Digestive System Flashcards
The Digestive System
• General anatomy and digestive processes
• Mouth through esophagus
• Stomach
• Liver, gallbladder and pancreas
• Small intestine
• Chemical digestion and absorption
• Large intestine
Digestive Functions:
• Ingestion - intake of food
• Digestion - breakdown of molecules
• Absorption - uptake nutrients into blood/lymph
• Defecation - elimination of undigested material
Stages of Digestion:
- Mechanical digestion
- Chemical digestion
Mechanical Digestion
physical breakdown of food into smaller particles (churning - pag nguya) using teeth and tounge
Results of Chemical digestion:
• polysaccharides into monosaccharides
• proteins into amino acids
• fats into glycerol and fatty acids
Chemical Digestion
series of hydrolysis reactions that break macromolecules into their monomers
- enzymes from saliva, stomach, pancreas and intestines
Digestive Processes:
- Motility - muscular contraction that break up food, mix it with enzymes and move it along
- Secretion - digestive enzymes and hormones
- Membrane Transport - absorption of nutrients
digestive enzymes and hormones:
- amylase - breaks down starch (mouth)
- pepsin - breaks down proteins available in food (stomach)
- lipase - breaks down fats/lipids (small intestine glands)
Digestive tract (GI tract)
30 foot long tube extending from mouth to anus
Accessory organs:
teeth, tongue, liver, gallbladder, pancreas, salivary glands
Tissue Layers of GI Tract:
- Mucosa: epithelium, lamina propria, muscularis mucosae
- Submucosa: esophageal glands
- Muscularis externa: inner circular layer, outer longitudinal layer
- Adventitia or Serosa: areolar tissue or mesothelium (serosa covers most of the GI organ, acts as protective coat)
Inner Circular Layer and Outer Longitudinal Layer
Inner Circular Layer: they constrict the lumen aids in mixing
Outer Longitudinal Layer: helps in the peristalsis
Enteric Nervous Control
- Second brain of GI tract
- Able to function independently of central nervous system (CNS)
two nerve networks of Enteric Nervous Control:
Submucosal Plexus:
- controls glandular secretion of mucosa
- contractions of muscularis mucosae
Myenteric Plexus:
- controls peristalsis
- contractions of muscularis externa
- __________ of small intestines holds many blood vessels
- ________ anchors colon to posterior body wall
Mesentery and Mesocolon
connects/attaches stomach to liver
Lesser Omentum
covers small intestines like an apron
Greater Omentum
short myenteric reflexes (swallowing)
Neural Control
messengers diffuse into bloodstream, distant targets
Hormones
messengers diffuse to nearby target cells
Paracrine secretions
keep food between teeth for chewing; essential for speech and suckling in infants
Cheeks and lips
space between teeth and cheeks
vestibule
_______ - cutaneous area versus ________ - red area
Lips
Vermilion
- a muscular manipulator of food
- papillae and taste buds on the dorsal surface
- lingual glands secrete saliva, tonsils in root
Tongue
- allow breathing and chewing at the same time
- palatoglossal and palatopharyngeal arches
Hard and soft palate
baby teeth
adult teeth
20
32
Tooth Structure
- The periodontal ligament is modified periosteum
- Cementum and dentin are living tissue
- Enamel is a noncellular secretion formed during the development
- Root canal leads into the pulp cavity
Gingiva or gums
Breaks food into smaller pieces to be swallowed
Mastication or Chewing
function of Saliva:
- moisten
- begin starch and fat digestion
- cleanse teeth
- inhibit bacteria, bind food together into the bolus
Small intrinsic glands found under mucous membrane of mouth, lips, cheeks and tongue - secrete at constant rate
Salivary Glands
3 pairs extrinsic glands connected to oral cavity by ducts:
- parotid gland - largest
- submandibular gland
- sublingual gland
Mucous cells secrete _______
Mucus
Serous cells secrete ____________
thin fluid rich in amylase
salivary glands produce thin saliva, rich in enzymes
parasympathetic stimulation
produce less abundant, thicker saliva, with more mucus
sympathetic stimulation
Higher brain centers stimulate salivatory nuclei so sight, smell and thought of food cause __________
Salivation
Pharynx
- Skeletal muscle
- deep layer – longitudinal orientation
- superficial layer – circular orientation
- superior, middle and inferior pharyngeal constrictors
Straight muscular tube 25-30 cm long
Esophagus
Series of muscular contractions coordinated by center in medulla and pons
Swallowing (Deglutition)
tongue collects food and pushes it back into oropharynx
Buccal phase
- soft palate rises and blocks nasopharynx
- infrahyoid muscles lift the larynx; epiglottis folded back
- pharyngeal constrictors push bolus down the esophagus
Pharyngeal-esophageal phase
Mechanically breaks up food, liquifies food and begins chemical digestion of protein and fat
Muscular sac (internal volume from 50ml to 4L)
Stomach
opening to duodenum
Pylorus
domed portion superior to esophageal opening
fundus
main portion of organ
Body
narrow inferior end
pyloric region
Pylorus is a thick ring of smooth muscle that forms a __________
sphincter
- simple columnar glandular epithelium
- lamina propria is filled with tubular glands (gastric pits)
Mucosa
Muscularis externa has 3 layers:
- outer longitudinal layer
- middle circular layer
- inner oblique layer
