Ch 19 Digestive System Flashcards
How does the digestive system maintain homeostasis?
Maintains homeostasis by taking in food and water and then eliminating the waste products
Functions of the digestive system are carried out by the organs of the alimentarycanal or gastrointestinal tract (GI tract) and accessory organs
What are organs of the alimentary canal ?
Pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal
What are Accessory organs ?
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
What do salivary glands do?
Accessory organ
Secrete saliva, which contain enzymes that initiate breakdown of carbohydrates
What does mouth do?
alimentary canal
mechanical breakdown of food
chemical digestion of carbs begins
what does pharynx do ?
alimentary canal
connects mouth to esophagus
What does esophagus do?
alimentary canal
peristalsis pushes food to stomach
behind the trachea
What does stomach do?
alimentary canal
secretes acid and enzymes; mixes food with secretions to begin enzymatic digestion of proteins
What does small intestine do?
alimentary canal
mixes food with bile and pancreatic juice
final enzymatic breakdown of food molecules
main site of nutrient absorption
What does the large intestine do?
alimentary canal
absorbs water and electrolytes to form poop
What does rectum do?
alimentary canal
regulates elimination of poop
What is ingestion?
Function of digestive system
Eating and drinking
What is Secretion?
Function of digestive system
Saliva, water, acids, and enzymes enter the mouth and GI tract to help with the breakdown and absorption of foods.
What is Mixing and propulsion?
Function of digestive system
Move food along its way to the anal canal
What is Digestion?
Function of digestive system
Break down food into small molecules
Mechanical digestion begins in the mouth with the mastication of food.
Chemical digestion involves the further breakdown of food by the enzymes secreted by salivary glands, stomach, pancreas, and small intestine.
What is Absorption ?
Function of digestive system
Into the blood and lymph
takes place within the GI tract lumen by epithelial surface layer
What is Defecation
Function of digestive system
Elimination of wastes, indigestible substances, unabsorbed substances, water, some cells, and bacteria
Describe the mouth and its functions
Oral or buccal cavity
Takes in food and reduces its size through mastication
Starts the process of chemical digestion when saliva (has amylase) breaks down carbs
Boundaries are cheek, lips, hard/soft palate
What is the vestibule?
Space located between the lips and cheeks and the teeth
What is the oral cavity proper/
Space behind the teeth
What do the cheeks do?
Hold food in the mouth
Skin, adipose tissue, skeletal muscles, and an inner lining of moist nonkeratinized stratified squamous epithelium
What do lips do?
formed by Orbicularis muscle which closes the mouth
Fold of the mucous membrane called the labial frenulum that attaches the lips to the gingiva
What does the tongue do?
Made of skeletal muscle
Extrinsic muscles - attached to various bones such as the mandible and hyoid bone
Intrinsic muscles - change the shape and size of the tongue to assist with speech and swallowing
Held to the floor of the oral cavity by a fold of mucous membrane called the lingual frenulum (if too short - tongue tied or anklyoglossia)
On the dorsum (upper surface) of the tongue are many small projections called papillae (taste receptors and touch receptors)
Helps mix food and holds it between the teeth
Back of the tongue contains lymphatic tissue, called lingual tonsils, which destroy bacteria and viruses
What is the hard palate in the roof of the mouth?
Formed by the maxillary and palatine bones
Covered by a mucous membrane and stratified squamous epithelium
What is the soft palate in the roof of the mouth?
Posterior to the hard palate
Formed by muscle and is also covered by a mucous membrane
Separates the oral from the nasal cavity
What is the uvula?
Projecting off the posterior aspect of the soft palate
Prevents food and liquids from entering the nasal cavity during swallowing
What are the Lingual, palatine, and pharyngeal tonsils ?
protect the area from bacteria and viruses
Describe teeth
Incisors (most medial teeth), cut off food pieces
Cuspids (canines) are the sharpest teeth and they tear tough food
Premolars and molars are flatter, both are designed to grind food
Two sets of teeth
Primary or deciduous dentition (baby)
Secondary or permanent dentition (adult)
What are Salivary glands?
Secrete saliva, a mixture of water, enzymes, and mucus
Serous cells secrete a fluid made up mostly of water and also amylase
Mucous cells secrete mucus
Parotid, submandibular, and sublingual glands
What are serous cells?
cell in salivary gland
secrete a fluid made up mostly of water and also amylase
What are Mucous cells?
cell in salivary gland
secrete mucus
What is mass of mucous and serous cells?
Mass created by food mixed with the saliva and mucus mixture is called a bolus
What are parotid glands?
Salivary gland
largest ones
found under skin in front of ears
secrete serous saliva
What are submandibular glands?
Salivary gland
found on floor of mouth inside mandible
Secrete both serous and mucus
What are sublingual glands?
Salivary gland
smallest ones
under tongue
dry mouth - xerostomia
What is the Pharynx?
also known as the throat
Long, muscular structure
Extends from the area behind the nose to the esophagus
Connects the nasal cavity with the oral cavity for breathing through the nose
Composed of skeletal muscle
Lined with a mucous membrane
Pushes food into esophagus
What are the divisions of the pharynx?
Nasopharynx , behind the nasal cavity
Oropharynx , behind the oral cavity - part of both digestive and respiratory systems)
Laryngopharynx, behind the larynx- continues as the esophagus (part of both digestive and respiratory systems)
What is deglutition?
Swallowing - mostly a reflex
- Soft palate rises, causing the uvula to cover the opening between the nasal and the oral cavities
- Epiglottis covers the opening of the larynx
- Tongue presses against the roof of the mouth, forcing food into the oropharynx
- Muscles in the pharynx contract, forcing food toward the esophagus
- Esophagus opens
- Food is pushed into the esophagus by the muscles of the pharynx.
What is the esophagus?
Muscular tube that connects the pharynx to the stomach
Lies posterior to the trachea
Descends through the mediastinum in the thoracic cavity, through the diaphragm, and into the abdominal cavity
Opening in the diaphragm through which the esophagus passes is called the esophageal hiatus (where hernias occur)
1st section- skeletal muscle 2nd - mix of smooth and skeletal 3rd - smooth muscle
What is a hernia?
when organ pushes through a wall that contains it
What is Upper esophageal sphincter ?
Skeletal muscle and controls food entering the esophagus from the laryngopharynx
What is the Lower esophageal sphincter ?
Smooth muscle and controls food entering the stomach from the esophagus
What is Mucosa?
1st layer of GI tract
GI tract inner lining
Enzyme and mucus- secreting epithelial tissue
Very active in absorbing nutrients
What is submucosa?
2nd layer of GI tract
Areolar connective tissue, blood vessels, and a network of nerves called the submucosa plexus
Blood vessels that carry away absorbed nutrients
What is Muscularis?
3rd layer of GI tract
Smooth muscle, some areas also have skeletal muscle
Contracts to move materials through the canal
What is Serosa or peritoneum?
4th layer of GI tract
Outermost layer or adventita
Serous membrane with areolar connective tissue and simple squamous epithelium
Double-walled, outermost layer
Innermost wall is called the visceral peritoneum - keeps outside of SI moist
Outer layer is called the parietal peritoneum - abdominal lining
What is the stomach?
Below the diaphragm in the left upper quadrant of the abdominal cavity
Cardiac region-Attached to the esophagus (first portion)
Fundus-Superior to the cardiac region (2nd portion)
Does not absorb alot (only h2o, alcoholm fat soluble drugs) , the small intestine does the absorption
What is the pylorus?
Narrow portion connected to the small intestine
Pyloric sphincter controls the movement of substances from the pylorus of the stomach into the small intestine
What are rugae?
Numerous folds on the inner lining of the stomach
Help churn and mix the gastric contents
What are gastric glands?
Mucous cells secrete mucus to protect the lining of the stomach against the acidic pH.
Chief cells secrete pepsinogen, which is changed to pepsin in the presence of acid
Pepsip digests proteins .
What do parietal cells do?
Parietal cells secrete hydrochloric acid, which is necessary to convert pepsinogen to pepsin.
Secrete intrinsic factor, which is necessary for vitamin B 12 absorption
When a person smells food, the parasympathetic NS stimulates gastric glands
How are gastric glands stimulated?
by Gastrin produced by the stomach
What inhibits gastric glands?
Hormone cholecystokinin made by the small intestine
What is Chyme?
Mixture of food and gastric juices
Once chyme is well mixed, stomach contractions push small amounts into the small intestine a little at a time
4-8hours to empty stomach
Gastronomy tube can be put into stomach if you cant swallow - Ensure drink