Digestive System Flashcards
Learn the digestive system part 1
what are the main functions of the digestive system?
- Take in food (ingestion)
- break it into absorbalbe nutrient molecules (digestion)
- absorb molecules into the blood stream (absorption)
- rid body of indigestible remains (excretion)
Organs of the digestive system fall into 2 groups. What are the names of those groups?
- Alimentary canal (GI tract)
- Accessory organs
Alimentary Canal
- continuous muscular tube that runs from mouth to anus
- digests food
- absorbs fragments through lining in blood
- excretes waste
What are the Accessory organs?
- Teeth
- tongue
- gallbladder
- Digestive glands: produce secretions that break down food (salivary glands, liver, pancreas)
- Ingestion
taking food into mouth
- Mastication
chewing food and mixing it with saliva
- Peristalsis (Motility)
rhythmic wave-like contractions that move food through GI tract
- Deglutition
swallowing food
- Digestion
Mechanical or chemical breakdown of foods
- Secretion
release enzymes, water, and buffers into GI tract
- Absorption
moving nutrients (monomers) into the body
- Defecation
excretion of waste products
Give a good breakdown of Peristalsis
- coordinated muscle contraction and relaxation
- wavelike movements
- food bolus moves forward
Give a good breakdown of segmentation
- simultaneous muscle contractions
- back and forth movements
- food bolus gets mixed with digestive secretions
Mechanical Digestion
- begins in the oral cavity
- doesn’t break chemical bonds
- increases surface area for chemical digestion
Chemical digestion
- Begins in oral cavity but peaks in the stomach and small intestine
- carried out by enzymes
- breaks chemical bonds to generate small molecules from large molecules
________ and _________ are the last of the major digestive processes
secretion and absorption
Secretion
- movement of substance from cells into the lumen
- secretion of HCl into stomach to promote digestion
Absorption
- movement of substance from the lumen to cells
- Highly selective process, specific substances absorbed in different G.I. regions
Histological Organization (4 tissue layers)
- Mucosa (epithelium)
- Submucosa (connective tissue, nerves, blood vessels)
- muscularis externa (circular layer and longitudinal layer of smooth muscle)
- serosa (connective tissue, continuous with mesentery)
Study the digestive tract four layers slide
don’t rate this a 5 actually go look at it.
- Mucosa
- layer that lines lumen
- functions: different layers perform one or all three
: secretes mucus, digestive enzymes and hormones
: absorbs end products of digestion
: protects against infectious disease
- Submucosa
- consists of areolar connective tissue
- contains blood and lymphatic vessels, lymph nodes
-secretions
- Muscularis externa
- smooth muscle layer responsible for peristalsis and movement of bolus through GI tract
- contains inner circular muscle layer and outer longitudinal layers (circular layer thickens in some areas to form sphincters)
Enteric Nervous System
- the GI tract’s own nervous system (gut brain)
- contains more neurons than the spinal cord
- major nerve supply to muscularis externa that controls motility
- Serosa
- outermost layer, made up of visceral peritoneum
- formed from connective tissue
- replaced by fibrous adventitia in esophagus (dense CT that hods esophagus to surrounding structures)
Functions of the oral cavity
- protection against physical and chemical abrasions, pathogens
- mechanical digestion: increases surface area using teeth, tongue, and palate
- Lubricating food with saliva
- chemical digestion begins with enzymes in saliva
The palate forms the roof of the mouth and has two distinct parts:
- hard palate: formed by maxillae bone
- Soft Palate: soft tissue formed by mostly of skeletal muscle
What does the soft palate do?
- closes off nasopharynx during swallowing
Uvula
fingerlike projection that faces downward from free edge of soft palate
The tongue
- composed of interlacing buncles of skeletal muscle
- Functions:
- gripping, repositiong, mixing of food
- formation of bolus, (food and salive)
- initiation of swallowing
- speech
- taste reception
What are the features of mastication
- mechanical digestion
- increases surface area
- mixes food with saliva
There are three paired ______ _______ _______ located outside the oral cavity that produce saliva
major salivary glands
What are the major salivary glands
Parotid, submandibular, and sublingual
Parotid gland
- anterior to ear
- parotid duct opens into oral cavity next to 2nd upper molar
Submandibular gland
- medial to body of mandible
- duct opens at base of lingual frenulum
Sublingual
- anterior to submandibular gland under tongue
- opens via 10-12 ducts into floor of mouth
Saliva
- 1-1.5 liters produces each day
- 99.4 percent water and mucus
- secretion stimulation by facial and glossopharyngeal nerves (autonomic cranial nerves) in response to varied stimuli
- cleanses mouth, contains lysozyme (antimicrobial)
- dissolves food chemicals for taste
- begins chemical digestion of starch with enzyme amylase
