chp 23 exam 4 Flashcards
Mouth is where food is
Associated organs:
Mouth is where food is chewed and mixed with enzyme-containing saliva that begins process of digestion, and swallowing process is initiated
Mouth
Tongue
Salivary glands
Teeth
Mouth (Introduction)
AKA oral (buccal) cavity
- Bounded by lips anteriorly, cheeks laterally, palate superiorly, and tongue inferiorly
- Oral orifice
- -anterior opening
- Walls of mouth lined with stratified squamous epithelium
- -Tough cells that resist abrasion
- -Cells of gums, hard palate, and part of tongue are keratinized for extra protection
- Lips (labia):
- Cheeks
- Oral vestibule
- Oral cavity proper
- Labial frenulum
Lips and cheeks -Lips (labia): orbicularis oris muscle -Cheeks buccinator muscles -Oral vestibule recess internal to lips and cheeks, external to teeth and gums -Oral cavity proper lies within teeth and gums -Labial frenulum median attachment of each lip to gum
Palate
Palate
- Palate forms the roof of the mouth and has two distinct parts
- Hard palate: formed by palatine bones and palatine processes of maxillae with a midline ridge called raphe
- —-Mucosa is slightly corrugated to help create friction against tongue
- Soft palate: fold formed mostly of skeletal muscle
- –Closes off nasopharynx during swallowing
- –Uvula: fingerlike projection that faces downward from free edge of soft palate
Tongue (Introduction)
Intrinsic muscles
Extrinsic muscles
- Tongue occupies floor of mouth
- Composed of interlacing bundles of skeletal muscle
- Functions include:
- -Gripping, repositioning, and mixing of food during chewing
- -Formation of bolus, mixture of food and saliva
- -Initiation of swallowing, speech, and taste
- Intrinsic muscles change shape of tongue
- Extrinsic muscles alter tongue’s position
- Lingual frenulum: attachment to floor of mouth
Tongue (Papillae)
- Filiform papillae:
- Fungiform papillae:
- Vallate (circumvallate) papillae
- Foliate papillae:
Superior surface bears papillae, peglike projections of underlying mucosa
- Filiform papillae: gives tongue roughness to provide friction; only one that does not contain taste buds; gives tongue a whitish appearance
- Fungiform papillae: mushroom shaped, scattered widely over tongue; vascular core causes reddish appearance of tongue
- Vallate (circumvallate) papillae: 8–12 form V-shaped row in back of tongue
- Foliate papillae: located on lateral aspects of posterior tongue
(Terminal Sulcus)
Terminal sulcus: groove located posterior to vallate papillae
- Marks division between:
- -Body: portion of tongue that resides in oral cavity
- -Root: posterior third residing in oropharynx
-Does not contain papillae, but still bumpy because of lingual tonsil, which lies deep to its mucosa
Ankyloglossia
- congenital condition in which children are born with an extremely short lingual frenulum
- Often referred to as “tongue-tied” or “fused tongue”
- Restricted tongue movement distorts speech
- Treatment: surgical snipping of frenulum
Salivary Glands (Introduction) -Functions of saliva Major (extrinsic) salivary glands Minor salivary glands
-Functions of saliva Cleanses mouth Dissolves food chemicals for taste Moistens food; compacts into bolus Begins breakdown of starch with enzyme amylase
Major (extrinsic) salivary glands
- outside of the oral cavity
- produce most of the saliva
Minor salivary glands
- are scattered throughout oral cavity
- make a little saliva
Major salivary glands include:
Parotid:
- anterior to ear and external to masseter muscle
- parotid duct opens into oral vestibule next to second upper molar
Submandibular
- medial to body of mandible
- duct opens at base of lingual frenulum
Sublingual
- anterior to submandibular gland under tongue
- 10–12 ducts into floor of mouth
Two types of secretory cells
- Parotid and submandibular
- Sublingual gland consist
Serous cells:
- -Secretion is mostly water
- -Plus: enzymes, ions, bit of mucin
Mucous cells
-produce mucus
- Parotid and submandibular glands contain mostly serous cells
- Sublingual gland consists mostly of mucous cells
Xerostomia
- dry mouth
- -too little saliva being made
- Remember that normal salivary gland function is vital for oral health
- -Lack of moisture may lead to difficulty with chewing and swallowing
- -Can lead to oral infections
Possible Causes
-medications, diabetes, HIV/AIDS, and Sjögren’s syndrome (autoimmune disease affecting moisture-producing glands throughout body)
Composition of saliva
-Mostly water (97–99.5%)
-Slightly acidic (pH 6.75 to 7.00)
-Electrolytes
Na+, K+, Cl−, PO42−, HCO3−
-Digestive enzymes: salivary amylase and lingual lipase
-Proteins: mucin, lysozyme, and IgA
-Metabolic wastes: urea and uric acid
-Immune functions
—Lysozyme, IgA, defensins, protect against microorganisms
—nitric oxide from nitrates in food also help protect you from microorganisms
Control of salivation
- Major salivary glands activated by
- -Strong sympathetic stimulation
- 1500 ml/day can be produced
- Minor glands continuously keep mouth moist
- Major salivary glands activated by parasympathetic nervous system when:
- -Ingested food stimulates chemoreceptors and mechanoreceptors in mouth
- -Strong sympathetic stimulation inhibits salivation and results in dry mouth (xerostomia)
- –That’s why when you’re nervous your mouth gets dry
- Smell/sight of food or upset GI can act as stimuli
Teeth
Mastication
baby teeth adult teeth
wisdom teeth
Teeth
-Found in gomphoses of the mandible and maxilla
Mastication
process of chewing that tears and grinds food into smaller fragments
Primary (baby teeth)
-20 deciduous teeth, or milk or baby teeth
erupt between 6 and 24months of age
Permanent teeth 32 deep-lying (under baby teeth) -enlarge and develop -roots of baby teeth are resorbed from below --loosen and fall out -Occurs around 6–12years of age -All are in by the end of adolescence
- Wisdom teeth (3rd molars)
- –Third molars may or may not emerge around 17–25 years of age
Clinical – Homeostatic Imbalance (Decay)
- Decaying primary teeth can be painful and may lead to serious infection
- Can cause damage to the permanent teeth
- Primary teeth deserve as much attention as permanent teeth!
- Primary teeth serve as important “place holders” for developing permanent teeth
- Primary teeth can be kept healthy by brushing and limiting exposure to sugary liquids, especially from prolonged bottle feeding.
Teeth are classified according to shape:
Teeth are classified according to shape: -Incisors chisel shaped for cutting -Canines fanglike teeth that tear or pierce -Premolars (bicuspids) broad crowns with rounded cusps used to grind or crush -Molars broad crowns, rounded cusps best grinders During chewing, upper and lower molars lock together, creating tremendous crushing force
Dental formula
Dental formula: shorthand indicator of number and position of teeth
- Shows ratio of upper to lower teeth for only half of mouth; other side is mirror image
- Primary
- permanent
Tooth structure
Tooth structure
Each tooth has two major regions:
-Crown: exposed part above gingiva (gum)
-Covered by enamel, the hardest substance in body
—Heavily mineralized with calcium salts and hydroxyapatite crystals
—Enamel-producing cells degenerate when tooth erupts, so no healing if tooth decays or cracks; needs artificial repair by filling
- Root: portion embedded in jawbone
- -Connected to crown by neck
cement
Periodontal ligament
Gingival sulcus:
Dentin:
Cement: calcified connective tissue
Covers root; attaches it to periodontal ligament
Periodontal ligament
- Forms fibrous joint called gomphosis
- Anchors tooth in bony socket (alveolus)
Gingival sulcus: groove where gingiva borders tooth
Dentin: bonelike material under enamel
Maintained by odontoblasts of pulp cavity
Pulp cavity
pulp
root canal
apical foramen
Pulp cavity: surrounded by dentin
Pulp: connective tissue, blood vessels, and nerves
Root canal: as pulp cavity extends to root
Apical foramen at proximal end of root
Entry for blood vessels, nerves, etc.
impacted tooth
Impacted tooth
-a tooth that remains trapped in the jawbone
-Painful
-Wisdom teeth are most commonly involved.
Treatment: surgical removal
dental carries
dental plaque
-Dental caries (cavities): demineralization of enamel and dentin from bacterial action
- Dental plaque
- -film of sugar, bacteria, and debris
- -adheres to teeth
- Acid from bacteria dissolves calcium salts
- Proteolytic enzymes digest organic matter
- Prevention
- –daily flossing and brushing
gingivitis
Gingivitis
Plaque calcifies to form calculus (tartar)
disrupts seal between gingivae and teeth
Anaerobic bacteria infect gums
Infection is reversible if calculus removed
periodontitis
Periodontitis (periodontal disease)
-Neglected gingivitis can escalate to disease
-Immune cells attack bacterial intruders and own tissues
destroys periodontal ligaments
activates osteoclasts
Cells that dissolve bone so tooth falls out
-May increase heart disease and stroke two ways:
Promotes atherosclerotic plaque formation
Bacteria entering blood can cause clot formation in coronary and cerebral arteries
-Risk factors: smoking, diabetes mellitus, oral piercings and poor oral hygiene
The Pharynx
Food passes from mouth into oropharynx and then into laryngopharynx
Allows passage of food, fluids, and air
Stratified squamous epithelium lining with mucus-producing glands
External muscle layers consists of two skeletal muscle layers
Inner layer of muscles runs longitudinally
Outer pharyngeal constrictors encircle wall of pharynx
The Esophagus
Muscular tube that runs from laryngopharynx to stomach
Is collapsed when not involved in food propulsion
Goes through the diaphragm at esophageal hiatus
Joins stomach at cardial orifice
Gastroesophageal (cardiac) sphincter surrounds cardial orifice
Keeps orifice closed when food is not being swallowed
Mucus cells on both sides of sphincter help protect esophagus from acid reflux
The Esophagus (Structure)
Four tunics
Mucosa
Stratified squamous epithelium
Changes to simple columnar at stomach
Submucosa
Has esophageal glands that secrete mucus to aid in bolus movement
Muscularis externa
skeletal muscle at the beginning (superior)
mixed in skeletal and smooth muscle in the middle
smooth muscle at the end (inferior)
Serosa is replaced by adventitia
heartburn
hiatal hernia
Heartburn
Caused by stomach acid regurgitating into esophagus
First symptom of gastroesophageal reflux disease (GERD)
Causes
excess food/drink, extreme obesity, pregnancy, running
Hiatal hernia
part of stomach protrudes above diaphragm
Can lead to esophagitis, esophageal ulcers, or even esophageal cancer
Deglutition
and two phases:
Reminder
The pharynx and esophagus job is to pass food from mouth to stomach
Deglutition (swallowing)
Requires coordination of 22 muscle groups and two phases:
Buccal phase
voluntary contraction of tongue
Pharyngeal-esophageal phase
involuntary phase that primarily involves vagus nerve
Controlled by swallowing center in medulla and lower pons
stomach
Stomach
temporary storage tank that starts chemical breakdown of proteins
Converts bolus of food to paste-like chyme
Extremely expandable
Empty stomach ~50 ml can expand to 4 L when full
When empty, stomach mucosa forms many folds called rugae
major regions of stomach
Major regions of the stomach
Cardial part (cardia): surrounds cardial orifice
Fundus: dome-shaped region beneath diaphragm
Body: midportion
Pyloric part: wider and more superior portion of pyloric region, antrum, narrows into pyloric canal that terminates in pylorus
Pylorus is continuous with duodenum through pyloric valve (sphincter controlling stomach emptying)
curvatures and mesenteries
Greater curvature: convex lateral surface of stomach
Lesser curvature: concave medial surface of stomach
Mesenteries extend from curvatures and hold the stomach to other digestive organs
Lesser omentum
Runs from lesser curvature to liver
Greater omentum: drapes inferiorly from greater curvature over intestine, spleen, and transverse colon
Blends with mesocolon, mesentery that anchors large intestine to abdominal wall
Contains fat deposits and lymph nodes
Histology of the Stomach
has an extra
Four Tunics
Modified muscularis and mucosa
Muscularis Externa Modifications
Has regular circular and longitudinal smooth muscle layers AND extra third layer, the oblique (diagonal) layer
allows stomach to churn, mix, and move chyme
Also allows pummeling motion
increases physical breakdown and forces chyme into small intestine
Mucosa Modifications
Simple columnar epithelium entirely composed of mucous cells
Secrete two-layer coat of alkaline mucus
Surface layer traps a bicarbonate-rich fluid layer beneath it
Gastric pits
lead into gastric glands
gastric glands make gastric juice
Glandular Cells of the Stomach (Mucous Neck Cells)
types of gland cells
mucous neck cells
Types of gland cells
Glands in fundus and body produce most gastric juice
Mucous neck cells, Parietal cells, Chief cells, Enteroendocrine cells
Mucous neck cells
Secrete thin, acidic mucus of unknown function
parietal cells
Parietal cells
Secretions include:
Hydrochloric acid (HCl)
pH 1.5–3.5; denatures protein, activates pepsin, breaks down plant cell walls, and kills many bacteria
Intrinsic factor
Glycoprotein required for absorption of vitamin B12 in small intestine
secrets HCL and intrinsic factor
chief cells
Chief cells Secretions include: Pepsinogen: inactive enzyme that is activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) Lipases Digests ~15% of lipids
secrets Pepsinogen lipase
enteroendocrine cells
Enteroendocrine cells
Secrete chemical messengers into lamina propria
Act as paracrines
Serotonin and histamine
Hormones
Somatostatin (also acts as paracrine) and gastrin
secretes hormones and paracrine
mucosal barrier
Mucosal barrier protects stomach thick layer of bicarbonate-rich mucus tight junctions between epithelial cells prevent juice seeping underneath tissue damaged epithelial cells are quickly replaced surface cells replaced every 3–6 days
gastritis
ulcers
Gastritis
Inflammation caused by anything that breaches stomach’s mucosal barrier
Peptic or gastric ulcers
Can cause erosions in stomach wall
If erosions perforate wall, can lead to peritonitis and hemorrhage
Most ulcers caused by bacterium Helicobacter pylori
Can also be caused by non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin
reminder of what the stomach does
Denatures proteins by
Pepsin carries out enzymatic digestion
Reminder of what the stomach does: Carries out breakdown of food Serves as holding area for food Delivers chyme to small intestine Denatures proteins by HCl Pepsin carries out enzymatic digestion of proteins Milk protein (casein) is broken down by rennin in infants Results in curdy substance
Protein Digestion in the Stomach
-Milk protein (casein
broken down by
-Denatures proteins by HCl
-Pepsin
Enzyme that digests of proteins
-Milk protein (casein
broken down by rennin in infants
Makes “curds”
Alcohol, Aspirin and Intrinsic Factor
Alcohol and aspirin
absorbed into blood through the mucosa
both are lipid soluble
Intrinsic factor
Synthesis and secretion is the only stomach function essential to life
Required vitamin B12 absorption
Reminder:
B12 needed for red blood cells to mature
Lack of intrinsic factor causes pernicious anemia
Treated with B12 injections
Regulation of Gastric Secretion (Introduction)
neural and hormonal
Gastrin
stimulates
Gastric mucosa secretes >3 L of gastric juice/day
Regulated by:
Neural mechanisms
Parasympathetic (Vagus nerve) stimulation increases secretion
Sympathetic stimulation decreases secretion
Hormonal mechanisms
Gastrin
stimulates HCl secretion by the stomach
Stimulates gastrin antagonist hormones by the small intestine
gastric secretions are broken down into three phases
Gastric secretions are broken down into three phases
Cephalic (reflex) phase
Gastric phase
Intestinal phase
cephalic phase
Cephalic (reflex) phase
Conditioned reflex triggered by aroma, taste, sight, thought
Varies based on life experience!
