Digestive System (Small intestine to Anal Canal) Flashcards
Small intestines
Plica cicularis (folds of Kerkring), villi, simple columnar with absorptive goblet cells, glands (crypts of Liebercuhn) in LP, microvilli
Large intestine
No villi, simple column with goblet, glands (Liebercuhn) in LP with mostly goblet
What are the 3 segments of the small intestine?
Duodenum, jejunum and illeum
What are the functions of the surface modifications?
To increase the surface area by:
2-3 x- plicae
10x-villi
20x- microvilli
Enterocytes
Apical surface is modified to form microvilli and covered by glycocalyx
Lateral surface forms junctional complex
Cytoplasm has all organelles (pinocycitic vesicles, coated vesicles, lysosomes)
Goblet cells
Unicellular
Produce mucus that provides protective coat to the surface epithelium
Villar core (villus)
Loose CT underlying epith. with:
Capillaries, central lacteal, smooth muscle cells
Crypts of Lieberkuhn
Tubular glands
Goblet, stem, enteroendocrine and paneth cells
Eosinophilic granules with lysosomes
Absent in dog and pig
Where are paneth cells?
Present in cattle and horses
Absent in dog and pig
Brunner’s glands in the duodenum
Found only in the initial and middle parts in the dog, cat, man and ruminants
Found beyond the duodenum in horse and pig
What is the function of Brunner’s gland?
Alkaline secretion that protects the duodenum from the acidic chyme
T. muscularis of the small intestine
Inner circular and outer longitudinal
Myenteric nerve plexis between the 2 layers
What the the functions of the intestinal mucosa?
Secretion of mucus
Breakdown of carbohydrates, proteins and lipids
Absorption of small molecules
Changes along the length of the small intestine
Decrease in # and height of plicae and villi
Increase in # and depth of crypts
Increase in # of lymphatic nodules and goblets
Increase in thickness of T. muscularis
What are the 3 segments of the large intestine?
Cecum, colon, rectum
What is formed in the cecum and colon Muscularis
In man, horse and pig outer longitudinal layers are modified to from bands called tenia
Rectum
goblets increase
Serosa becomes adventitia
Circular layers of muscularis form internal sphincter
Recto-anal junction
Rectal mucosa abruptly changes into cutaneous membrane
What are the 3 regions of the anal canal of the dog and pig?
Zona columnaris
Z. intermedia
Z. cutanea
Anal sacs
At junction between z. intermedia and cutanea
Surrounded by apocrine sweat glands (glands of anal sac)- accumulation of secretion causes pain in dogs
What are the main functions of the salivary glands?
Secrete saliva that lubricates food
Initiate carbohydrate digestion by amalyse enzyme
What are the 3 pairs of salivary glands?
Parotid, submandibular and sublingual
All consist of acini and ducts
What are the 3 types of acini?
Serous, mixed and mucous
Serous
Pyramidal cells with round nucleus
Basophilic cytoplasm and acidophilic zymogen granules
Ex: parotid gland
Mucous
Pyramidal cells with flattened and basally placed nucleus
Empty-appearing mucin droplets (glycoprotein)- H&E
Ex: zygomatic dog
Mixed
Central mucous acinus surrounded by serous demilune
Ex: mandibular in horse and sublingual in dog
Myoepithelial cells
In all 3 types of acini
Function: Accelerate secretion of saliva
What are the ducts of the salivary glands
Intercalated, striated and excretory
Intercalated ducts
Situated between acini and striated duct
Lined by simple squamous and simple low cuboidal
Striated ducts
Between intecalated and excretory duct
Lined by simple columnar cells with basal striations
Function: active transport of ions and water
Excretory ducts
In CT between lobules
Lined by stratified squamous to cuboidal to columnar
Function: Transport salivary secretion to the oral cavity
