Digestive System Flashcards
Portal vein
- brings blood from the intestine and carries absorbed food
Hepatic artery
- supplies the oxygenated blood
Blood supply to the Liver
- Portal vein and Hepatic Artery
- Hepatic Sinusoids
- Central vein
- Hepatic Vein
5 Caudal Vena Cava
Layers of the Cheeks
- Outer skin
- Middle muscular Layer (buccinator muscle)
- Internal Mucosa
Chief Cells
- secrete pepsinogen
- pepsinogen transformed into pepsin by HCl
Peyers Patches
- found in the submucosa of the small intestine
- particularly the ileum
Peyers Patches
- large aggregated lymphatic nodules
Hepatocytes
- polyhedral cells with 3 surfaces
Hepatocytes surfaces
- Microvillus
- Canalicular
- Contact surface
Microvillus surface
- faces the perisinusoidal space
Canalicular surface
- borders the bile canaliculi
Contact surface
- between the adjacent hepatocytes
- opposed cells membranes may have gap junctions and desmosomes
Lips Mucosa lined by:
- stratified squamous epithelium
Ruminants and Horses
- Lips Mucosa: Stratified squamous keratinized
Carnivore and Pigs
- Lips Mucosa: Stratified squamous non-keratinized
Cheeks Mucosa is lined by:
- stratified squamous which may or may not be keratinized
Cheek Mucosa in Ruminants
- Mucosa is studded with conical buccal papillae
Dogs
- lamina muscularis is thick and complete in the small intestine
Rugae
- numerous transverse ridges in the hard palate
Palatine Glands
- gland located in the caudal part of the hard palate
Buccal Glands
- gland located in the propriasubmucosa of the cheeks
Labial Gland
- gland located in the propriasubmucosa of the lips
Dental Pad
- found in ruminants
- heavily keratinized stratified squamous epithelium overlying a thick layer of dense irregular CT
Soft Palate lined by:
- stratified squamous epithelium
Pigs and Horses
- palantine tonsils
- derived from the soft palate
Cow Hard Palate
- Dental Pad
- Buccal Papillae
- Palatine Raphe
- Rugae
Dog Hard Palate
- Rugae
2. Soft Palate
Functions of the Tongue
1. eating, drinking, vocalization 2. muscular and mobile 3. epithelial specializations 4. sensitive and highly innervated 5. contains chemoreceptor sites 6. thermoregulation
Tongue
- muscular organ covered by a mucosa
Tongue is lined by
- stratified squamous epithelium
- keratinized on the dorsal surface
- nonkeratinized on the ventral surface
Intrinsic Lingual Muscle of the Tongue
- bundles of skeletal muscle
- arranged in a longitudinal, transverse and perpendicular direction
Lingual Papillae
- on the dorsal surface of the tongue
- serve either a mechanical or gustatory function
Mechanical Lingual Papillae
- Filiform
- Conical
- Lenticular
Gustatory Lingual Papillae
- Fungiform
- Vallate
- Foliate
Mechanical Lingual Papillae
- facilitate the movement of ingesta
- all keratinized stratified squamous
Gustatory Lingual Papillae
- have taste buds
- all nonkeratinized stratified squamous
Lips
- devoid of hair follicles, sweat and sebaceous glands
Filiform Papillae
- slender, thread-like structures that project above the surface of the tongue
Filiform Papillae Species Differences: 1.Ruminants and Cats 2. Horses
- filiform papillae is very well developed
- filiform papillae is very fine keratinized threads
Conical Papillae
- in dogs, cats and pigs located on the root of the tongue
- in ruminants located on the torus linguae
Lenticular Papillae
- flattened, lens shaped projection
- present on the torus liguae of ruminants
Fungiform Papillae
- mushroom shaped
- contains taste buds on the upper surface
Horse and Cow
- in fungiform papillae taste buds are sparse
Sheep and pig
- in fungiform papillae taste buds are more numerous
Carnivores and Goats
- in fungiform papillae taste buds are abundant
Vallate Papillae
- numerous taste buds occur in the epithelium on the papillary side of its sulcus
Foliate Papillae
- taste buds are located on the sides of the folds
Vallate Papillae
- large, flattened structures completely surrounded by an epithelium lined
sulcus
Foliate Papillae
- they are parallel folds of the lingual mucosa located on the caudo-lateral margin of the tongue
Ruminants
- the foliate papillae is absent
Cats
- the foliate papillae is rudimentary
- no taste buds
Taste Buds
- consists of a cluster of spindle-shaped epithelial cells that extend from the BM to a small opening, the taste pore, at the epithelial surface
3 Types of Taste Bud Cells
- Sustentacular Cells
- Gustatory Cells
- Basal Cells
Non-myelinated afferent nerve fibers (taste receptors)
- closely associated with the gustatory cells
Lyssa
- a cordlike structure present in the tongue of carnivores
Torus Linguae
- a large prominence on the caudal part of the dorsal surface of the ruminant tongue
Dorsal Lingual Cartilage
- a mid-dorsal fibroelastic cord with hyaline cartilage
- present inside the tongue of horses
Highly Mineralized Structure (outer part)
- Enamel
- Dentine
- Cementum
Enamel
- produced by ameloblasts
- hardest structure in the body
Enamel Composition
- 99% mineral (hydroxyaptite)
- 1% organic matter
Dentine
- produced by odontoblasts
Dentine Composition
- 70% Minerals
- > mainly hydroxyapatite, some carbonate, magnesium and fluoride
- 30% Organic material
- > mainly collagen fibrils and glycoprotein
Cementum
- resembles bone
Cementum Composition
- lamellae oriented parallel to the surface of the tooth
- cementoytes occupy the lacunae
Cemento-alveolar (sharpey’s) fibers
- bundles of collagen fibers
- form the peridontal ligament
Peridontal ligament
- anchors the tooth in the alveolus (to bone)
Pulp Cavity (central part)
- Dental Pulp
- A core of CT
- Blood vessels and nerves
Brachydont Teeth
- short and cease to grow after eruption is complete
- have a crown, neck and root
Brachydont Teeth Species
- all teeth of carnivores
- incisors of ruminants
Hypsodont Teeth
- much longer and grow throughout life
- do not have a crown or neck
- both cementum and enamel cover the length of the tooth
Hypsodont Teeth Species
- cheek teeth in ruminants
- all permanent teeth in horses
- incisors/canines of pigs and elephants
Major Salivary Glands
- Parotid
- Mandibular
- Sublingual
- Zygomatic (carnivores)
Parotid Salivary Gland
- predominantly serous
- compound acinar gland
- occasionally isolated mucous secretory units may occur in dogs and cats
Mandibular Salivary Gland
- seromucous
- compound tubuloacinar gland
- predominance of mucous acini and serous demilune
- Cells of the mucous secretory unit are filled with mucinogen
Cells of the mucous secretory Unit
- are filled with mucinogen
Sublingual Salivary Gland
- seromucous
- compound tubuloacinar gland
Sublingual Salivary Gland: Cattle, Sheep and Pigs
- almost entirely mucous with relatively few serous demilune
Sublingual Salivary Gland: Dog and Cat
- contains clusters of serous acini in addition to typical mucous and serous demilunes
- striated and intercalated ducts are not predominant
Sublingual Salivary Gland: Horse, Ruminants and Pigs
- striated and intercalated ducts are well developed
Zygomatic Salivary Gland
- only in carnivores
Minor Salivary Glands
- Labial
- Lingual
- Buccal
- Palatine
- Molar
- cats
Molar Salivary gland
- cats
- similar to zygomatic salivary gland
General: Tunica Mucosa Layers
- Epithelium
- Lamina propria
- Lamina Muscularis
General: Tunica Submucosa Layer
- Connective Tissue
- Glands
- Meissner’s Plexus
General: Tunica Muscularis Layer
- Smooth or skeletal muscle
2. Myenteric (Auribach’s) plexus
General: Tunica Serosa/Adventitia Layers
- outer most layer
Esophagus Tunica Mucosa: epithelium
- stratified squamous
1. Dog - nonkeratinized
2. Pigs and Horses - slightly keratinized
3. Ruminants - Highly keratinized
Esophagus Tunica Mucosa: Lamina Muscularis
- contains ONLY longitudinally orientated smooth muscle bundles
Esophagus Tunica Submucosa: Horses, cats and ruminants
- seromucous gland located at the pharyngoesophageal junction
Esophagus Tunica Submucosa: Pigs
- seromucous gland located at the cranial half of the esophagus
Esophagus Tunica Submucosa: Dog
- seromucous gland located throughout its length
Esophagus Tunica Muscularis: Ruminants and Dog
- entirely striated and skeletal
Esophagus Tunica Muscularis: Horse
- Skeletal muscle makes up the cranial 2/3, but gradually changes to smooth muscle in caudal 1/3
Esophagus Tunica Muscularis: Cats
- Skeletal muscle may extend 4/5 of the length before changing to smooth muscle
Esophagus Tunica Muscularis
- inner circular layer thickens at the cardia and forms the cardiac sphincter
- > prominent in horses
Esophagus Tunica Adventitia
- in the cervical region
Esophagus Tunica Serosa
- in the thoracic and abdominal region
Horses, Pigs and Carnivores Stomach
- simple stomach
Ruminants Stomach
- compound stomach
Glandular Region of the stomach
- abomasum
Nonglandular region of the stomach
- rumen, reticulum and omasum
Rumen Tunica Mucosa: epithelium
- stratified squamous keratinized
Rumen and Reticulum Tunica Mucosa: Lamina Muscularis
- lamina muscularis is absent
Reticulum Tunica Mucosa: Lamina propria
- blends with submucosa to form the propria-submucosa
- formed by a feltwork of collagen/elastic
fibers - a band of smooth muscle is located in the upper part of the reticular fold
Reticular Groove
- extends from the cardia to the reticulo-omasal orifice
- functional in young animals
- > creates a channel that allows the milk to bypass the rumen and reticulum
Omasum Tunica Mucosa
- mucosa has characteristic omasal laminae or ‘leaves’ which are studded with macrostopic papillae that help in grinding of the food
Omasum Tunica Mucosa: Lamina Muscularis
- forms a thick layer just beneath the lamina propria on both sides of the laminae
Nonglandular region of the stomach in carnivores
- absent nonglandular region
Nonglandular region of the stomach in pigs
- small nonglandular region
Horses Nonglandular region of the stomach
- nonglandular region is separated from the glandular region by the margoplicatus
Ruminants Nonglandular region of the stomach
- nonglandular region (forestomach) is the most developed
Glandular Region(Abomasum) Tunica Mucosa
- mucosa has extensive gastric folds that will flatten as the stomach fills
- the surface has small invaginations call gastric pits which are continuous with the gastric glands
Glandular Region(Abomasum) Tunica Mucosa: epithelium
- mucosal surface and gastric pits are lined by simple columnar epithelium
Abomasum is divided into 3 regions
- Cardiac Gland Region
- Fundic Gland Region
- Pyloric Gland Region
Cardiac Gland Region
- most developed in pigs
- glands that are relatively short, simple branched, coiled tubular glands that release a mucous secretory product
- empty into relatively shallow gastric pits
Fundic Gland Region
- straight, branched tubular glands that extend into the lamina muscularis
- short neck, long body and a lightly dilated blind end
Four distinct cell types comprise the secretory epithelium of the Fundic Gland Region
- Mucus neck cells
- Chief Cells
- zymogen cells - Parietal Cells
- Endocrine Cells
Mucus Neck Cells
- fundic gland region
- occupy the neck of the gland
Chief Cells
- fundic gland region
- zymogen cells
- most numerous cells
- secrete pepsinogen
- > which is transformed into pepsin by hydrochloric acid
Parietal Cells
- fundic gland region
- larger and less numerous than chief cells
- occur singly
- contains an abundance of carbonic anhydrase that helps in the formation of hydrochloric acid
Endocrine Cells
- fundic gland region
- argentaffin cells
- responsible for the production of GIT hormones
- best demonstrated by silver salt
- their secretory product is released directly into capillaries
Pyloric Gland Region
- branched, coiled tubular glands that are relatively shorter than other gastric glands
- the gastric pits are considerably deeper than other glands
Small Intestine specialized structures
- mucosal folds (plicae circulares) in the cranial 2/3
- surface of the mucosa is covered with finger-like projections (intestinal villi)
- absorptive surface is further increased by the microvilli on the free surface of the simple columnar epithelial cells
Small Intestine Tunica Mucosa: Epithelium
- simple columnar
Small Intestine Tunica Mucosa
- numerous goblet cells
- the density of the goblet cells is greater in the caudal part of the SI (ileum)
- crypts of liberkuhn
- paneth cells
- enteroendocrine (argentaffin) cells
Crypts of Liberkuhn
- intestinal glands
- simple branched tubular invaginations at the base of the villi
- give rise to the columnar and goblet cells
Paneth cells
- near the base of the intestinal gland, or the Crypts of Liberkuhn
- produce peptidase and lysozyme (antibacterial compound)
Small Intestine of Ruminants and Horses
- paneth cells are present
Small Intestine Tunica Mucosa: Lamina Propria
- forms the core of the villi
- diffuse lymphatic tissue or lymphatic nodules (Peyer’s Patches) are present throughout the SI and increase in number towards the ileum
- lacteal
Lacteal
- located in the lamina propria of the small intestine
- a single lymphatic capillary
- located in the center of the villus
Small Intestine Tunica Mucosa: Lamina Muscularis
- thin and incomplete
- > except in the dog it is complete and thicker
Small Intestine Tunica Submucosa
- tubuloalveolar submucosal glands (Brunner’s Gland) are located mainly in the duodenum
Brunner’s Glands
- located mainly in the duodenum
Brunner’s Glands in ruminants and dogs secrete
- Brunner’s glands secrete mucous glands
Brunner’s Glands in pigs and horses secrete
- Brunner’s glands secrete serous glands
Brunner’s Glands in cats secrete
- mixed glands
Peyer’s Patches
- large aggregated lymphatic nodules
- mainly present in the ileum
Jejunum
- does not have glands or patches
- has CT in the submucosa !
Small Intestine Tunica Muscularis
- thickest in horses
Large Intestine characteristics
- No villi, only crypts
- longer, less-coiled, simple tubular glands with many goblet cells
- No paneth cells
- No plica circulares (mucosal folds)
Large Intestine: Cecum
- lots of lymphatic nodules scattered throughout its length
Large Intestine: Colon
- the mucosa is substantially thicker because of the increased length of intestinal glands
Large Intestine of Pigs and Horses
- have Taenia
- > outer longitudinal layer of the tunica muscularis that form flat muscle bands containing numerous elastic fibers
Large Intestine: Rectum
- increased number of goblet cells
Anal Canal in pigs and carnivores
- Columnar Zone
- Intermediate Zone
- Cutaneous Zone
Columnar Zone of the anal canal
- contains longitudinal folds
- > anal columns
- epithelium is stratified squamous nonkeratinized
Intermediate Zone of the anal canal
- a narrow strip between the columnar and cutaneous zone
- epithelium is stratified squamous nonkeratinized
Cutaneous zone of the anal gland
- lined by stratified squamous keratinized epithelium
Anal Sacs in carnivores
- bilateral invaginations of anal mucosa
- with modified sweat glands
Liver
- largest gland in the body
- high regenerative power
Functions of the Liver
- Bile secretion
- Metabolism of protein, CHOs, Lipids, hemoglobin and drugs
- Hemopoiesis
- in fetal - Phagocytosis
- Detoxification
Glisson’s Capsule of the Liver
- liver is covered by a typical serosa overlying a thin CT capsule called this
The interlobar CT of the Liver
- prominent in portal areas containing branches of
1. Hepatic Artery
2. portal vein
3. Bile duct
4. Lymphatics
Interlobar CT septa of the Liver
- in most species is scant
- except for the pig it is distinct
Liver Lobule Types
- Classic Lobules
- Portal Lobules
- Liver Acinus
Classic Lobules
- the anatomical unit of the liver
- these lobules are roughly hexagonal
- the portal area is present between 3 adjacent lobules
Portal Lobules
- a functional unit in relation to the bile secretion
- a triangular shaped area
- the portal area is in the center
- 3 central veins of the classic lobules at the peripheral angles
Liver Acinus
- a functional unit in relation to the metabolic activity
- roughly diamond-shaped area made of parts of:
- > the 2 classic lobules
- > 2 central veins at the apposing points
Bile canaliculus of the Liver
- is simply an expanded intercellular space between the membranes of adjacent hepatocytes
Bile Flow (small to large) of the Liver
- Bile canaliculi
- Bile Ductules
- Interlobular Bile Ducts
- Hepatic Ducts
- Bile Duct (common Bile duct)
Hepatic Sinusoids of the Liver
- carry blood from the terminal branches of the hepatic artery and portal vein to the central vein
- lined by endothelial cells and stellate macrophages (Kupffer cells)
Kupffer Cells
- they are stellate macrophages (phagocytic cells) of the liver
- lines the hepatic sinusoids in the liver
Gall Bladder in Horses, rats, deer, pigeons
- gall bladder is absent
Function of Gall Bladder
- Storage
- Concentration
- Acidification
- Delivery of Bile
Gall Bladder Structure
- the mucosa is thrown into numerous folds in the contracted (empty) state
- lined by simple columnar epithelium
Gall Bladder in cattle
- goblet cells are present in the gall bladder
Exocrine Pancreas
- presence of centroacinar cells in the lumen of the secretory acinus
- Intralobular Ducts are not stratified
Centroacinar cells
- present in the pancreas
- in the lumen of the secretory acinus
- secrete bicarbonate which raise the pH of the intestinal contents
Lamellar (Paccian) corpuscles
- frequently present in the pancreas of cats
Avian Oral Cavity
- a cornified beak is attached to the upper and lower jaw bone
- NO teeth
Avian Oral Cavity Tunica Mucosa: Epithelium
- stratified squamous epithelium
Avian Oral Cavity Tunica Mucosa: Lamina Propria
- blends with the propria-submucosa
- contains lots of diffuse lymphatic tissue
- > no lymph nodes
- salivary glands
Salivary Glands in Birds
- all are branched tubular mucous glands
Avian Tongue
- stratified squamous keratinized
- contains an entoglossal bone
Avian Esophagus
- stratified squamous keratinized
Avian Crop
- sac like diverticulum of the esophagus
- it’s a storage organ where the ingested food is moistened by mucous secretion of
the esophageal and crop gland
Brooding Steps of the Crop
- the crop secretes crop milk (desquamated lipid-laden cells)
- mixes with the ingested food
- mixture is regurgitated
- fed to the nestling
Avian Stomach 2 parts
- Proventriculus
2. Ventriculus
Avian proventriculus
- glandular portion of avian stomach
- mucosa has macroscopic papillae
- oxynticopeptic cells
Oxynticopeptic cells
- in the proventriculus of the avian stomach
- produce pepsin and hydrochloric acid
Avian Ventriculus
- the gizzard
- responsible for grinding ingesta
Avian ventriculus Tunica Mucosa
- lined by the cuticle which is a secretory product of the mucosal gland
Avian ventriculus Tunica Muscularis
- smooth muscle cells
- criss crossed by bands of dense white, fibrous CT
Avian Small Intestine: Lamina Propria
- contain large amounts of diffuse and nodular lymphatic tissue
Avian Small Intestine: Tunica Submucosa
- contain large amounts of diffuse and nodular lymphatic tissue
- duodenal submucosa glands are absent
Avian Large Intestine
- 2 ceca are present at the ileocolic juntion
Cecal Tonsils
- in the large intestine
- adult birds have these
- large mass of diffuse and nodular lymphatic tissue that infiltrates the lamina propria and the submucosa at the cecal orifice
Avian Large Intestine: The proximal part of the Ceca and Colon
- Villi in the large intestine
Cloaca Parts (cranial to caudal)
- Coprodeum
- Urodeum
- Proctodeum
Avian Cloacal Bursa
- bursa of Fabricius
- sac like diverticulum of proctodeum in birds only
- plicae (tall mucosal folds)
- pseudostratified columnar epithelium
- lymphoid organ/immune system organ
- B lymphocytes differentiate here
- > into plasma cells when activated
Avian Vent
- The tunica mucosa of the vent is highly folded and lined by keratinized stratified squamous epithelium.
- Striated muscle of the tunica muscularis forms a sphincter
Portal Area
- Hepatic Artery
- Portal Vein
- Bile Duct
- Lymphatics