A&P II Chapter 23: Digestive System (EXAM 4)
permanent dentition
"adult teeth"
ankyloglossia how is it corrected?
"tongue-tied", a very short lingual frenulum that restricts the tongue movements and distorts speech corrected by surgically snipping the frenulum.
what are the three layers of the mucosa
(1) lining epithelium, (2) lamina propria and (3) muscularis mucosae
the steps involved in swallowing
(study)
what muscle forms the lips? what muscle forms the cheeks?
- lips: orbicularis oris - cheeks: buccinators
what does the external muscle layer of the pharynx contain? how is the inner layer arranged?
-2 skeletal muscle layers -the inner layer cells run longitudinally
in halitosis, what is the oder caused by? what smells?
-accumulation of anaerobic protein-digesting bacteria at the back of the tongue -the metabolic activity of these bacteria produces hydrogen sulfide (rotten egg smell), methyl mercaptan (also in feces), cadaverine (rotting corpse smell) and others
2. smooth muscle and glands are the effectors of digestive activity (acts in response to stimuli) - how to they act in response?
-act to initiate reflexes that promote lumen content mixing and movement of the contents along the GI tract by smooth muscle in the GI tract walls -and can also promote or inhibit glands that secrete digestive juices into the GI tract lumen or hormones into the blood
accessory digestive organs which organs are included?
-aid in digestion, but food does not actually pass through most of these -includes the teeth, tongue, gallbladder, salivary glands, liver and pancreas
1. ingestion where does this take place?
-bringing food into the digestive tract (eating) -only in the mouth
hepatic portal circulation
-collects the now nutrient-rich venous blood that drains from the digestive tract and delivers it to the liver (NOT vena cava so very unique to this system) -liver will pull our nutrients to store and redirect then dump into hepatic veins and then vena cava
what are three things the greater omentum contains?
-contains many fat deposits, making it look like a lacy apron -it also has large collections of lymph nodes -the immune cells in these lymph nodes police the peritoneal cavity and organs
2. submucosa what does it contain?
-external to the mucosa, areolar connective tissue -contains blood and lymphatic vessels, lymphoid follicles and nerve fibers that supply the surrounding tissues of the GI tract wall -also contains many elastic fibers that can help the stomach regain its normal shape after temporarily storing a big meal
in the gastrointestinal tracts what is said about the food that travels through? how long?
-food inside this tube is technically outside of the body since the tube is open to the external environment at both ends -it is 30 ft long in a cadaver and 22 ft in a living person because of muscle tone
where are the two major intrinsic nerve plexuses found? what do these two nerve plexuses contain and do?
-found in the walls of the alimentary canal -enteric neurons that provide the major nerve supply to the GI tract wall and regulate GI motility. They intertwine throughout the digestive tract to regulate activity
where do the sympathetic fibers run from? what supplies the parasympathetic fibers?
-from the thoracic splanchnic nerves relay through the celiac plexus. -parasympathetic fibers are supplied by the vagus nerve
3. mechanical breakdown what mechanisms does this include?
-increases the surface area of the food to prepare it for enzyme digestion -includes chewing, mixing food with saliva by the tongue, churning food in the stomach, and segmentation
1. mucosa functions
-moist epithelial membrane that lines the alimentary canal -secrete mucus, digestive enzymes and hormones; absorb the end products of digestion into the blood and protect against infectious disease
2. propulsion
-moving food through the alimentary canal
alimentary canal organs (gastrointestinal tract (GI)) structure? function?
-organs that the food physically travels through -continuous muscular tube that winds through the body from the mouth to the anus -it digests food (breaks it down into smaller pieces) and absorbs the fragments through its lining into the blood
filiform papillae functions what gives the tongue a whitish appearance?
-roughen the tongue surface to aid in licking semisolid foods (icecream) and provide friction to manipulate food -smallest and most numerous papillae and contain keratin to stiffen them (this gives the tongue a whitish appearance)
3. muscularis externa what does it contain and form?
-surrounds the submucosa, responsible for segmentation and peristalsis -contains and inner circular layer and outer longitudinal layer. -the circular layer thickens at several locations to form sphincters- valve to control food passage between organs and prevent backflow
what is the enteric nervous system? how many neurons?
-the GI tract's very own nerve system -consists of over 100 million neurons (more than the entire spinal cord!)
what is the function of the enteric nervous system?
-these enteric neurons COMMUNICATE with one another to regulate digestive activities -information is sent to intestines to warn them food is coming, so slows down speed of food to stomach
what are the accessory digestive glands known for?
-they produce many different secretions that help breakdown food -release digestive enzymes in GI tract to aid in food breakdown
impacted tooth which teeth are common to this?
-tooth that is trapped in the jawbone, causes pressure and pain and must be removed surgically -wisdom teeth commonly become impacted
which of the digestive process activities is the mouth and it's accessory organs involved in?
1. ingestion 2. mechanical breakdown 3. propulsion 4. digestion
the digestive system processes food with which 6 activities?
1. ingestion 2. propulsion 3. mechanical breakdown 4. digestion 5. absorption 6. defecation
3 key concepts to regulation of digestive activity
1. many different mechanical and chemical stimuli provoke digestive activity 2. smooth muscle and glands are the effectors of digestive activity (acts in response to stimuli) 3. hormones and neurons control digestive activity
size of the stomach how long volume when empty and when full
15-25 cm (6-10 inches) long volume of 50 ml and diameter of about the large intestine when empty, volume of 4 L (1 gallon) and can extend almost to the pelvis when really distended
how much saliva on average gets secreted a day
1500 ml/day (1.5L)
dental formula of primary dentition
2𝐼, 1𝐶, 2𝑀 (𝑢𝑝𝑝𝑒𝑟 𝑗𝑎𝑤) ------------------------- x2 (20 teeth) 2𝐼, 1𝐶, 2𝑀 (𝑙𝑜𝑤𝑒𝑟𝑗𝑎𝑤)
dental formula of permanent dentition
2𝐼,1𝐶,2 𝑃𝑀, 3𝑀 (𝑢𝑝𝑝𝑒𝑟 𝑗𝑎𝑤) ------------------------------ x2 (32 teeth) 2𝐼,1𝐶,2𝑃𝑀, 3𝑀 (𝑙𝑜𝑤𝑒𝑟𝑗𝑎𝑤)
vallate papillae
8-12 of these large papillae form a V-shaped row near the back of the tongue. They look like fungiform papillae with an added groove around them
how much of water does saliva contain?
97-99.5% water so it is hypoosmotic and slightly acidic (pH 6.75-7.00)
what are most ulcers in the stomach caused by?
Helicobacter pylori- an acid resistant strain of bacteria that burrow like drill bits through the mucus and destroy the mucosal barrier. Half of the population has this bacteria, but it only causes problems in 10-20% of those individuals
how does saliva protect against microorganisms?
IgA antibodies, lysozyme (enzyme that inhibits bacterial growth and defensins (local antibiotic and cytokine to call in defensive cells)
mesentery
a double layer of peritoneum that connects the digestive organs to the body wall to anchor them in place, provide routes for blood vessels, lymphatics and nerves to reach the digestive viscera and stores fat
what is the intrinsic factor that parietal cells secrete?
a glycoprotein necessary for vitamin B12 absorption in the small intestine
saliva contains mucin
a glycoprotein that dissolves in water to form a thick mucus that lubricates the oral cavity and hydrates food
what can also cause heartburn and how?
a hiatal hernia - the superior part of the stomach protrudes above the diaphragm due to a structural abnormality. Gastric juices enter the esophagus because the diaphragm no longer reinforces the sphincter
what septum does the tongue contain?
a median septum of connective tissue and each half of the tongue contains identical muscle groups
the stomach
a temporary storage tank that begins the process of protein digestion and converts food into a paste called chyme
what does the mucosal barrier of the stomach have a thick coat of to protect the stomach?
a thick coat of bicarbonate mucus that builds up on the stomach wall
what are chemoreceptors in the mouth strongly activated by?
acidic foods
peristalsis (major means of propulsion)
alternating waves of contraction and relaxation of muscle in the walls of the alimentary canal that squeezes food along and mixes it
oral orifice what does it extend to?
anterior opening of the oral cavity. Posteriorly the mouth is continuous with the oropharynx
what are mechanoreceptors activated by?
any mechanical stimulus in the mouth (sight, smell or thought of food can be enough to increase saliva secretion)
oral vestibule
area between the teeth/gums and the lips/cheeks
oral cavity proper
area inside the teeth/gums
what occur as the adult teeth develop?
as these "adult" teeth develop, the roots of the milk teeth are resorbed and the teeth fall out
apical foramen
at the end of each root canal, allows the pulp structures to enter the pulp cavity
extrinsic skeletal muscle fibers
attach to the tongue from points of origin on bone and alter the tongues position (protruding, retracting, moving from side to side, etc)
lingual frenulum
attaches the tongue to the floor of the mouth and limits how far back it can move
ventral mesentery
attaches to the anterior wall
greater omentum
attaches to the greater curvature of the stomach and covers the coils of the small intestine and wraps the spleen and transverse large intestine
dorsal mesentery
attaches to the posterior abdominal wall. This is the case in most places.
halitosis
bad breath
where are the accessory digestive organs in the body in relation to the GI tract?
besides the teeth and tongue (which are in the oral cavity/mouth), the rest of the organs or glands lie outside of the GI tract and connect to it by ducts
peritoneal cavity
between the 2 peritoneums, a space that contains slippery serous fluid from the serous membrane that allows the mobile organs to glide across each other and the body wall
arterial supply of GI
branches of the celiac artery serve the spleen, liver and stomach
mesenteric supply
branches of the mesenteric arteries that serve the small and large intestines, receives 1⁄4 of the cardiac output (more than this after a large meal)
4. digestion
breakdown of food molecules to their chemical building blocks by enzymes that are secreted into the alimentary canal
premolars/bicuspids
broad crown with a rounded tip, used for grinding and crushing
tongue
bundles of skeletal muscle fibers, makes up the floor of the mouth
heartburn what symptoms emerge? what is it? first symptom of what?
burning, radiating substernal pain when stomach acid regurgitates into the esophagus, first symptom of gastroesophageal reflux disease (GERD)
the most common cause of peritonitis
burst appendix that sprays feces containing bacteria all over the peritoneum
how does the stomach protect itself being exposed to very harsh conditions (corrosively acidic gastric juice and protein-digesting enzymes capable of digesting the stomach itself)?
by producing the mucosal barrier which is created by 3 factors
calculus/tarter what do the hard deposits dp? what is early infection called? how is this reversible?
calcification of dental plaque that accumulates on the gums. The hard deposits deepen the sulcus creating a risk for infection from anaerobic bacteria. Early infection is gingivitis which involves red, sore, swollen and bleeding gums. Reversible if the calculus is removed.
cement what does it attach the tooth to?
calcified connective tissue that covers the root and attaches the tooth to the periodontal ligament which anchors the tooth in the bony socket
how are long reflexes initiated?
can be initiated by signals inside or outside of the GI tract. This allows extrinsic controls to influence digestive activity
1. ingestion
can only occur at the mouth
how many roots does each kind of tooth have? incisors, canines, premolars, upper molars, lower molars, third molar?
canines, incisors and premolars usually have 1 root, the first two upper molars have 3 roots, the lower molars have 2 roots and the third molar has 1 fused root, but varies
lamina propria
capillaries nourish the epithelium and absorb digested nutrients. It also contains isolated lymphoid follicles that are part of the mucosa-associated lymphoid tissues (MALT) that help protect against bacteria and pathogens (supporting layer)
dental cavities caused by what? the bacteria produce what that dissolve the calcium salts? what digests the rest?
caused by enamel and dentin demineralization by bacteria. The decay begins when dental plaque (film of sugar, bacteria and debris) adheres to the teeth. The bacteria metabolize the sugar producing acids that dissolve the calcium salts. Enzymes digest the rest
what occurs with saliva when food is ingested?
chemoreceptors in the mouth send signals to the salivatory nuclei in the brainstem which increases parasympathetic nervous system activity. Impulses are then sent via motor fibers in the facial (VII) and glossopharyngeal (IX) nerves that increase secretion of watery saliva (from serous cells)
where does mechanical breakdown take place?
chewing (mouth), churning (stomach), segmentation (small intestine)
2. mechanical breakdown by the mouth
chewing of food/mastication
mumps
childhood disease, inflammation of the parotid glands caused by myxovirus that spreads from person to person by saliva
incisors
chisel-shaped, used to cut or nip off pieces of food
what does secretion of saliva function for?
clean the mouth and kill bacteria, dissolve food chemicals to be tasted, moisten food and help form it into a bolus and begins the digestion of starchy foods with the enzyme amylase
neck (tooth)
connects the crown and root
pyloric part
consists of the pyloric antrum, pyloric canal and terminates at the pylorus which is continuous with the duodenum through the pyloric sphincter
what does activation of the sympathetic division cause in relation to saliva?
constricts blood vessels to the salivary glands and inhibits saliva release
pulp cavity
contains blood vessels, connective tissue and nerve fibers (all collectively called "pulp")
what does the pharyngeal wall mucosa contain?
contains friction-resistant stratified squamous epithelium supplied with mucous producing cells (similar to oral cavity)
muscularis externa
contains the typical longitudinal and circular muscle layers (for mixing, churning, and moving food along) and also has an incomplete inner oblique smooth muscle layer (for pummeling and physically breaking down food and forcing it into the small intestine by jackknifing the stomach into a V- shape)
in short reflexes, control of segmentation and peristalsis patterns is voluntary or autonomic? what cells are involved?
control of segmentation and peristalsis patterns is automatic and involves pacemaker cells and reflex arcs between enteric neurons in the same or different organs
what do acid producing bacteria near the gums and stomach do?
convert nitrates in saliva to nitric oxide which is also bactericidal
visceral peritoneum
covers the external surface of most of the digestive organs (balloon around hand)
chief cells
cuboidal, mostly in the basal regions, produce pepsinogen (inactive form of pepsin)
what does shedding of damaged mucosal epithelial cells do for the mucosal barrier of the stomach?
damaged cells are rapidly replaced by division of undifferentiated stem cells that reside at the gastric pit-gastric gland junction. The surface mucosal epithelial cells of the stomach (exposed the most to the harsh conditions) are turned over/renewed every 3-6 days while the more sheltered and deep cells within the gastric glands have a much longer life span
why can't enamel heal?
decayed/cracked areas of enamel cannot heal because the cells that produce enamel degenerate when the tooth erupts
primary dentition
deciduous/baby/milk teeth
enteroendocrine cells
deep in gastric glands, release chemicals into the interstitial fluid of the lamina propria such as histamine and serotonin (act locally as paracrines), somatostatin (local paracrine and diffuses into blood) and gastrin (hormone, plays a role in regulation of stomach secretion and motility)
propulsion in the pharynx and esophagus is accomplished by what?
deglutition/swallowing and peristalsis
why does dehydration also inhibit salivation?
dehydration also inhibits salivation because low blood volume reduces filtration pressure in capillary beds
terminal sulcus what does this separate
directly behind the vallate papillae, this groove separates the part of the tongue in the oral cavity (its body) from its portion in the oropharynx (its root)
causes of heartburn
eating or drinking in excess and obesity, pregnancy and running which all push or slosh abdominal contents upwards
what solutes does saliva contain?
electrolytes (Na+, K+, Cl-, PO43-, HCO3-), digestive enzymes (salivary amylase, lingual lipase), proteins (mucin, lysozyme, IgA) and metabolic wastes (urea and uric acid)
6. defecation
elimination of indigestible substances (formed into feces) via the anus
crown
enamel covered exposed part of the tooth above the gum/gingiva
how does enamel differ from dentin and cement?
enamel differs from dentin and cement because it doesn't have collagen and is almost entirely mineral
which tooth structures are all calcified and are similar to bone? how do they differ from bone?
enamel, dentin and cement they are avascular (no blood vessels)
what can frequent and prolonged heartburn cause?
esophagitis (inflammation of the esophagus) and esophageal ulcers
canines/eyeteeth
fang-like, used to tear and pierce
4. adventitia (INSTEAD OF SEROSA)
fibrous, connective tissue.
how does food reach the esophagus and why?
food in the laryngopharynx is automatically routed into the esophagus because the epiglottis closes off the larynx
pharynx (movement of food)
food moves from the mouth to the oropharynx and then the laryngopharynx (both are passageways for food, fluids and air)
hard palate formed by what? why the hard surface? why is the surface ribbed?
formed by the palatine bones and the palatine processes of the maxillae. It forms a hard surface that the tongue can push food against when chewing. The mucosa on the sides of the raphe (midline ridge) is ribbed to create friction
what does the palate of the mouth form?
forms the roof of the mouth and contains the soft and hard palate
where is lamina propria found?
found in the pharynx (the tonsils) and in the appendix
what is resistant of H. pylori in the stomach? what test can diagnose it and what is the treatment?
gastric mucin is antibacterial and protective against H. pylori. A breath test can detect the bacteria which is treated by a course of antibiotics
what happens if the mucosal barrier of the stomach is breeched?
gastritis (inflammation of the stomach wall) occurs
functions of the tongue
grips food and repositions it between the teeth during chewing, mixes food with saliva forming it into a compact mass called a bolus, initiates swallowing by pushing the bolus into the pharynx and helps form consonants (k, d, t, etc.) when we speak
does the root of the tongue have papillae? explain
has no papillae, but is still bumpy because the lingual tonsil just under its mucosa is nodular
what do retroperitoneal organs have?
have an adventitia on the side facing the dorsal body wall and a serosa on the side facing the peritoneal cavity
what is a clinical problem of the esophagus
heartburn
periodontal disease/periodontitis what does this cause? common?
if the calculus is not removed, infection forms, the periodontal ligament is destroyed and the bone dissolves. Most common cause of adult tooth loss
dentin tubules what do they contain?
in the dentin, contain odontoblasts- the cells that secrete and maintain dentin
mucous neck cells
in the neck and basal regions, produce a thin, soluble, acidic mucus (very different from surface epithelium mucous cell secretion)
minor/intrinsic salivary glands
in the oral cavity mucosa, augment (increase) salivary output
intrinsic skeletal muscle fibers where and allow what?
in the tongue and not attached to bone, allow the tongue to change shape (thicker, thinner, longer, shorter), but not position as needed for speech or swallowing
peritonitis causes?
inflammation of the peritoneum piercing abdominal wound, perforating ulcer that leaks stomach juices into the peritoneal cavity or poor sterile technique during abdominal surgery
3. propulsion by the mouth
initiated in the mouth by swallowing (the mouth participates only in the first phase of swallowing)
where to the teeth sit?
inside sockets in gum-covered sections of the mandible and maxilla
pharyngeal- esophageal phase voluntary or involuntary? controlled by what? what transmits the motor impulses from the swallowing center to the muscles in the pharynx and esophagus? what is blocked off when food enters the pharynx?
involuntary, controlled by the swallowing center in the brainstem cranial nerves (especially the vagus nerves) transmit the motor impulses from the swallowing center to the muscles in the pharynx and esophagus. When food enters the pharynx, the trachea is blocked off and respiration is inhibited
what two things are necessary for propulsion to take place?
involves swallowing (voluntarily initiated) and peristalsis (involuntary)
irritation to what can also cause an increase in salivation?
irritation of the lower GI tract can also increase salivation to help wash away the irritants
where is the esophagus and what does it contain
it is in the thoracic cavity and does NOT have a serosa, but has adventitia
how long does it take for food and fluid to be swallowed?
it takes solid food about 8 seconds to travel from the oropharynx to the stomach and it takes fluids about 1-2 seconds (fluids are helped by gravity)
in the mucosal barrier of the stomach what prevent gastric juices from leaking into the tissues?
joining of the mucosal epithelial cells by tight junctions preventing gastric juices from leaking into the underlying tissues
what do the lips and cheeks do and what muscle are they made of?
keep food between the teeth when chewing and are made of skeletal muscle (voluntary) covered with skin
major/extrinsic salivary glands location and function
lie outside of the oral cavity and empty their secretions into it and these produce most saliva
some treatments of heartburn
lifestyle and dietary changes, antacids and prescription drugs
what are the walls of the mouth lined with? what do the gums, hard palate, and back of the tongue contain?
lined with thick stratified squamous epithelium and the gums, hard palate and back of the tongue are slightly keratinized (protein lining) for protection from food
parieteal peritoneum
lines the body wall, continuous with the visceral peritoneum
what else do chief cells secrete?
lipases (fat-digesting enzymes) that account for 15% of GI tract lipolysis
in a few cases, ulcers are not caused by H. pylori, but what?
long term NSAID use
what are the first teeth that appear around 6 months of age?
lower central incisors
short reflexes
mediated entirely by enteric nervous system plexuses in response to stimuli within (INTRINSIC) the GI tract
when do minor and major salivary glands release saliva
minor salivary glands keep the mouth moist major salivary glands get activated and secrete in large amounts by incoming food
soft palate mobile or immobile? what does it do when swallowing? what is it attached to? what projects of the soft palate?
mobile and formed of skeletal muscle that rises to close off the nasopharynx when swallowing (why you can't breathe and swallow at the same time). The soft palate is attached to the tongue by the palatoglossal arches and to the wall of the oropharynx by the palatopharyngeal arches (more posterior). The uvula is a finger-like projection off the free edge of the soft palate.
what are the four layers of the esophagus?
mucosa, submucosa, muscularis externa, and adventitia
the 4 wall layers of the alimentary canal
mucosa, submucosa, muscularis externa, serosa
what surrounds the gastroesophageal or cardiac sphincter and why?
mucous cells around the sphincter to protect the esophagus from stomach acid
gland cell types of the stomach mucosa
mucous neck cells, parietal cells, chief cells, and enteroendocrine cells
cells of the gastric pits vary by region pyloric antrum?
mucus and hormone (gastrin) producing cells
cells of the gastric pits vary by region cardia and pylorus?
mucus secreting cells
2. submucosa of esophagus
mucus secreting esophageal glands, when a bolus moves through, these glands compress and secrete mucus to grease the walls and aid in food passage
mumps in adult males can cause what?
mumps in adult males carries a risk (25%) of infecting the testes and leading to sterility
esophagus
muscular tube about 10 inches long, collapsed when not involved in food propulsion
fungiform papillae shape? color?
mushroom shaped, widely scattered over the tongue surface and contains a vascular core that gives it a reddish tone
1. mucosa of esophagus
nonkeratinized stratified squamous epithelium, changes to simple columnar in the stomach (for secretion)
is the submucosa layer or serosa of the stomach modified?
nope
does absorption occur at the mouth?
not typically except a few drugs that can be absorbed through the oral mucosa (ex: nitroglycerine for chest pain relief).
intraperitoneal/peritoneal organs
organs that kept their mesentery and remain in the peritoneal cavity
retroperitoneal organs
organs that lost their mesentery during development and sit behind the peritoneum (most of the pancreas and duodenum and part of the large intestine
where does propulsion take place?
oropharynx (swallowing) esophagus, stomach, small and large intestines (peristalsis)
4. serosa
outermost layer, visceral peritoneum in intraperitoneal organs and made up of aeroler connective tissue
what is the symptoms of mumps?
pain with chewing or opening the mouth, fever, pain when swallowing acidic foods
parotid gland location and connection
paired, triangular, major salivary glands, in front of the ear between the masseter muscle and the skin. The parotid duct connects it to the oral cavity and opens into it next to the second upper molar. Branches of the facial nerve run through the parotid gland
when do all milk teeth come in?
pairs of teeth continue to erupt every 1-2 months until 24 months old when all 20 milk teeth have come in
what does parasympathetic and sympathetic input do to digestive activity?
parasympathetic input enhances digestive activity while sympathetic inhibits it
root (tooth)
part of the tooth embedded in the jawbone
what fatal disease can periodontal disease lead to?
periodontal disease can lead to heart disease and stroke because the inflammation promotes atherosclerotic plaque and the bacteria entering the blood from the gums promote clot formation
what process does food passage through the esophagus involve?
peristalsis
what can gastritis lead to? damage of the tissues, which results in what?
permanent damage to the underlying tissue can cause peptic/gastric ulcers (erosion of the stomach wall). Gastric ulcers cause extreme pain and can cause perforation of the stomach wall leading to peritonitis (inflammation of the peritoneum) and massive hemorrhage
folliate papillae
pleat-like and on the sides of the back of the tongue
4. digestion what part of this occurs at the mouth
polysaccharide digestion begins in the mouth
what are the 2 sets of teeth that form by the age of 21?
primary dentition and permanent dentition
serous cells composition of mucous which glands contain these cells?
produce a watery secretion containing enzymes, ions and a little mucin the parotid and submandibular glands contain mostly serous cells
mucous cells composition of mucous which glands contain these cells?
produce mucus, a stringy, viscous solution the sublingual glands contain mostly mucous cells buccal glands (intrinsic) contain equal numbers of both
dentin what does it act as?
protein-rich bonelike material under the enamel cap, forms the bulk of the tooth and acts as a shock absorber during biting and chewing
what does pulp do for the teeth
pulp supplies nutrients to the tissues of the tooth and provides tooth sensation
1. many different mechanical and chemical stimuli provoke digestive activity - what do these receptors respond to?
receptors in the wall of the GI tract organs respond to stretch of the organ by food in its lumen, changes in osmolarity/solute concentration and pH and the presence of end products of digestion
treatment of peritonitis
removal of infectious debris and megadoses of antibiotics
parietal cells secrete HCl making the stomach very acidic (pH 1.5-3.5), what is this necessary for?
required for prime activity of pepsin (protein digesting enzyme) and kills bacteria
segmentation (mechanism of mechanical breakdown)
rhythmic local constrictions of the small intestine that mixes food with digestive juices and repeatedly moves different parts of the food over the intestinal wall to enhance absorption efficiency (contractions of the muscle but does not move food forward (squeezes it))
lesser omentum
runs from the liver to the lesser curvature of the stomach where it becomes continuous with the visceral peritoneum that covers the stomach
molars
same as premolars, but have 4-5 cusps and are the best at grinding. The upper and lower molars lock together during chewing to produce a strong crushing force
parietal cells
secrete HCl and intrinsic factor, have 3 prongs with dense microvilli (fuzzy pitchforks) which provides large surface area for secretion
the salivary glands contain what 2 types of secretory cells?
serous cells and mucous cells
peritoneum
serous membrane (smooth/slippery) that lines the abdominopelvic cavity (where most digestive organs reside) and covers the abdominal organs
epithelium
simple columnar (except the mouth, esophagus and anus which is stratified squamous) with many mucus secreting cells. The mucus prevents the digestive organs from being digested by the enzymes working within them and eases food passage (thick mucous prevents trauma)
modification of the layers of the stomach mucosa
simple columnar epithelium made entirely of mucous cells that produce a double layer coat of alkaline mucus
3. muscularis externa of esophagus
skeletal muscle in the top, a mix of skeletal and smooth muscle in the middle and all smooth muscle in the inferior third
muscularis mucosae
small layer of smooth muscle that allows for movement of the mucosa which can enhance absorption and secretion
sublingual gland
small, almond-shaped, in front of the submandibular gland under the tongue, opens via 10-20 ducts into the oral cavity floor
blood supply of the gastrointestinal tract happen through what circulation?
splanchnic circulation- arteries that branch off the abdominal aorta and serve the digestive organs and the hepatic portal circulation
the cardia (name because near the heart)
surrounds the cardial orifice through which food enters the stomach from the esophagus
how many muscles does swallowing involve and through what two phases?
swallowing involves the coordination of 22 muscles through the buccal phase and pharyngeal- esophageal phase
the main role of the digestive system
take in food, break it down into nutrient molecules, absorb those molecules into the bloodstream to build and fuel the body's cells then rid the body of the indigestible remains
function of the teeth
tear/grind food to physically break it down to smaller pieces
which system serves the stomach?
the autonomic nervous system
4 regions of the stomach
the cardia, fundus, body, and pyloric part
long reflexes
the enteric nervous system sends information to the CNS (via visceral afferents) and receives sympathetic and parasympathetic branches of the autonomic system that synapse with neurons in the intrinsic plexuses of the intestinal wall
where does the esophagus reach? where does it pierce the diaphragm?
the esophagus goes straight into the mediastinum of the thorax piercing the diaphragm at the esophageal hiatus to enter the abdomen
from chief cells, how does pepsinogen activated?
the first pepsinogen released is activated by HCl from parietal cells in the apical region, but once pepsin is present, it can also catalyze the conversion of pepsinogen to pepsin
which papillae contain taste buds?
the fungiform, vallate and foliate papillae contain taste buds
what surrounds the cardial orifice and why?
the gastroesophageal or cardiac sphincter to close off the orifice when food is not being swallowed
gingival sulcus
the groove where the gingiva touches the tooth
enamel
the hardest substance in the body, mineralized with calcium salts, directly bears the force of chewing, as thick as a dime
what does the mucous layer lining contain?
the lining has millions of deep gastric pits that lead into gastric glands that produce gastric juice
what are the boundaries of the oral cavity/mouth?
the lips, cheeks, palate and tongue
labial frenulum
the middle fold that connects the inside of each lip to the gums
the body of the stomach
the midportion, continuous with the funnel-shaped
the alimentary canal organs include what?
the mouth, pharynx, esophagus, stomach and small (duodenum, jejunum, ileum) and large intestines (transverse colon, descending colon, ascending colon, cecum, sigmoid colon, rectum, appendix and anal canal)
5. absorption
the movement of the digested end products, vitamins, minerals and water from the GI tract lumen through the mucosal cells by active or passive transport and into the blood or lymph
how does the stomach appear when empty?
the mucosa and submucosa are thrown into folds called rugae
3. hormones and neurons control digestive activity - how does the nervous system control digestive activity?
the nervous system controls digestive activity via instrinsic controls (short reflexes) and extrinsic controls (long reflexes)
mesenteries aka
the omenta, anchor the stomach to other digestive organs and the body wall.
contraction of what muscles propel food into the esophagus?
the outer layer (pharyngeal constrictor muscles) encircle the wall like 3 stacked fists and contract to propel food into the esophagus
which division of the autonomic nervous system controls the release of serous (watery) saliva?
the parasympathetic division
how does the body keep peritonitis localized?
the peritoneal coverings stick together around the infection site to localize the infection and give macrophages time to prevent the inflammation from spreading, but if spread it becomes lethal
which of the digestive process activities is the pharynx and esophagus involved in?
the pharynx and esophagus act as channels to transfer food from the mouth to the stomach and as such, their only digestive function is propulsion
root canal
the pulp cavity in the root
submandibular gland
the size of a walnut, sits along the medial aspect of the body of the mandible. Its duct runs under the mucosa of the oral cavity floor, opening at the lingual frenulum base
3. hormones and neurons control digestive activity - where do hormones get secreted from and where to they go and how do they act?
the stomach and small intestine also have hormone-producing cells that when stimulated, release their hormones into the interstitial fluid of the extracellular space. The blood and interstitial fluid distribute the hormones to their target cells where they affect secretion or contraction
the fundus
the stomach's dome-shaped top, tucked under the diaphragm and bulges superolaterally to the cardia
which arteries provide blood supply to the teeth?
the superior and inferior alveolar arteries (branches of the maxillary artery) provide the blood supply to the teeth
what nerves serve the teeth?
the superior and inferior alveolar nerves (branches of the trigeminal nerve) serve the teeth
what does the surface mucous layer of the mucosa contain?
the surface mucus layer contains thick, insoluble mucus that traps bicarbonate rich fluid under it
which division of the autonomic nervous system controls release of mucin?
the sympathetic division (in particular fibers from T1-T3) controls the release of thick, mucin-rich saliva (from mucous cells)
when do wisdom teeth emerge?
the third molars (wisdom teeth) emerge between age 17-25
how many teeth in a full set of permanent teeth?
there are 32 teeth in a full set of permanent teeth
mastication is this process voluntary or reflexive?
this process is partly voluntary (putting the food in our mouth and closing the jaw) and partly reflexive (the pattern and rhythm of jaw movements are controlled by stretch reflexes and in response to pressure input from receptors in the cheeks, gums and tongue). The reflexive part can be taken over under voluntary control when desired
in the stomach, where is the arterial blood supply through? what do the corresponding veins drain into?
through the gastric and splenic branches of the celiac trunk and the corresponding veins drain into the hepatic portal vein
anything that inhibits saliva secretion promotes what?
tooth decay, which makes talking and eating difficult
location of the stomach
upper left quadrant of the peritoneal cavity, hidden by the liver and diaphragm
the buccal phase voluntary or involuntary? occurs where? when does this phase end? what receptors get stimulated? what is initiated?
voluntary, occurs in the mouth this phase ends when a food bolus or saliva leaves the mouth stimulating the tactile receptors in the back of the pharynx to initiate the next phase
what are some of the things that saliva contains?
water, solutes, mucin, antibodies, and enzymes
cells of the gastric pits vary by region body and fundus?
where most digestion occurs, the glands are much larger and produce most stomach secretion
cardial orifice
where the esophagus enters the stomach
the two major intrinsic nerve plexus and their location
• Submucosal nerve plexus- in the submucosa • Myenteric nerve plexus- between the circular and longitudinal muscle layers of the muscularis externa
