Lecture 2 - Histology 1 (Baekey) Flashcards Preview

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what are the 3 different layers of lips within the oral cavity?

1. mucosa
2. submucosa
3. core


what cell type is found within the mucosa of the lips?

stratified squamous epithelium (keratinized in herbivores not carnivores)


what type of tissue do you find within the core layer of the lips?

fibroelastic connective tissue and skeletal muscle


what does the primary palate form from?

caudal growth of the medial palatal process


what does the secondary palate form from?

lateral palatal processes that elevate and grow medially and use in the center with the primary palate and nasal septum


in what species do you most commonly see a cleft palate? what is it caused by?

brachycephalic dogs, Abyssinian cats

can be caused by ingestion of lupine (wildflowers) by pregnant sheep or cattle


what layers do you see within the hard palate

1. mucosa - keratinized stratified squamous epithelium
2. lamina propria - extensive vascular beds for heat exchange


what is the function of the soft palate?

divides oropharynx and nasopharynx


what is on the dorsal and ventral surface of the soft palate?

dorsal surface: nasopharynx w/ respiratory epithelium
ventral (oral) surface: keratinized stratified squamous epithelium


what are the layers of the soft palate?

1. lamina propria
2. core: fibrous connective tissue and skeletal muscle


what cell types do you find in the tongue?

stratified squamous epithelium covering a core of skeletal muscle


what are the 5 different tyeps of papillae?

1. filiform
2. conical
3. fungiform
4. foliate
5. vallate (circumvallate)


what characteristics about filiform papillae are significant?

its keratinized (especially in cats) and in rows


what characteristics about conical papillae are significant?

keratinized; located on dorsal surface of root


what characteristics about fungiform papillae are significant?

gustatory (taste buds), scattered


what characteristics about foliate papillae are significant?

taste buds, serous glands at base


what characteristics about vallate (circumvallate) papillae are significant?

ringed by furrow; taste buds; serous glands at base


what cell types do you find in taste buds?

gustatory cells
sustentacular cells
basal cells
nerve fibers


location of tastes

sweet = tip of tongue
salt = tip
sour (acid) = sides
bitter = region of circumvallate papillae


taste is mediated by what cranial nerves?

7, 9, and 10


describe the development of teeth

1. invagination of oral ectoderm forms dental lamina
2. dental buds form at base of dental lamina
3. dental buds differentiate into inverted cups called enamel organs, which produce deciduous teeth


what is dental papilla derived from?
and what does it form?

dental papilla is derived from neural crest

forms from tooth dentin and pulp


define eruption

occurs in each deciduous tooth as downward growth of root exerts pressure against alveolar bone, and the crown is forced upward to break through enamel organ and gingiva


describe the development of permanent teeth

a second bud forms off of the dental lamina. the growing permanent tooth puts pressure on the root of the deciduous tooth, causing the root to be resorbed and the deciduous tooth to fall out


what is an example of ectopic teeth?

ear teeth in horses


what are the 3 cell types seen in teeth

1. ameloblasts
2. odontoblasts
3. cementoblasts


describe ameloblasts

apical processes (Tome's processes) secrete slightly mineralized rods; mineralization initiates in rods, forming enamel (the hardest substance in the body)


describe odontoblasts

neural crest origin
- deposit predentin at the dentinoenamel junction
- predentin is mineralized, forming dentin
- odontoblastic processes extend as odontoblasts retreat


describe cementoblasts

forms cementum which binds dentin to alveolar bone via peridontal ligaments


what are the two types of teeth?

1. brachydont
2. hypsodont


what are the four parts of a brachydont tooth?

1. crown
2. neck
3. root
4. pulp cavity


what is significant about the crown of a brachydont?

enamel covers dentin
ameloblasts disintegrate at eruption


what is significant about the neck of a brachydont?

attachment to gum epithelium is weak, providing entry point for infection


what is significant about the root of a brachydont?

cementum covers dentin
anchored to bone by fibrous bundles called periodontal ligaments


what is significant about the pulp cavity of a branchydont?

contains loose connective tissue, blood vessels, nerves


what animals have a hypsdont teeth

all horse teeth, ruminant cheek teeth, rodent incisors, pig canines


what are significant characteristics of a hypsdont teeth?

constantly erupting and growing

enamel organ breaks open before tooth erupts, cementum is then deposited on enamel and ameloblasts continue to make enamel

infundibulum provides additional enamel surface for chewing


what are the major salivary glands?

parotid, mandibular, sublingual, molar (cat), zygomatic (carnivores)


what is significant about adenomeres in salivary glands?

they are predominately serous


what is significant about myoepithelial cells in salivary glands?

they contract to express secretions


what cell types do you find within ducts of salivary glands

low cuboidal epithelum to stratified squamous epithelium


what is significant about striated ducts in salivary glands?

columnar epithelium
striations are due to mitochondria and infoldings of basal membrane; these influence ionic and water content of saliva


what tunics lie within the esophagus?

1. mucosa - has 3 laminar sublayers
2. submucosa - has mixed glands and a submucosal nerve plexus
3. muscularis - inner circular, outer longitudinal and has a myenteric nerve plexus


what are the 3 layers within the mucosa of the esophagus?

1. lamina epithelialis - stratified squamous
2. lamina propria - contains many lymph nodes
3. lamina muscularis - increases in thickness caudally, exhibits longitudinal folds


what is the cell type of the muscularis tunic of the esophagus in various species?

dogs, ruminants = striated
pigs, horses, cats, humans - striated cranially, smooth caudally
birds - all smooth


where is the myenteric nerve plexus located within the muscularis tunic within the esophagus?

between the circular and longitudinal muscle layers


where are submucosal and myenteric plexuses found?

throughout the gut tube and constitute the enteric nervous system, derived from neural crest


what is the function of myenteric plexus?

gut motility


function of submucosal plexus

sensing the environment within the lumen, regulating gastrointestinal blood and lymph flow and controlling epithelial cell function


interstitial cells of Cajal

myoid cells of mesenchymal origin that are also found in these plexuses. they provide a pacemaker function to the peristaltic action of the enteric nervous system


how is healing in the esophagus?

poor; due to leakage, poor tissue strength and connective tissue support and segemented/marginal blood supply


what are the tunics of the glandular stomach

mucosa: gastric folds, gastric pits
lamina propria: carnivores have stratum compactum and submucosal and myenteric nerve plexuses


name the 4 regions of the glandular stomach

1. esophageal = stratified squamous epithelium
2. cardiac = simple columnar, branched, coiled glands
3. fundic = simple columnar, longer tubular glands w/o branching
4. pyloric = similar to cardiac but with deeper gastric pits


where is the pyloric spincter located?

in tunica muscularis at gastroduodenal junction


mucosal lining cells

simple columnar surface epithelium expands and contracts depending upon degree of distension caused by fodo itnatek. these cells secrete a neutral mucus that lubricates and protects the stomach lining. the apical portion of these cells exhibits short microvilli.


what are the 4 epithelial cells of gastric glands

1. parietal cells - secretes HCl
2. mucous neck cells - located between the parietal cells; secrete acid mucous
3. chief (zymogen) cells - secrete gastric enzymes (pepsin)
4. enteroendocrine cells - secrete monoamine and peptide hormones into lamina propria and blood. upon stomach distension G cells secrete gastrin, which stimulates HCl release by parietal cells.


what is repair and replacement of the stomach like?

repair is excellent

gastric lining cells are replaced every 2 - 3 days
glandular cells are replaced every 5 - 7 days


name the parts of the compound forestomach

1. rumen
2. reticulum
3. omasum
4. abomasum


significance of reticulum

function: fermentation
- concial papillae (no smooth muscle)
core of tunica muscularis


significance of rumen

function: mechanical breakdown
has core of isolated smooth muscle made of laminal muscularis mucosa
- has secondary and tertiary papillae


significance of omasum

function: mechanical breakdown
- primary folds contain lamina muscularis
- secondary papillae present


significance of abomasum

same as glandular stomach
- major chamber used at birth


what are some adaptations to increase absorptive and secretory surface

1. increased length
2. circular mucosal folds
3. glands
4. villi
5. microvilli


what are the regions of the small intestine (3)

1. duodenum: main site of submucosal glands
2. jejunum
3. ileum: peyer's patches are large lymph nodule aggregations


what are the 3 tunics located in the small intestine?

1. mucosa
2. submucosa
3. muscularis


what are the layers within the mucosa of the small intestine

1. lamina epithelium
2. lamina propria
3. lamina mucularis


what is located within the lamina propria located within the mucosa of the small intestine

- crypts of Lieberkuhn (mucosal glands)
- capillary network and lymph lacteals in villi
- stratum compactum in carnivore


what is significant about the lamina muscularis located within the mucosa of the small intestine

extends into villi and serves to pump lacteals and capillaries


what is contained within the submucosa of the small intestine

- submucosal glands in the duodenum secrete an alkaline fluid that neutralizes stomach acids
- submucosal nerve plexuses innervate the villi


what is located within the muscularis of the small intestine

inner circular and outer longitudinal layers
- myenteric nerve plexus


what type of cells are found in both nerve plexuses (submucosal and myeneteric nerve plexus)

interstitial cells of Cajal - they are modified myoid cells of mesenchymal origin that interact with nerve terminals and serve as pacemakers for the contractile activity of the gut muscles


what is another name for submucosal nerve plexuses?

Meissner's nerve plexus


what is another name for myenteric nerve plexuses?

Auerback's nerve plexus


what cell types do you find wtihin the surface mucosa of the small intestine?

1. lining cells (enterocytes)
2. goblet cells
3. enteroendocrine cells
4. lymphocytes


what is the function of lining cells aka enterocytes? what do they look like?

terminal digestion of carbs and proteins and absorption

- they are columnar with apical microvilli densely packed into a brush border


what is the function of goblet cells

in surface mucosa they = secrete protective mucus
in intenstinal crypts of Lieberkuhn they - produce a glycoprotein mucus that lubricates and protects the surface of the epithelium


what do enteroendocrine cells secrete?

locally-acting hormones such as serotonin, glucagon, secretin, cholecystokinin


what do lymphocytes do within the surface mucosa of the small intestine?

migrate thru epithelium; more numerous caudally


what cell types do you find within the intestinal crpts of Lieberkuhn (straight tubular glands) within the small intestine

1. lining cells
2. goblet cells
3. enteroendocrine cells
4. paneth cells
5. basal stem cells


function of paneth cells

secrete enzymes; regulate microbial environment through secreted products


function of basal stem cells

retain mitotic activity and replace other cells


what is repair and replacement of the small intestine like?

good; stem cells in crypts replace other cells approx every 3 days


what are the functions of the large intestine

1. microbial activity; including fermentation in nonruminant herbivores
2. absorption of water, vitamins and electrolytes
3. secretion of lubricating mucus


histological features of large intestine

1. larger lumen than small intestine
2. villi not prominent
3. longitudinal folds instead of plicae circulares
4. diffuse and nodular lymphatic tissue
5. submucosal and myenteric nerve plexus


4 regions of the large intestine

1. cecum
2. colon
3. rectum
4. anus


features of cecum

have longitudinal folds called taeniae ceci (in pigs and horses)


features of colon

contain taeniae coli (pigs and horses)
- have longitudinal bands of smooth muscle
- have crypts of Lieberkuhn


features of rectum

thicker tunica muscularis than colon
- tunica adventitia present


features of anus

columnar epithelium of rectum gives way to stratified squamous eptihelium of anus
- glands are prominent on anal side of recto-anal junction.
- at ano-cutaneous junction epithelium becomes keratinized in some species


repair and replacement of large intestine

replacement similar to small intestine
- repair is less successful because of foreign material, bacteria and inadequate blood supply, leakage is common


what are the functions of hepatocytes

1. synthesize sugars, plasma proteins, clotting factors, lipids, urea, etc.
2. secrete bile salts, bile acids
3. excrete bile pigments
4. store lipids, vitamines, glycogen
5. transofrm toxins, drugs, hormones
6. metabolize lipids, proteins, carbs
7. hematopoesis occurs during fetal development


hepatic lobule

plates of parenchyma delimited by interlobular connective tissue
- sinusoids
- has central vein in center



- sandwiched between plates
- fenestrated
- hae no basal lamina
- endothelium is surrounded by hepatocyte microvilli


biliary system of flow is:

1. bile canaliculi
2. biliary ductules
3. interlobular bile duct
4. intrahepatic duct
5. hepatic duct


what is the flow from the hepatic duct to the gall bladder?

hepatic duct --> cystic duct --> gall bladder


what is the flow from the hepatic duct tot he duodenum?

hepatic duct --> bile duct --> duodenum


what makes of the portal triad in interlobular connective tissue?

1. interlobular bile duct
2. hepatic artery
3. hepatic portal vein


what makes up hepatic vasculature

1. hepatic artery
2. hepatic portal vein
3. von kupffer cells
4. central vein


what is the space of Disse?

it separates hepatocytes from endothelial cells and drains to portal lymphatic vessels


what are von kupffer cells

they line sinusoids within the liver along the endothelial cells. they are macrophage-like and phagocytose erythrocytes


what does the central vein do?

drain sinsuoids


which animals lack a gall bladder?

horse and rat


what are the tunics within the gall bladder

mucosa - simple columnar epithelium, folds when empty
muscularis - smooth muscle


cell types in exocrine pancreas

1. serous acinar cells - secrete zyogmen granules containing enzymes
2. centroacinar cells - line acinus
3. cuboidal epithelium lines intralobular and interlobular secretory ducts
4. larger ducts may contain goblet cells or mucous glands


cell type of the avian esophagus and crop

made up of keratinized stratified squamous epithelium


what is the function of the crop

an esophageal diverticulum that serves as a storage organ. the lamina epithelialis produces crop milk which moistens food and is diagnostically useful


layers of the proventreniculus (glandular stomach)

mucosa - grooves (sulci); mucosal (rugosal) glands open into bases of the sulci
submucosa - glands open into excretory duct leading to papilla


layers of the ventriculus (gizzard)

mucosa - koilin, cornified secretory product
muscularis - smooth muscle and dense white fibrous connective tissue

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