Respiratory and Digestive Systems Flashcards
what are the major functions of the respiratory system?
- gas exchange between blood and external environment
- passageways to lungs purify, humidify, and warm incoming air
what is the structure/function of mucosa
respiratory lining
- epithelium resting on a basement membrane
- underlying lamina propria made of areolar CT
How does the respiratory epithelium change down the respiratory tract?
becomes thinner from nose to the alveoli
1. starts as pseudo stratified ciliated columnar
2. changes to simple ciliated columnar
3. to simble cuboidal
4. to simple squamous
what structures are responsible for mucous secretions?
produced from goblet cells of epithelial lining and mucous and serous glands of lamina propria
what is the function of the protein mucin?
increases mucus viscosity and serves to trap dust, pollen, etc.
how much mucous is produced daily?
1-7 tablespoons
what immune defenses are found in mucus?
- lysozyme (antibacterial enzyme)
- defensins (antibacterial proteins)
- immunoglobulin A (antibody)
what is the nasal vestibule?
just inside nares,, sin and particle trapping hairs
where are olfactory receptors located?
in the mucosa on the superior surface
what are conchae and where are they found
projections on the lateral walls of the nasal cavity that increase surface area and air turbulence within the cavity
what separates the nasal cavity from the oral cavity
soft and hard palate
what are paranasal sinuses?
cavities within bones surrounding the nasal cavity
what facial bones have sinuses?
- frontal bone
- sphenoid bone
- ethmoid bone
- maxillary bone
what are the functions of the sinuses?
- lighten the skull
- act as resonance chambers for speech
- produce mucus that drains into the nasal cavity
what is the pharynx?
muscular passage from nasal cavity to larynx
what are the three regions of the pharynx
nasopharynx: superior region behind nasal
oropharynx: middle region behind mouth
laryngopharynx: inferior region attached to larynx
what are the functions of the larynx?
- routes air and food into proper channels
- plays a role in speech
what is the function of the epiglottis?
- protects the superior opening of the larynx
- routes food to the esophagus and air toward the trachea
- when swallowing, the epiglottis rises and forms a lid over opening of larynx
what is the trachea?
- 4 inch long tube that connects larynx with bronchi
- walls are reinforced with shaped hyaline cartilage
- lined with ciliated mucosa
what is the function of the ciliated mucosa that lines the trachea?
- beat continuously in the opposite direction of incoming air
- expel mucus loaded with dust and other debris away from lungs
what are the layers of the tracheal wall?
from inner to outer:
- mucosa: pseudo stratified ciliated columnar
- submucosa: areolar CT with blood vessels, nerves, serous & mucous glands
- tracheal cartilage
- adventitia
what are the primary bronchi?
- formed by division of trachea
- enters the lung at the hilum
how do the right and left primary bronchi differ?
right bronchus is wider, shorter, and straighter than left
how do bronchi divide?
- primary bronchi
- secondary bronchi
- tertiary bronchi
- bronchioles
- terminal bronchioles
what are the structures of the respiratory zone
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
- alveoli
how many alveoli does each lung contain?
300-400 million
what are alveolar pores?
openings providing collateral ventilation
what divide alveoli?
interalveolar septum
what are the layers of the respiratory membrane (air-blood barrier)
- thin squamous epithelial layer lines alveolar walls
- alveolar pores connect neighboring air sacs
- pulmonary capillaries cover external surfaces of alveoli
- on one side of the membrane is air and on the other side is blood flowing past
what are the cell types of the alveolar wall?
- simple squamous alveolar type 1 cells: 95% of alveolar surface area
- alveolar type II cells (septal cells): secrete oily pulmonary surfactant
- alveolar macrophage: leukocytes that engulf microorganisms
By what process does gas cross the respiratory membrane?
diffusion
what role do alveolar macrophages play in gas exchange?
add protection by picking up bacteria, carbon particles, and other debris
what is the function of surfactant in gas exchange?
coats gas exposed alveolar surfaces
where is the apex of the lungs?
superior portion near clavicle
where is the base of the lungs?
inferior portion that rests on the diaphragm
how many lobes does each lung have?
left lung: 2 lobes
right lung: 3 lobes
what are the two types of circulation in the lungs?
pulmonary circulation and bronchial circulation
what is pulmonary circulation?
replenishes oxygen and eliminates CO2
what is bronchial circulation
transports oxygenated blood to tissues of lungs
- bronchial arteries branch off descending aorta
- bronchial veins collect venus blood
what division of the nervous system innervates the respiratory tract?
autonomic nervous system innervates smooth muscles and glands
- sympathetic input from T1-T5 causes bronchodilation
- parasympathetic input from vagus nerve causes bronconstriction
How do the lungs remain inflated?
- interpleural pressure is low
- the chest wall is configured to expand outwards and lungs cling to chest wall due to surface tension of serous fluid
- lungs remain inflated due to intrapulmonary pressure being greater than interpleural pressure
what is respiratory gas transport?
transport of oxygen and carbon dioxide via bloodstream
what is external respiration?
gas exchange between pulmonary blood and alveoli
what is internal respiration?
gas exchange between blood and tissue cells in systemic capillaries
what are the two phases of breathing?
inspiration and expiration
what is occurring during inspiration?
- diaphragm and external intercostal muscles contract
- thoracic cavity expands
- external air is pulled into lungs due to increase in volume and decrease in pressure
what is occurring during expiration?
- as muscles relax, air is pushed out of lungs due to decrease in intra pulmonary volume and increase in pressure
- mostly passive process but can also be forced
how is forced breathing different from quiet breathing?
- requires contraction of additional muscles
- causes greater changes in volume and pressure and moves more air in/out of lungs
what are some examples of nonrespiratory air movements
cough, sneeze, crying, laughing, hiccup, yawn
how much air is moved in a normal breath
about 500 mL (tidal volume)
what factors can influence respiratory capacity?
size, sex, age, physical condition
what is inspiratory reserve volume
the amount of air that can be taken in forcibly over the tidal volume
- usually around 3100 mL
what is expiratory reserve volume?
amount of air that can be forcibly exhaled
- about 1200 mL
what is residual volume?
the air remaining in lungs after expiration
-about 1200 mL
what is vital capacity?
the total amount of exchangeable air
- TV + IRV + ERV
what is anatomic dead space?
the air that remains in conducting zone and never reaches alveoli
- about 150 mL
what is functional volume?
air that reaches the respiratory zone
- about 350 mL
what respiratory sounds can be heard with a stethoscope?
- bronchial sounds: produced by air rushing through large passageways such as trachea and bronchi
- vesicular breathing sounds: soft sounds of air filling alveoli
how is oxygen loaded into the blood in external respiration?
- alveoli always have more oxygen than blood
- oxygen moves by diffusion towards the area of lower concentration
- pulmonary capillary blood gain oxygen
how is carbon dioxide unloaded out of the blood during external respiration?
- blood returning from tissues has higher concentrations of carbon dioxide than air in the alveoli
- pulmonary capillary blood gives up CO2 to be exhaled
what anatomical features of the respiratory membrane contribute to the efficiency of gas exchange?
large surface area and minimal thickness
what is ventilation-perfusion coupling
- ability of bronchioles to regulate airflow and arterioles to regulate blood flow
- ventilation changes by bronchodilation/constriction
- perfusion changes by pulmonary arteriole dilation/constriction
what percent of oxygen in the blood binds to hemoglobin?
98%
how is carbon dioxide transported in the blood?
- most in transported in plasma as HCO3- (70%)
- a small amount is carried inside RBCs on hemoglobin but at different binding sites than oxygen (23%)
- remaining 7% is dissolved in plasma
how is carbon dioxide converted back from its bicarbonate ion form?
- bicarbonate enters RBC
- combine with hydrogen ions to form carbonic acid
- carbonic acid splits to form water and CO2
how does hemoglobin transport oxygen?
- oxygen attached to iron
- carbon dioxide and hydrogen ions bound to globin part
- binding of one substance causes a change in shape of the hemoglobin molecule
how many O2 molecules can each hemoglobin bind?
four O2 molecues
what is the oxygen-hemoglobin saturation curve?
- s shaped non linear relationship that shows that saturation increases as PO2 increases
what is the cooperative binding effect?
each O2 that binds causes a change in hemoglobin making it easier for next oxygen to bind
what is altitude sickness?
adverse physiologic effects from a decrease in alveolar PO2 and low oxygen saturation
how does the presence of 2,3-BPG influence oxygen release from hemoglobin
- binds hemoglobin, causing release of additional oxygen
- certain hormones stimulate erythrocytes to produce this molecule
what is the haldane effect?
- release of oxygen causes a conformational change in hemoglobin that increases amount of CO2 that can bind
what is a right shift?
a decrease in oxygen affinity for hemoglobin that can be caused by increased temperature or an increase in hydrogen ions
what is a left shift?
an increase in oxygen affinity to hemoglobin that can be caused by decreased temperature or a decrease in hydrogen ions
how does internal respiration occur?
- carbon dioxide diffuses out of tissue to blood (loading)
- oxygen diffuses from blood into tissue (unloading)
what are the organs of the GI tract?
- forms a continuous tube
- oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus
What are the accessory digestive organs?
- salivary glands, liver, pancreas
- teeth and tongue
- gallbladder
What are the main functions of the digestive system?
- ingestion
- motility
- secretion
- digestion
- absorption
- elimination
what are the tunics of the GI tract?
from innermost to outermost:
- mucosa
- submucosa
- muscularis
- adventitia
what are the sublayers of the mucosa?
- epithelium: simple columnar allows for secretion/absorption some portions that must withstand abrasion lined by stratified squamous
- lamina propria: composed of aerolar ct, blood vessels, nerves
- muscularis mucosae: smooth muscle deep to lamina propria
what is the submucosa composed of?
areolar and dense irregular CT, blood vessels, lymph vessels, nerves
what is the submucosal nerve plexus?
nerves and gangliea innervating smooth muscle and glands
what are peyer patches?
larger aggregates of lymphatic nodules in distal small intestine
what are the sublayers of the muscularis?
- inner circular layer of smooth muscle
- outer longitudinal layer of smooth muscle
- myenteric nerve plexus: axons and ganglia between layers that control contractions
what is a sphincter?
a thickened muscularis layer that closes off lumen and controls movement of materials into next section of GI tract
How does the muscularis layer mix and propel contents?
mixing: back and forward motion that lacks directional movement and blends ingested materials with secretions
propulsion: directional movement of materials that occurs by peristalsis, the sequential contraction of muscularis
what is the adventitia composed of
areolar CT
What is the enteric nervous system?
sensory and motor neurons within submucosal and myenteric plexus that coordinate mixing and propulsion reflexes
how does the autonomic nervous system affect the digestive system
- parasympathetic innervation promotes GI tract activity
- sympathetic innervation opposes GI tract activity
what do baroreceptors do?
detect stretch in GI tract wall
what is the function of chemoreceptors?
monitor chemical contents in lumen
What is the difference between a short reflex and a long reflex?
short reflexes only involve ENS and coordinates small segments of GI tract while long reflexes involves CNS and coordinates motility, secretions, and accessory organs of GI tract
what is the peritoneum?
serous membrane associated with abdominopelvic cavity
what are intraperitoneal organs?
- organs completely surrounded by visceral peritoneum
- includes stomach, most of s. intestine and part of l. intestine
what are retroperitoneal organs?
- lie directly against posterior abdominal wall and only anterolateral portions covered w/ peritoneum
- includes most of duodenum, pancreas, ascending/descending colon, & rectum
what is the mesentery?
- double layer of peritoneum that supports and suspends intraperitoneal organs
what is the greater omentum?
- covers most abdominal organs and extends inferiorly from inferolateral stomach
- accumulates large amnts of adipose
what is the lesser omentum?
- connects superomedial surface of stomach and proximal end of duodenum to liver
what are the organs and accessory structures of the upper GI tract?
- oral cavity
- salivary glands
- pharynx
- esophagus
- stomach
- duodeum
what are the regions of the oral cavity?
- vestibule: space between gum, lips, cheeks
- oral cavity proper: lies central to teeth and leads posteriorly into oropharynx
what is the function of papillae on the tongue?
projections that are involved in taste
what are the functions of the tongue?
manipulates and mixes materials during chewing, important for swallowing and speech
what type of epithelium lines the oral cavity?
stratified squamous that is mostly nonkeratinized (protects against abrasion)
what are the two types of salivary glands?
- intrinsic salivary glands: unicellular glands within oral cavity that continuously release secretions independent of food, contains lingual lipase
- extrinsic salivary glands: glands outside of oral cavity that produce most saliva (parotid, submandibular, & sublingual)
what is the largest salivary gland?
parotid salivary glands (produce 25-30% of saliva)
- infection of parotid glands causes mumps
what salivary gland produces the most saliva?
submandibular salivary glands
- produce 60-70% of saliva
what are the two secretory cells found within salivary glands?
- mucous cells: secrete mucin, forming mucus upon hydration
- serous cells: secrete watery fluid containing electrolytes and salivary amylase
what is the composition of saliva and how much is secreted per day?
- 99.5% water, salivary amylase, mucin, and other solutes
- 1 to 1.5 liters secreted daily
what are the functions of saliva?
- moistens ingested food to help become bolus
- salivary amylase initiates chemical breakdown of starch
- cleanses oral cavity
how are salivary secretions regulated?
- regulated by salivary nuclei within brainstem
- receptors detect stimuli in oral cavity and send signals to salivary nuclei, signals are received from high brain centers in response to thought of food, increased parasympathetic output to salivary glands
what is mastication?
chewing
- mechanically reduces bulk to facilitate swallowing and increase surface area
- controlled by nuclei in medulla in pons called mastication center
what are the teeth called collectively?
the dentition
what is the structure of a tooth?
- expose crown, constricted neck, with roots that fit tightly into dental alveoli
- bound to processes by periodontal ligament
how many teeth do we have?
- 20 deciduous teeth
- 32 permanent teeth that replace deciduous teeth
what are the types of teeth?
- incisors: most anterior teeth shaped like chisel
- canines: posterolateral to incisors with pointed tip
- premolars: flat crowns with prominent ridges for grinding/crushing
- molars: most posteriorly placed teeth
how many of each type of tooth are in each quadrant
2 incisors, 1 canine, 2 premolars, 3 molars per quadrant
what are gingivae
gums
- composed of dense irregular CT
- overlying nonkeratinized stratified squamous epithelium
what forms the pharynx?
formed by 3 skeletal muscle pairs
- superior, middle, and inferior pharyngeal constrictors
what is the superior esophageal sphincter and where is it?
- contracted ring of circular skeletal muscle at superior end
- area where esophagus and pharynx meet
- closed during inhalation of air
what is the inferior esophageal sphincter and where is it?
- contracted ring of circular skeletal muscle at inferior end
- not strong enough by itself to stop stomach contents from regurgitating
what type of tissue lines the esophagus?
nonkeratinized stratified squamous epithelium
what is the function of the muscularis layer of the esophagus?
2 layers of muscle ensures material moves rapidly out of pharynx
- top 1/3 is skeletal, middle is mixed, bottom 1/3 is smooth
what are the three phases of swallowing?
- voluntary phase
- pharyngeal phase
- esophageal phase
what occurs during the voluntary phase of swallowing?
- occurs after ingestion
- bolus formed as food and saliva mix
- bolus directed towards oropharynx
what occurs during the pharyngeal phase of swallowing?
- involuntary reflex stimulated by tactile receptors around fauces
- signal transmitted to swallowing center of medulla
- as bolus enters oropharynx, elevation of soft palate blocks passageway to nasopharynx
- elevation of larynx by extrinsic muscles move epiglottis
- nerve signals to medulla ensure breath not taken during swallowing
what occurs during the esophageal phase of swallowing?
- involuntary phase when bolus passes through esophagus
- bolus stimulates sequential waves of muscular contraction
- both esophageal sphincters closed at rest and relax when bolus swallowed
what quadrant is the stomach located in?
left upper quadrant
how long do ingested materials spend in stomach?
2-6 hours
true or false, most nutrient absorption occurs in the stomach
false, only small nonpolar substances are absorbed in stomach
what are the four regions of the stomach?
- cardia: entryway from esophagus
- fundus: dome shaped superior region
- body: largest region
- pylorus: funnel shaped pouch
what are the gastric folds of the stomach called and what are their function?
Rugae: allow stomach to expand greatly when filled with food
what type of epithelium lines the stomach?
lined by simple columnar epithelium supported by lamina propria
what are gastric glands?
- extend deep into mucosa from base of each gastric pit
how does the muscularis of the stomach differ from other parts of the GI tract?
it has a third inner oblique layer of muscle
what are surface mucous cells?
- line stomach lumen and extend into gastric pits
- continuously secrete alkaline product containing mucin
- mucous prevent ulceration of stomach lining
what are mucous neck cells?
- deep to base of gasric pit
- produce acidic mucin which maintains acidic conditions
what are parietal cells?
add 2 substances to stomach:
- intrinsic factor: required for absorption of vitamin b12 and production of erythrocytes
- hydrochloric acid: forms from H+ and Cl- secrete across cells surface
what is the function of HCl in the stomach?
- breaks down plant cell walls and animal CT
- denatures proteins
- converts pepsinogen to active pepsin
what are chief cells?
- produce and secrete packets of zymogen granules containing mostly pepsinogen
- also produce gastric lipase which plays a role in fat digestion
what are G cells?
- enteroendocrine cells that are widely distributed in gastric glands
- secrete gastrin hormone which stimulates stomach secretions and motility
What occurs during the process of gastric emptying?
- movement of acidic chyme from stomach into duodenum
- pressure gradient moves contents toward pylorus and increases force against sphincter
- sphincter closes with retropulsion
how are the digestive processes in the stomach regulated?
- pacemaker cells in stomach spontaneously depolarize and establish rhythm of muscle contraction
- force of contraction and gastric gland secretion regulated by nervous reflexes and hormones in 3 phases
what occurs in the cephalic phase?
- cephalic reflex intiated by thought of food
- nerve signals sent to hypothalamus which relays signals to medulla
- vagal stimulation increases in stomach, results in increase in motility and secretions
what occurs in the gastric phase?
- process following bolus reaching stomach
- gastric reflex initiated as baroreceptors detect stomach stretch
- chemo receptors detect protein and increased pH
- results in increase in motility and secretions
what occurs during the intestinal phase?
- processes following chyme reaching small intestine
- involves intestinal reflex which opposes cephalic and gastric reflexes
- causes decrease in stomach motility and secretions
what effect do cholecystokinin and secretin have on stomach?
decrease stomach motility and secretory activity
what are the three regions of the small intestine
duodenum, jejeunum, ileum
where does most chemical digestion and absorption occur?
the small intestine
where is bile produced and stored?
- produced by liver
- stored, concentrated, released by gallbladder
what is the primary function of the large intestine?
- absorbs water, electrolytes, and some vitamins
how long do nutrients typically stay in the small intestine for?
at least 12 hours
what part of the small intestine is the primary region for chemical digestion and nutrient absorption?
the jejunum
what is the largest region of the small intestine?
the ileum (3/5th)
what structure marks the end of the small intestine?
ileocecal valve (sphincter controlling entry to large intestine)
what are circular folds?
- internal folds of mucosal and submucosal tunics of small intestine
- increase surface area for nutrient absorption
- “speed bumps” to slow chyme
- less numerous in ileum
what are villi?
- finger like projections that increase surface area for absorption and secretion
- contain an arteriole, capillary, and venule
- most numerous in jejunum
what are lacteals?
- lymphatic capillary within villus that is responsible for absorbing lipids and lipid soluble vitamins
what are microvilli?
- extensions of plasma membrane of simple columnar cells that increase surface area of small intestine
- form a microscopic brush border with enzymes embedded called brush border enzymes
what are intestinal glands?
- invaginations of mucosa between villi that secrete intestinal juice
what do goblet cells secrete?
- produce mucin, precursor of mucous
- increase in number from duodenum to ileum
what are unicellular gland cells?
synthesize enteropeptidase
what do submucosal glands secrete?
produce alkaline mucus secretion protecting duodenum from chyme
how does smooth muscle aid in motility of small intestine?
- mixes chyme with gland secretions
- moves chyme against new areas of brush border
- propels contents through small intestine by peristalsis
what is segmentation?
- back and forward motion that mixes chyme with gland secretions and intestinal juice
- prevalent early in intestinal phase
what is the migrating motility complex
successive waves of contractions
what is the gastroileal reflex?
ieum contracts and moves contents from ileum to cecum in response to food in stomach
what is the biliary apparatus?
- network of ducts draining left and right lobes of liver
- include left and right hepatic ducts which merge into common hepatic duct
- merges with cystic duct from gallbladder to from common bile duct
what covers the liver?
a CT capsule and layer of visceral peritoneum
how many lobes does the liver have?
4
how does the right lobe of the liver compare to the left lobe?
- right lobe is larger than left lobe
- right lobe contains quadrate and caudate lobes
what is the round ligament of the liver?
remnant of fetal umbilical vein found in inferior free edge of falciform ligament
what is the ligamentum venosum?
the remnant of ductus venosus in embryo
what is the porta hepatis?
- where blood, lymph vessels, bile ducts, nerves, enter and leave the liver
- ex: hepatic portal vein
how does the CT capsule branch throughout the liver?
- forms septa partitioning liver into small hepatic lobules
- structural and functional units of liver contain hepatocytes
what does a portal triad consist of?
hepatic bile ductile, branches of hepatic portal vein and artery
what is the central vein of the liver?
at center if each lobule, drains blood from lobule and pass from portal triads through hepatic sinusoids to central vein
what is the hepatic artery?
- branch of the celiac trunk that carries oxygenated blood to the liver
what is the hepatic portal vein?
- carries deoxygenated and nutrient rich blood from capillary beds of GI tract, spleen, and pancreas
- brings ~75% of blood to liver
- blood mixes as it passes through hepatic lobules
what does bile consist of?
water, bicarbonate ions, bile salts and pigments, cholesterol, lecithin, and mucin
what function do the biles salts and lecithin play in bile?
help mechanically digest lipids
what occurs in cirrhosis of the liver?
hepatocytes replaced by fibrous scar tissue which compresses blood vessels and causes hepatic portal hypertension
what is the most frequent cause of cirrhosis of the liver?
viral infections from hepatitis B or C
what are the tunics of the gallbladder?
from in to out:
- mucosa
- muscalaris
- serosa
what is the endocrine function if the pancreas?
produces and secretes insulin and glucagon
what are the regions of the pancreas?
head: wider portion adjacent to duodenum curve
body: central elongated portion
Tail: tapers towards spleen
what acinar cells and where are they found?
- modified simple cuboidal epithelial cells found in the pancreas
- arranged in saclike acini
- produce and release digestive enzymes
what do the cuboidal duct cells of the pancreas secrete?
alkaline bicarbonate fluid
what is pancreatic juice and how is it formed?
- formed from secretions of acinar cells and pancreatic duct cells
- alkaline fluid that consists of mostly water, HCO3-. and digestive enzymes
what are the digestive enzymes in pancreatic juice?
- pancreatic amylase to digest starch
- pancreatic lipase to digest triglycerides
- inactive proteases that digest proteins when activated
- nucleases for digestion of nucleic acids
What is the function of cholecystokinin (CCK)?
- released from small intestine in response to fatty chyme
- stimulates gallbladder to strongly contract and release bile
- simulates pancreas to release pancreatic juice
- inhibits stomach motility and release of gastric secretions
What is the function of secretin?
- released from small intestine in response to increased chyme acidity
- causes release of alkaline solution containing bicarbonate ion which neutralizes chyme
- inhibits gastric secretions and motility
what is the first portion of the large intestine?
the cecum
- intraperitoneal blind sac in RLQ
- receives chyme from ileum
what is the second portion of the large intestine?
the colon
- forms inverted u shaped arch
- four segments: ascending, transverse, descending, and sigmoid colon
what is the third region of the large intestine?
the rectum
- muscular tube that expands to store feces
- thick transverse folds called rectal valves
what are the two anal sphincters?
internal anal sphincter: involuntary smooth muscle at base of anal canal
external anal sphincter: voluntary skeletal muscle that is normally closed but relaxes during defecation
what are teniae coli?
- thin, longitudinal bundles of smooth muscle that bunch up large intestine into many sacs called haustra
what kind of tissue lines the large intestine?
simple columnar epithelium
- numerous goblet cells
- lacks inteestinal villi
- secrete mucin to lubricate undigested material
what is the indigenous microbiota and what is its function?
- normal bacteria flora in large intestine
- breakdown carbs, proteins, and lipids in chyme
- produce CO2,H+, vit B, Vit K, etc
what makes up feces?
composed of water salts, epithelial cells, bacteria, and undigested material
what is haustral churning?
- relaxed haustrum filling with material
- distension stimulates reflex contractions in muscularis
what are mass movements of the large intestine?
- powerful contractions that involve teniae coli which propel fecal material toward rectum
- occurs 2-3 times a day
what are the main digestion sites of carbs?
oral cavity and small intestine
How are carbs broken down in the oral cavity?
- catalyzed by salivary amylase from salivary glands
- breaks bonds between glucose molecules within starch
- inactivated by low pH of stomach
how are carbs broken down in the small intestine?
- pancreatic amylase secreted as part of pancreatic juice
- continues digestion of starch by further shortening glucose chains
- brush border enzymes such dextrinase, glucoamylase, and maltase finish digestion of starch
How are proteins broken down in the stomach?
- begins with pepsin
- low pH of stomach activates pepsinogen to pepsin and denatures proteins to facilitate chemical breakdown
how are proteins broken in the small intestine?
- enzymes trypsin, chymotrypsin, and precarboxypeptidase relased in inactive form
what are the primary enzymes for lipid breakdown
- lingual lipase: component of saliva activated in stomach
- gastric lipase: produced by chief cells
- pancreatic lipase: released into s. intestine and requires emulsification
