A&P 2 (Digestive System)

Digestive System
is the mechanical and chemical breakdown of foods into forms that cell membranes can absorb.

Mechanical Digestion
Breaks large pieces into smaller ones with altering their chemical composition

Chemical Digestion
Breaks food into simpler chemicals. The organs of the digestive system carry out these processes, as well as ingestion, propulsion, absorption, and defecation

Alimentary canal
A muscular tube that moves food. Extends form the mouth to the anus, and several accessory organs, which release secretions into the canal. It includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine and anal canal

Where does the digestive system originates from?
The inner layer (endoderm) of the embryo

Segmentation
cycles of contraction that churn and fragment the bolus, mixing the contents with intestinal secretions.

Peristalsis
Wavelike motion that propels food bolus forward in the digestive tract

submucosa
Loose connective tissue
blood vessels
lymphatic vessel, nerves
Nourishes surrounding tissues
Transports absorbed materials

Muscular Layer
Smooth Muscle fibers in circular and longitudinal groups
Movement of the tube and its contents

Serosa (Serous Layer)
Provides lubrication
Protection
Reduces Friction

Layers of the Wall of the Alimentary Canal
1. Mucosa
2. Submucosa
3. Muscular layer
4. Serosa

Mucosa
Provides movements of the tube
Protection
Secretion
Absorption

Salivary Amylase
Enzyme that splits starch and glycogen molecules into disaccharides.

What does mucus do during swallowing
Binds food particles and acts as a lubricant during swallowing.

What stimulates the salivary glands to secrete saliva?
Parasympathetic impulses that secrete large volume of watery saliva when a person smells, taste, or even thinks about pleasant foods

Major Salivary Glands
1. Parotid
2. Submandibular
3. Sublingual

Parotid Glands
Largest of the major salivary glands.
Clear, watery serous fluid, rich in salivary amylase.
Some serous fluid with some mucusmore viscous than parotid secretion

Submandibular Glands
A Gland in the floor of the mouth on the inside surface of the lower jaw.

Sublingual Glands
The smallest of the major salivary glands. Primarily thick, stringy mucus

How many stages does the swallowing mechanism have
Three stages

1st Stage of swallowing
Food is chewed and mixed (voluntary). The tongue rolls this mixture into a mass, or bolus, and forces it into the pharynx.

2nd Stage of swallowing
Swallowing begins as food reaches the pharynx and stimulates the sensory receptors around the pharyngeal opening. This triggers the swallowing reflex

3rd Stage of swallowing
The swallowing reflex momentarily inhibits breathing. Then during the third stage of swallowing. peristalsis transports the food in the esophagus to the stomach

Palate
Palate The palate forms the roof of the oral cavity and consists of a hard anterior part and a soft posterior part.

Teeth
The teeth are the hardest structures in the body, but they are not part of the skeletal system, because they contain at least two types of proteins that are not also found in bone, and their structure is different

Tongue
1. Located in the Floor of the Mouth
2. Mixes food with saliva; moves food toward pharynx; contains taste receptors

Stomach
The stomach is a J-shaped, pouchlike organ, about 25-30 centimeters long, which hangs inferior to the diaphragm in the upper left portion of the abdominal cav- ity. It has a capacity of about one liter or more, and its inner lining is marked by thick folds (rugae) of the mu- cosal and submucosal layers that disappear when its wall is distended. The stomach receives food from the esophagus, mixes it with gastric juice, initiates the digestion of proteins, carries on a limited amount of absorption, and moves food into the small intestine.

Parasympathetic
Everyday normal functions of the digestive system

Sympathetic
Deals with Stress

Autonomic Nervous System
Involuntary

Somatic Nervous System
Voluntary

Enzymes Catalyst
Lowers the temperature for a reaction to take place.

Endocrine Gland
Hormones goes to the blood stream. Hormones has a receptor

Example of a Hormone
Insulin

Exocrine
Enzymes has a duct and goes to the site of action (local)

Digestive system
Starts at the mouth ends with the anus

Layers of the digestion system
1.
2.
3.
4.

Mucosa
The inner lining. The main function is absorption, secretion, Protection

General Function of the direction tract
1. Ingestion: In take of food and liquid
2. Mechanical Processing (Chewing)
3. Digestive (chemical Processes)
4. Secretions Hormones, Enzymes
5. Absorption (Body takes in nutrients)
6. Compaction removing of water to create feces) Dehydrations and elimination of organic waste

Viscera
Inner organs. Need to slide past each other in the abdominal cavity

Accessory organs of the digestive tract
Critical for digestion but not apart of the tract itself and they are:
1. liver
2. Salivary Glands
3. Gallbladder
4. Pancreas

How many pairs of Salivary glands do we have
3, 6 in total.
1. Parotid
2. Submandibular
3. Sublingual

How does food move up until the food gets into the smooth muscles
Gravity moves food

Reasons for chewing
1. Break down
2. Increase surface area gives more areas for enzymes to attack food

Layers of the digestion system
1.
2.
3.
4.

How is the bile duct formed
It is formed by the union of the common hepatic and cystic ducts.

Functions of Bile Salts
The functions of bile salt is to reduce surface tension and break fat glubules into droplets. Bile Salts also enhance the absorption of fatty acids and cholesterol.

Emulsification
The process by which surface tension is reduced and fat glubules are broken up into droplets

Small Intestine
a tubular organ that extends from the pyloric sphincter to the beginning of the large intestine. Receives secretion from the pancreas and liver, absorbs products of digestion, and transports the remaining residue to the large intestine.

Regulation of bile salt
The production of bile salt starts when Cholecystokinin enters the gallbladder to contract

Mastication
mechanically breaking up the solid particles into smaller pieces and mixing them with saliva.

Frenulum
Membranous fold in the mouth

Papillae
Rough projections of the tongue
Can provide friction which helps handles food.

Does the esophocus have any digestive activity?
No

Does the large intestine have any digestive activity?
No

What is the PH of the stomach?
1 – 2. This is because of hydrochloric acid

What is the enzymes of the stomach
Pepsin

What is the PH of the mouth?
8

Pepsin
Enzyme of the Stomach
Take proteins and breaks them down into polypetides.

Caffeine
Absorbed at the level of the stomach

Aspirin
(IBprofen, Naproxen) Never take on an empty stomach. It will cause an ulcer (erosion of the stomach lining).

Duodenum
Upper part of the small intestines

What is the only enzyme that works at an acidic PH?
Pepsin (it only works in an acidic PH)

Sodium Bicarbonate
Comes from the pancreas
Act as a buffer.

What are the functions of the pancreas
Endocrine
Exocrine

What are the pancreatic enzymes
1. Pancreatic Amylase
2. Pancratic Lipase
3. Trinson, Chymotripson (Work on polypeptides)
4. Carboxypeptidase (peptides)
5. Nuclease (works on nucleic acids)

Where are proteins broken down at
In the stomach

What cells produce hydrochloric acid
Parietal Cells

Does digestion occur in the small intestine
No

Why does mucus line the walls of the stomach
so the hydrochloric acid doesn’t damage the walls of the stomach

Helicobacto Pilori
Bacteria that casuses ulcers

Gastrin
Hormone
produced by the walls of the stomach. Gos to the blood stream. Produced when food enters the stomach.

Intrinsic Factor
Has to do with recovering vitamin B12 from food. Intrinsic factor are located in the parietal cells.

How much gastic juice does the stomach produce each day?
1500 ml

Food that is mixed is called
chyme. When food comes from the stomach to the small intestines

What is the ultimate result you want to achieve when food enters the body?
to break down substances into glucose and amino acids

What is the function of the appendix
The appendix doesn’t have a function

Where does Ecoli found in the body
Ecoli lives in the large intestine. You get ecoli from your mother. Helps us with vitamin K.

Functions of the large intestine
The function of the large intestine is the reabsorb water

Intestinal Enzymes
Peptidase
Sucrase
Intestinal Lipase
Enterokinase

Peptidase
Breaks down peptides to amino acids

Sucrase
maltase lactase (disaccharides)

Intestinal Lipase

Enterokinase
Breaks down trysinogen for trysin to become available

Primary function of small intestine
To absorb nutrients

Lactles
lymphatic vessels, where fatty acids are absorbed

Glucose & amino acids
Goes into the blood stream glucose is stored as glycogen (Storage factor)

Portal Vein
Takes amino acids & glucose to the liver

What are the 3 part of the small intestines
1. duodenum
2. jejunum
3. ileum

Jejunum
2 layer of the small intestines. It is where most of the digestion and absorption nutrients occurs

illeum
The first segment of the small intestine. It is also the longest, it averages about 3.5 meters in length

Pepsinogen
Inactive for of Pepsin. Turns into pepsinogen when it comes in contact with hydrochloric acid

Pyloric Sphincter
valve that controls gastric emptying

Parietal Cells
Secrete Hydrochloric Acid

Chief Cells
Secrete digestive enzymes

Gastric Juices
The enzymes and hormones produced by the Chief Cells, Parietal Cells and Mucous Cells. The product of Mucous Cells, Chief Cells and Parietal Cells

Pepsin
Enzyme that is secreted by Chief Cells and is the most important. It is secreted as an inactive, nonerosive enzyme precursor called pepsinogen. Begins digestion for nearly all proteins

Parts of the Stomach
1. The Fundic Region (Fundus) (Upper Portion)
2. The Cardiac Region (Cardia) (Middle Portion)
3. The Pyloric Region (Pylorus) (Lower Portion)

esphageal sphincter
1. Muscle Fibers
2. Closes the entrance to the stomach, this prevent regurgitation of the stomach contents into the esophagus.

The Cephalic Stage of Gastric Secretion
The sight, taste, smell, or thought of food triggers parasympathetic reflexes. Gastric juice is secreted in response.

The Gastric Stage of Gastric Secretion
Food in stomach chemically and mechanically stimulates release of gastrin, which, in turn, stimulates
secretion of gastric juice; reflex responses also stimulate gastric juice secretion

The Intestinal Phase of Gastric Secretion
as food enters the small intestine. It simulates intestinal cells to release intestinal gastrin, which, in turn, promotes the secretion of gastric juice from the stomach wall

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