mouth is closed
- Connected to the floor of the mouth via the lingual frenulum
Lingual frenulum
A membranous fold connects the midline of the tongue to floor of the mouth
Papillae
Rough projections on the tongue surface provide friction, which helps handle food
Lingual tonsils
Posterior of the tongue is anchored to the hyoid bone and is covered with rounded masses of lymphatic tissue
Palate
Forms the roof of the oral cavity and consists of a bony anterior part (hard) and a muscular posterior part (soft)
Uvula
A muscular arch of the soft palate extends posteriorly and downward as a cone shaped projection
Palatine tonsils
- Masses of lymphatic tissue in the back of the mouth, on either side of the tongue and closely associated with the palate
- structures lie beneath the epithelial lining of the mouth and, like other lymphatic tissues, help protect the body against infecti
Pharyngeal tonsils
Masses of lymphatic tissue (also known as adenoids) are on the posterior wall of the pharynx, above the border of the soft palate
Teeth
Two different sets form during development, begin mechanical digestion by breaking pieces of food into smaller pieces
Salivary glands
Secrete saliva, fluid moistens food particles, help bind them, and begins the chemical digestion of carbohydrates
Serous and mucous
What are the 2 types of salivary secretion cells?
Salivary amylase
Serous cells produce a watery fluid that contains this digestive enzyme, splits starch and glycogen molecules into disaccharides� the first step in the chemical digestion of carbohydrates
Mucus
Thick liquid which binds foods and particles and acts as a lubricant during swallowing
1. Parotid
2. Submandibular
3. Sublingual
What are the 3 major salivary glands?
Parotid gland
- Largest of the major salivary glands
- Secretory cells are primarily serous cells
- These glands secrete a clear, watery fluid that is rich in salivary amylase
- lie just inferior of each ear
Submandibular glands
- Located in the floor of the mouth on the inside surface of the lower jaw
- equally serous and mucus
- secrete a more viscous fluid than the parotid gland
Sublingual glands
- Smallest of the salivary glands, are on the floor of the mouth inferior to the tongue
- their secretory cells are primarily the mucous type, making their secretions thick and stringy