Digestive System Flashcards
What lines the oral cavity?
Oral mucosa
What are the three types of oral mucosa?
- Musculatory mucosa
- Lining mucosa
- Specialized mucosa
Where is musculatory mucosa found?
Gingiva and hard palate
Surface epithelium of musculatory mucosa?
Keratinized or parakeritinized stratified squamous epithelium
Lamina propria of musculatory mucosa?
- Papillary layer - think, loose CT (has blood vessels, nerves, sensory receptors, and some Meissner’s corpuscles)
- Reticular layer - more dense CT
Where is the lining mucosa found?
Soft palate, underside of tongue, floor of mouth, cheeks, and lips
Surface epithelium of lining mucosa?
Nonkeratinized stratified squamous epithelium (thicker than keratinized areas)
Vermilion border and lips = keratinized stratified squamous epithelium
Lamina propria of lining mucosa?
loose CT lined with blood vessels and nerves
Submucosa of lining mucosa?
more dense CT
Where is specialized mucosa found?
Dorsal surface of tongue
Surface epithelium of specialized mucosa?
- Keratinized stratified squamous epithelium on FILIFORM PAPILLAE
- Stratified squamous epithelium on all other papillae
General function of specialized mucosa?
Move food and TASTE
Tongue mucosa location?
thicker dorsally; thinner and smoother posteriorly
Surface epithelium of tongue mucosa?
- includes PAPILLAE (fungiform, filiform, foliate, vallate)
- Small salivary (von Ebner) glands associated with VALLATE PAPILLAE (produce serous fluid to cleanse taste buds)
- taste buds located on all papillae EXCEPT filiform
Lamina propria of tongue mucosa?
loose CT; adipose possible
Submucosa of tongue mucosa?
contains lingual salivary glands
Intrinsic tongue muscles
NO external attachment!!! 4 alternating muscles - change shape of tongue for phonation and movement of food 1) superior longitudinal m 2) vertical m 3) transverse m 4) inferior longitudinal m
Layers of teeth listed outside to inside
- ameloblasts
- enamel
- dentin
- predentin
- odontoblast
- dental papilla
Ameloblasts
- polarized COLUMNAR cells
- LOSE following tooth eruption
- Produce ENAMEL
Enamel
- hardest substance in body
- cannot make more after tooth eruption
Dentin
- harder than bone
- contain thin dentinal tubules containing nerves and cell processes of ODONTOBLASTS
Predentin
-precursor to dentin before mineralization
Odontoblast
- columnar cells lining pulp cavity
- survive in adults
- repair and produce DENTIN (maintain)
Dental Papilla
- aka, dental pulp
- CT with many blood vessels and nerves
- potential problem = excessive inflammation
Types of salivary glands?
- Parotid gland
- Submandibular gland
- Sublingual gland
Parotid gland total salivay output?
~30%, but largest salivary gland
Parotid gland facts
- most affected by mumps
- facial nerve passes through it
- 100% serous producing
- becomes infiltrated with adipose as one ages
Products produced by parotid gland?
- salivary amylase (alpha-amylase) - breaks down carbs
- Lysosome
- Secretory IgA
Submandibular gland total salivary output?
~60%
Submandibular gland facts
- fatty infiltration by midlife possible
- produces mucous AND serous products (~80-90% serous)
- has serous DEMILUNES
Sublingual gland total salivary output?
~5%, smallest
Sublingual gland facts
- mucous AND serous production (~80% mucus)
- all serous from serous demilunes (no separate serous acini)
Functions of saliva
- lubricating and cleansing oral cavity
- Antibacterial
- Dissolve food materials for taste sensation
- Initiate digestion (amylase, lipase)
- Aid swallowing
- wound healing (clotting factors, epidermal growth factor)
Parasympathetic effect of saliva secretions
Increase amount of WATERY secretion
Sympathetic effect of saliva secretions
Decrease amount of saliva with THICKER consistency (dryer oral cavity)
Mucosa (general terminology)
- surface epithelium
- lamina propria
- muscularis mucosae: SMOOTH muscle
Submucosa (general terminology)
- more dense CT
- LARGER blood vessels
- submucosal (Meissner) plexus
Muscularis externa (general terminology)
- Myenteric (Auerbach) plexus (found btwn circular and longitudinal m layers; influences musc. externa)
- Typically smooth muscle
- Normal fiber orientation = inner circular, outer longitudinal
Serosa/Adventitia
Serosa - edge of simple squamous epithelium; serous producing
Adventitia - CT; seen with vertical organs
Function of esophagus
Transfer bolus to stomach from oropharynx
Mucosa - surface epithelium of esophagus
Stratified squamous
Contains LANGERHANS CELLS - an APC with some phagocytosis possible
Mucosa - lamina propria of esophagus
- loose areolar CT*
- Can have esophageal cardiac glands - produce NEUTRAL mucus to protect epithelium
- Location = near pharynx (1st inch) and near stomach (last inch)
Mucosa - muscularis mucosae of esophagus
- discontinuous layer of LONGITUDINAL muscle
- THINNER distally (by pharynx) and THICKER proximally (by stomach)
Submucosa of esophagus
contains ESOPHAGEAL GLANDS - produce slightly acidic mucus to lubricate movement of food
Muscularis externa of esophagus
Normal fiber pattern (inner circular, outer long.)
- Upper 1/3 = all SKELETAL
- Middle 1/3 = smooth and skeletal
- Lower 1/3 = all SMOOTH
Adventitia/serosa of esophagus
Primarily ADVENTITIA except last 1-2 inches are serosa (after diaphragm)
Esophageal associated sphincters (2 physiological)
1) Pharyngoesophageal Sphincter - between oropharynx and esophagus
2) Gastroesophageal Sphincter - between esophagus and stomach (prone to problems; abrupt to change)
Characteristics for physiological sphincters
- NO THICKENING of circular muscle in muscularis externa
- Pressure gradient aids movement (muscle contraction and gravity)
Function of the stomach
- continue to digest CARBS
- primary storage of food
- SOME nutrient breakdown (primarily chemical)
Mucosa - surface epithelium of stomach
- simple columnar*
- CELLS = Surface mucosa and Regenerative cells
Surface Mucosa Cells (stomach)
= surface lining
- produce thick, visible mucus
- secrete BICARBONATE IONS (buffering)
Regenerative Cells (stomach)
Bases of pits
Mucosa - lamina propria of stomach
loose, vascular CT present in small amounts between glands
Mucosa - muscularis mucosae of stomach
smooth muscle layer (often 3 layers - well developed)
1) inner longitudinal
2) outer longitudinal
3) outermost circular/oblique
Submucosa of stomach
- HIGHLY vascular
- *location of AVA - function to shut down activity and secretion fast
- Submucosal (Meissner’s) plexus - to influence MUCOSA
Muscularis externa of stomach
- 3 muscle layers possible (especially btwn CARDIAC REGION and GREATER CURVATURE)
1) innermost oblique
2) middle circular (well developed)
3) outer longitudinal (thin) - normal pattern in other areas (inner circ, outer long)
- Myenteric (Auerbach’s) plexus - stimulate muscularis externa
Serosa of stomach
ALL serosa. no adventitia
Three regions of the stomach
1) Cardiac region
2) Gastric region
3) Pyloric region
Cardiac region of stomach
-shorter PITS - lead to cardiac glands with a coiled base
- cells =
Surface mucus (primarily)
Neck mucus
DNES and parietal cells (few)
*NO chief cells!
-smallest region; obtains much mucus
Gastric region of stomach
aka, zymogenic gland GASTRIC GLANDS 3 regions 1) Isthmus 2) Neck 3) Base
ISTHMUS of gastric glands
Cells
1) Surface mucus
2) DNES cells
Surface mucus cells (gastric glands; isthmus)
- live 3-5 days
- produce THICK, visible mucus that traps bicarbonate ions (alkaline)
- Function = protect mucosa from auto-digestion and the rougher components of chyme
DNES cells
-enteroendocrine cells Types: 1) Type D 2) Type EC 3) Type G
Type D; DNES cells (stomach)
- produces SOMATOSTATIN
- inhibits release of hormones by nearby DNES cells and HCL release
- *DECREASES gastric acid
Type EC; DNES cells (stomach)
- produces SEROTONIN and SUBSTANCE P
- increases gut motility
Type G; DNES cells (stomach)
- produces GASTRIN
- stimulates:
1) HCL and pepsinogen secretion
2) gastric motility
3) regenerative cells in body of stomach - coffee, alcohol, AA’s all stimulate type G
NECK of gastric glands
Cells:
1) Neck mucus cells
2) Regenerative cells - replace all cell types
3) Parietal (oxyntic) cells
4) DNES cells
Neck mucus cells
- live ~6 days
- produce a soluble, less alkaline mucus (slightly acidic)
- Function = to lubricate gastric contents
Parietal (oxyntic) cells
- live ~150-200 days
- secretes or produces acid
- add columnar cells with intracellular canaliculi
- produce:
1) very strong HCl; made at 0.8 pH and buffered immediately to 1-2 pH
2) *Gastric intrinsic factor - enzyme; necessary for vit. B12 absorption
Chronic Gastritis
- can lead to PERNICIOUS ANEMIA
- low number of PARIETAL cells can lead to low amounts of INTRINSIC FACTOR
- will decrease vit. B12 absorption which is necessary for RBC maturation
- stomach lining irritation –> INFLAMMATION
BASE of gastric glands
Cells:
1) Chief (zymogenic) cells
2) Parietal cells
3) DNES cells (few)
Chief (zymogenic) cells
- live ~60-90 days
- produce:
1) Pepsinogen (primarily) - to break down proteins
2) Gastric Lipase (some)
Pyloric Region of stomach
- deeper pits, very twisted and branched pyloric glands (shorter glands)
- Cells:
1) Surface mucus, DNES, parietal (primarily)
2) Neck mucus that can produce some lysosome (some)
Pyloric Sphincter
-ANATOMICAL sphincter between the pylorus of the stomach and the duodenum
Characteristic of an anatomical sphincter
- well developed inner circular layer or muscle in the ME
- inner circular layer in ME can be independently controlled
General function of Small Intestine
- digestion
- absorb nutrients
- produce intestinal hormones (using DNES cells)
Surface adaptations of Small Intestine
- PLICA CIRCULARES (valves of Kerckring) - permanent folds of mucosa and submucosa; found throughout duodenum, jejunum, and proximal ileum
- VILLI
- MICROVILLI - on luminal cell surface
Mucosa - surface epithelium of small intestine
- simple columnar
- Cells:
1) Enterocytes
2) Goblet cells
3) DNES cells (~11 types in SI)
4) Regenerative cells (crypts)
5) Paneth cells
6) M (microfold) cells
Enterocytes
aka, surface absorptive cells: contain MICROVILLI
- Functions
1) absorb water and nutrients
2) terminal digestion in GLYCOCALYX; cells produce the enzymes and absord the monosaccharides and peptides created
Goblet Cells
Fewest in duodenum and most in ILEUM
DNES cells (SI)
~11 types in SI
1) Type I
2) Type K
3) Type S
DNES; Type I (SI)
- produces CCK
- CCK stimulates
1) gallbladder contraction
2) pancreatic secretion of enzymes from SEROUS ACINI
DNES; Type K (SI)
- produces GIP
- Inhibits HCl release
DNES; Type S (SI)
- produces SECRETIN
- *stimulates pancreas secretion of bicarbonate from the pancreatic ducts
- inhibits HCl release and movement of chyme into SI
Paneth cells
- long lived (~20 days)
- location = base of CRYPTS (intestinal glands)
- function = produce LYSOZYME
M (microfold) cells
- location = ileum over PEYER’S PATCHES
- contain large intracellular pockets that are fairly open to the LP; sample foreign antigens in gut lumen and transfer antigens to lymphocytes and dendritic cells that have entered the M cell pockets
- function = promote HUMORAL IMMUNITY
- Important in maintaining GUT FLORA
Mucosa - lamina propria of SI
- loose areolar CT*
- found in VILLUS CORE
- **LACTEALS - lymphocyte capillaries (lipid absorption)
- smaller blood vessels
- some longitudinal smooth m
- borders intestinal glands (=crypts of Lieberkuhn)
Mucosa - muscularis mucosae of SI
thin but present, connects to smooth muscle in villi
Submucosa of SI
- dense fibroelastic CT
- VERY vascular; larger blood vessels
Submucosa of SI (duodenum)
- Duodenal (Brunner) glands - seromucus glands
- products produced:
1) Alkaline mucus; to neutralize chyme
2) Urogastrone; inhibits HCl secretion and increase mitosis of epithelial cells
Submucosa of SI (Jejunum)
NO structures of significance
Submucosa of SI (Ileum)
- location of PEYER’S PATCHES - groups of regularly occuring large lymph nodules
- Submucosal (Meissner’s) plexus - PARASYMP. innervation; influences mucosa
Muscularis externa of SI
- normal pattern (inner circ, outer long)
- Myenteric (Auerbach) plexus - stimulates ME for peristalsis
Serosa/Adventitia of SI`
Serosa - all of JEJUNUM and ILEUM; first and last 1-2 cms duodenum
Adventitia - vertical (descending) portion of DUODENUM
**only one with BOTH serosa and adventitia!!
Ileocecal Valve
- found btwn ileum and cecum of colon
- a physiological AND anatomical sphincter
Appendix
aka, vermiform appendix
-a blind pouch, on the right, extending from the CECUM
Mucosa of appendix
SE - simple columnar with surface absorptive cells, goblets, regenerative, and DNES
LP - yes
MM - poorly developed
- short crypts,
- NO VILLI
- no to infrequent Paneth cells
Submucosa of appendix
- thick layer with large blood vessels
- numerous lymph nodules
Muscularis externa of appendix
Normal pattern, but thin
Also, just serosa
Function of appendix
- humoral immunity
- reservoir for good bacteria
General functions of the colon
- primary = absorption of water
- compaction, lubrication, and elimination of feces
- production of some vitamins
Mucosa of colon
SE - simple columnar with many GOBLET cells and surface absorptive cells, some regenerative and few DNES cells
LP - typical and has intestinal glands (crypts)
MM - normal
-lacks: VILLI and PANETH CELLS
Submucosa of colon
typical
Muscularis Externa of colon
- *NOT NORMAL PATTERN
- Outer longitudinal m is gathered into bands called TENIAE COLI and is discontinuous
- constant tonus of teniae coli results in sacculations called HAUSTRA
Serosa/Adventitia of colon
Serosa - transverse and sigmoid colon
Adventitia - ascending and descending colon
General function of rectum
store fecal material
Surface epithelium of rectum
- simple columnar*
- similar to colon EXCEPT
1) Transverse rectal folds (luminal wall folds)
2) NO teniae coli in ME; more complete long. m’s
3) *luminal wall covering includes ADVENTITIA
Surface epithelium of anal canal
-transitions to stratified squamous
Glands of anal canal
- ANAL GLANDS extend into SM and produce mucus to lubricate lumen
- CIRCUMANAL GLANDS (apocrine glands) in skin surrounding anus
Mucosa and submucosa of anal canal
- contain LONGITUDINAL FOLDS creating anal columns
* NO muscularis mucosae in anal canal
Internal anal sphincter
a think circular layer of smooth m within the muscularis externa
-stay CONTRACTED until triggered to relax; NOT anatomical
External anal sphincter
a STRIATED (voluntary) muscle from the pelvic floor
Luminal wall covering of anal canal
ADVENTITIA (just like the rectum)
Peptic Ulcer Disease
2 causes:
1) Insufficient protection from HCL and PEPSIN - damaged mucus coat, too much HCL and pepsin
2) Helicobacter pylori
-if luminal acidity is decreased, damaged tissues can repair in 1-2 months
Gastroesophageal (esophageal) reflux
- cause = stomach chyme backing up into the lower esophagus (common)
- contributing factors = chronic gastritis, hiatal hernia, pregnancy, incompetent lower esophageal sphincter, subluxations
Barrett’s Esophagus
- precancerous condition
- stratified squamous epithelium is replaced by MUCUS-SECRETING SIMPLE COLUMNAR EPITHELIUM in lower esophagus (metaplasia)
Parasympathetic Stimulation in general
From VAGUS NERVE
- EXCEPT decending colon and rectum from SACRAL N’s
- STIMULATE peristalsis
- INHIBIT sphincters
- ACTIVATES secretion
Sympathetic Stimulation in general
from SPLANCHNIC NERVES
- INHIBITS peristalsis
- CONTRACTS sphincters
- control blood flow to gut
