Module 3 - Digestive System Flashcards
Boundaries of the oral cavity
Roof
- hard palate: separates mouth from nasal cavity
- soft palate: separates mouth from pharynx
Anterior boundary
- lips: orbicularis oris muscle, vermillion border
- teeth
Lateral boundary
- cheeks: buccinator muscles
- teeth
Floor
- tongue
Intrinsic (minor) salivary glands
secrete saliva directly into the mouth
- lingual
- palatoglossal
- palatal
- buccal
Extrinsic (major) salivary glands
secrete saliva into the mouth via a series of ducts
- parotid
- submandibular
- sublingual
Parotid duct
the duct of the parotid gland that runs forward and pierces the buccinator muscle to empty into the mouth
Saliva
a fluid consisting of water, mucus, digestive enzymes, and antibodies that aids in chemical digestion and lubrication
- salivation can be triggered by taste and smell
Muscles of mastication and their actions
Temporalis - elevate mandible
Masseter - elevate mandible
Lateral pterygoid - depresses chin; moves jaw side-to-side
Meidla pterygoid - grinding motion
Tongue
surface covered in papillae that contain taste buds
- forms a bolus for swallowing
Intrinsic tongue muscles
originate from hyoid bone
responsible for intricate shape changes required for speech
- superior longitudinal muscle
- transverse lingual muscle
- vertical lingual muscle
Extrinsic tongue muscles
most of the tongue
attach to the bones of the cranium, the hyoid bone, and the mandible
Responsible for strong movements necessary for swallowing
- genioglossus
- hyoglossus
- styloglossus
- palatoglossus
Two sets of teeth
deciduous teeth - 20 baby teeth ages 1-2
permanent teeth - 32 adult teeth ages 6-20
Incisors (teeth)
chisel shaped teeth adapted for cutting
- central and lateral
- ONE ROOT EACH
Canines (teeth)
pointed teeth adapted for piercing
- ONE ROOT EACH
Premolars (teeth)
circular teeth with two cusps adapted for tearing
- most have one root
- first maxillary premolar which has TWO ROOTS
- NO PREMOLARS IN DECIDUOUS TEETH
Molars (teeth)
large teeth with four or five cuspids adapted for crushing
- mandibular molars have TWO roots
- maxillary molars have THREE roots
- 3rd molars are the wisdom teeth
Parts of a tooth
Crown
Neck
Root
Pulp Cavity
List the four basic tissues of teeth (hardest to softest)
Enamel
Dentin
Cementum
Pulp
Enamel
covers the dentin of the crown
- hardest substance in the body
Dentin
hard tissue that makes up most of the tooth; deep to the enamel ad cementum
Cementum
tough yellow tissue covering the root
- periodontal fibers embedded within
Pulp
soft tissue within the pulp cavity containing the nerves and blood vessels that nourish the dentin
What is the difference between dentin/cementum and enamel
Dentin and cementum can regenerate and self-repair, but enamel CANNOT
Pharynx (and parts)
a U-shaped structure connecting the oral and nasal cavities to the esophagus
Nasopharynx - highest posterior to nasal cavities
Oropharynx - middle, posterior to oral cavity
Laryngopharynx - lowest, POSTERIOR TO LARYNX
Esophagus
continuation of the pharynx at C6 that empties into the stomach inferiorly
Peristalsis
involuntary muscle contractions that move food into the stomach from the esophagus
Pharyngeal constrictor muscles
muscles making up the pharynx wall that constrict to push food into the esophagus
What muscle structures are involved in swallowing?
tongue, soft palate, pharynx, larynx, esophagus
What comes into contact with the soft palate during swallowing?
nasopharynx junction
What structure moves downwards to block the nasal cavity and larynx?
Epiglottis
Buccal Phase of swallowing
The VOLUNTARY actions of mastication and bolus-formation with the tongue and hard palate with saliva
Pharyngeal Phase of swallowing
Larynx and pharynx move forward and elevate, and the epiglottis tilts downwards to close the entrance to the larynx, preventing food from entering the lower respiratory tract
- BREATHING IS INTERRUPTED
- the vagus nerve triggers a cough if a substance does enter the larynx
Esophageal Phase of swallowing
peristaltic waves propel the bolus down the esophagus until it reaches the lower esophageal sphincter, which relaxes to allow the bolus to enter the stomach
- BREATHING RESUMES when bolus reaches upper esophagus
Stomach
major site of digestion
secretes gastric juice
Gastric juice
a mixture of water, mucus, HCL, intrinsic factor, and the enzyme pepsinogen that aids in chemical digestion
- made of secretions from three cell types: parietal, chief, and neck mucous cells
Parietal cells produce…
hydrochloric acid
Chief cells produce…
digestive enzymes; pepsinogen and gastric lipase
Gastric lipase
breaks down lipids into fatty acids and monoglycerides
Pepsin
active form of pepsinogen
Neck mucous cells produce…
mucus that protects the stomach lining from hydrochloric acid and digestive enzymes
Accessory Glands of Digestive System
pancreas, liver, gallbladder
Pancreas
both exocrine and endocrine functions
- 99% of cells are exocrine secreting pancreatic juice
Cells of the acini
secrete pancreatic juice to neutralize stomach acid and help the digestion of protein, carbohydrates, and lipids
- exocrine
Islets of Langerhans
secrete insulin and glucagon hormones that regulate blood sugar levels
- endocrine
Liver (lobes)
largest gland in the body made of 4 lobes:
right, left, caudate, quadrate
4 main liver functions
- produce bile, urea, heparin, vitamin A, plasma proteins, and antibodies
- metabolize fats, amino acids, sugars, and toxins
- storage unit for fats, vitamins A, D, and 12, iron, and glycogen
- Activation of vitamin D
Coronary ligaments
surround the BARE AREA of the liver that lacks a peritoneum and is in direct contact with the diaphragm
Bile
greenish-yellow alkaline liquid that is synthesized by the liver and stored in the gallbladder
- emulsifies fats by increasing surface area
- stimulates peristalsis
- channel for excretion of toxins
Bile is secreted by ____ and released into the _____
hepatocytes; duodenum via common bile duct)
Bilirubin
a yellow pigment produced by the breakdown of the heme group of hemoglobin
- principal pigment in bile
- broken down and excreted as feces by large intestines
Bilirubin is secreted into bile that goes into the small intestine via the …
biliary tree
Principal organ responsible for drug excretion
Kidneys
Vitamin D
- hepatocytes secrete a vitamin D precursor
- UV rays turn the precursor into a second precursor
- Second precursor travels to liver and kidneys to be converted into vitamin D
What does vitamin D do in the small intestine?
transfers calcium from food into the blood
Gallbladder
located under the inferior surface of the right lobe of the liver; functions to store and concentrate bile
Biliary tree
connects the liver, gallbladder, and pancreas to the duodenum
Small intestine
main digestio and absorption site for water, proteins, carbohydrates, and lipids; divided into 3 parts
- duodenum
- jejunum
- ileum
Large intestine
1.5 m long connecting to the ileum of the small intestine and terminating at the anus; functions to absorb water and salts and eliminate waste
- peristaltic contractions occur 3-4 times a day to move fecal matter to anus
- 7 parts: ileocecal valve, cecum, appendix, rectum, transverse colon, ascending colon, descending colon, sigmoid colon
What tissue anchors the large intestine (except rectum) to the posterior abdominal wall?
peritoneum
Peritoneum
a serous membrane that lines the walls and contents of the abdomen; connects to stomach, liver, jejunum, and ileum
- reduces friction
- holds in place
- carries vessels
- prevents infection spread
- 2 types: parietal and visceral
Parietal peritoneum
peritoneum that covers the abdominal wall
Visceral peritoneum
covers abdominal organs
Peritoneal cavity
a space between the parietal and visceral peritoneum that contains lubricating fluid
The duodenum lies ___ the peritoneum
behind
Male peritoneum forms a _____ while female peritoneum forms _______
closed sac; an opening for the uterine tubes
carbohydrates, lipids, and proteins are consumed as ____
polymers (that must be broken down to be absorbed)
Chemical digestion
breakdown of polymers into smaller units that can be absorbed by the body
- begins in the mouth, ceases at the large intestine
Where does the majority of chemical digestion occur?
small intestine
Digestion
the breakdown of food into smaller molecules through mechanical and chemical processes
Absorption
the uptake of nutrients from digested food as they move across the intestinal wall into the bloodstream
Carbohydrate digestion
Polysaccharides and disaccharides are broken down into monomeric units
Mouth - salivary amylase
Small intestine - pancreatic amylase, adextrinase
Large intestine - fermentation
Protein digestion
proteins broken down into a single amino acid to enter the blood stream
Stomach - pepsin and gastric juice form peptides
Small intestine - pancreatic juice enzymes (trypsin, chymotrypsin, carboxypeptidase, elastase), brush border enzymes aminopeptidase and dipetidase
Lipid digestion
triglycerides are broken down into monoglycerides and fatty acid
Stomach - lingual lipase (activated in stomach) and gastric lipase (part of gastric juice, breaks down triglycerides in milk)
Small intestine -
The majority of absorption is carried out in the ______
small intestine
Carbohydrate absorption
monosaccharides are transported FROM the brush border of the small intestines THROUGH the cell membranes
- fructose enters via facilitated diffusion
- glucose enters via active transport
Protein absorption
amino acids are absorbed as di- and tri- peptides
they are cotransported with H+ from the intestinal lumen to the surrounding cells to the surrounding cells
The products of lipid digestion are water _____
insoluble
Lipid absorption
lipid products associate with lecithin and bile salts to form micelles
Over 90% of water is absorbed in the _____ , and the rest is absorbed in the _____
small intestine, large intestine
Absorption of water from the lumen of the gastrointestinal tract into the bloodstream occurs through _____ and is dependent on the absorption of ______
osmosis, sodium
a high sodium concentration in the intestinal cells creates a _____
concentration gradient that draws water into cells
Fat-soluble vitamins
Vitamins A, D, E, and K
- transported to brush borders by micelles and absorbed by diffusion
Water-soluble vitamins
B complex and C
- absorbed directly through simple diffusion
Vitamin B12 is absorbed through ______
active transport
Enteric nervous system
a network of nerve cells in the digestive system that controls digestion
- responsible for neural regulation
Enteroendocrine cells
located throughout the mucosa of the stomach and colon
- responsible for hormonal regulation
