Histology II: Digestive system Flashcards
Another name for the intestinal glands
Crypts of Lieberkühn
What 3 structures increase the absorptive surface area of the small intestine?
Circular folds, villi and microvilli.
Crypts of Lieberkuhn glands are composed of what?
a simple columnar epithelium
What five type of cells are found in intestinal mucosal epithelium?
enterocytes, endocrine cells, goblet cells, M (microfold) cells and paneth cells
What are paneth cells?
highly specialized secretory epithelial cells
located in the crypts of Lieberkühn
secrete antimicrobial substances.
What are M cells?
Microfold cells are modified enterocytes (intestinal epithelial cells) that cover lymphatic nodules.
Enterocytes primary function?
absorption
what are Goblet cells
unicellular mucin-secreting glands
What does Muscularis externa, consist of?
inner circularly and outer longitudinally arranged smooth muscle cells.
What structure is NOT found with the intestinal crypts in the large intestine?
no intestinal villi in large intestine
the mucosa of the large intestine is made up of?
simple columnar epithelium containing numerous goblet cells and few enterocytes.
what are the 4 layers of t. mucosa of the large intestine?
mucosal layer, lamina propria, muscularis mucosae and then by submucosa (after that, we move to the next tunic)
Name 6 functions of the liver
- degrades drugs and toxins
- bile production - is an exocrine function
- endocrine-like functions = its ability to modify the structure of many hormones
- involved in many metabolic pathways
- stores and converts several vitamins and iron
(Vitamin A, D, K) - produces most plasma proteins
From which 2 sources does the liver receive blood?
hepatic artery and hepatic portal vein
Describe liver structure.
parenchymal hexagonal hepatic lobules,
which in turn consist of hepatocytes oriented radially surrounded by connective tissue stroma,
sinusoid structures throughout
where do the sinusoids drain
central vein of hepatic lobule
In addition to endothelial cells, what lines the sinusoids.
Kupffer cells (macrophages)
what structure carries bile to interlobular ducts
Bile canaliculi
the portal triad is what
interlobular bile duct, -artery and -vein located grouped together in the interlobular tissue
what does the pancreatic exocrine process do
produces digestive enzymes and secretes them into the duodenum
what does the pancreatic endocrine process do
synthesizes and secretes the hormones insulin and glucagon into the blood
what do you call groups of pancreatic cells secreting insulin and glucagon?
islets of Langerhans
what divides the pancreas into lobules?
connective tissue septa
Each pancreatic lobule consists of many what
acini (sg. acinus)
what are the secretory cells of the acinus called
the acinar cells
the acinar cells are characterized by?
distinct subnuclear area (ergastoplasm),
and zymogen granules in the apical part of the cytoplasm.
Digestive system divided into what 3 main areas?
Oral cavity, digestive tract and auxiliary gland system.
What is the oral cavity lined by?
Stratified squamous epithelium.
How are papillae divided into 2 main groups (name the groups)?
Based on their function they are grouped as mechanical papillae and gustatory papillae.
Name the 5 main structures of the oral cavity.
Major-, minor salivary glands, tongue, tonsils and teeth.
Name 3 major salivary glands.
the parotid, submandibular, and sublingual gland
Name 5 minor salivary glands located in the submucosa.
the buccal, labial, lingual, molar, and palatine glands
What do the tonsils consist of?
Aggregations of lymphatic nodules.
Two alternate names for the tongue;
lingua or glossa (genioglossus)
What is the cellular composition of the tongue surface?
Stratified squamous epithelium.
On what area of the tongue can you find papillae?
On the anterior part.
Describe mechanic papillae.
Are cornified.
Describe gustatory papillae.
Are covered with taste buds.
Name the 5 types of papillae found in domestic animals.
circumvallate. conical, filiform, foliate, fungiform
Describe filiform papillae
they’re highly keratinized and sharply pointed.
They’re the smallest and most numerous of all papillae.
Describe fungiform papillae
are smooth with a rounded surface, have taste buds on their lateral surfaces
Describe conical papillae
conical shape, mechanical function
somewhat larger than fungiform papillae, no taste buds
Describe foliate papillae
are covered with non-keratinized stratified squamous epithelium.
They are leaf-shaped and defined by an invagination of the mucous membrane on their sides, many taste buds on their lat. surfaces, absent in ruminants
Describe circumvallate papillae
are the largest, many taste buds.
Serous von Ebner’s glands empty into the “moat” around these papillae
What are the 4 types of teeth in mammals?
(1) incisors, (2) canines, (3) premolars and (4) molars
What are the 3 specialized tissues that teeth consist of?
Enamel, dentine, cementum.
Describe enamel.
hardest substance of the body,
composed of enamel rods that span the entire thickness of the layer,
its a thin translucent layer of acellular mineralized tissue
Describe dentine.
a calcified material that forms most of the tooth substance.
Describe cementum.
Cementum is a thin layer of bone-like calcified tissue covering the dentin of the root of the teeth.
Unlike bone, cementum is avascular.
What anchors teeth to their alveolar pockets?
The periodontal ligament (membrane) which contains bundles of collagenous fibers.
What is found in the center of teeth?
The central pulp cavity (Pulp chamber) is the space within the tooth that is occupied by dental pulp.
Describe dental pulp.
A loose connective tissue that is richly vascularized and supplied by abundant nerves.
Name 3 supporting tissues of teeth.
Alveolar bone of the processes of the maxilla and mandible, periodontal ligaments and gingiva.
What produces teeth?
The bell-shaped enamel organ that surrounds the connective tissue dental papilla.
What is the dental papilla?
Is an embryonic-like tissue which forms the dental pulp.
What surrounds the dental organ and dental papilla?
A dental sac.
What is the inner and outer surface of the enamel organ covered by?
Inner surface covered by simple columnar epithelium that’s formed by the inner enamel cells.
Outer surface by flat outer enamel cells.
What is stellate reticulum?
enamel pulp, a group of cells located in the center of the enamel organ
Where is the stellate reticulum located and describe it.
in the center of the enamel organ of a developing tooth and is formed by interconnected star-shaped epithelial cells and jelly-like substance.
What is an odontoblast and what is its function?
A cell in the pulp of a tooth that produces dentine.
Where does formation of the dentine begin?
At the top of the dental papilla, where the connective tissue cells differentiate into odontoblasts.
Odontoblasts start to deposit the main matrix of the dentine on their apical surface.
What are ameloblasts?
A cell that takes part in forming dental enamel.
Where does formation of the enamel begin?
Above the tooth papilla
columnar ameloblasts develop and then produce enamel prisms at their apical surface.
What 3 tunics does the digestive tract walls consist of?
Tunica mucosa,
tunica muscularis (or muscularis externa)
and tunica adventitia or serosa
depending on structure and location in the body.
What 4 layers does tunica mucosa consist of?
Mucosal epithelium, lamina propria, muscularis mucosa, and submucosa.
What are the 3 principal functions of tunica mucosa?
Protection, absorption and secretion.
What does the secretory function of the mucosa provide?
Lubrication and delivers digestive enzymes, hormones and antibodies into the lumen of the alimentary canal.
What does lamina propria, 2nd layer of tunica mucosa, contain?
Glands and vessels that transport absorbed substances, and components of the immune system.
What is GALT?
gut-associated lymphatic tissue (GALT)
The diffuse lymphatic tissue and the lymphatic nodules related to the GI tract.
What does the muscularis mucosa form?
The boundary between innermost mucosa and submucosa.
What does submucosa consist of?
A dense, irregular connective tissue layer containing blood and lymphatic vessels, a nerve plexus
occasional glands in the esophagus and initial portion of the duodenum.
What does T. muscularis consist of?
Smooth muscle tissue.
What is the exception location for t.muscularis not consisting of smooth muscle?
The beginning part of the esophagus, where it’s formed by skeletal muscle tissue.
In what animals is all the esophageal muscle tissue skeletal?
In dogs and ruminants.
Name the 2 sublayers to t.muscularis.
Inner circular layer and outer longitudinal layer.
What is adventitia?
A connective tissue layer, which gradually merges with neighboring structures.
What is serosa?
called mesothelium
tissue made of serous membrane
a simple squamous epithelium,
with a small amount of underlying connective tissue.
Where are the parts of the digestive tract surrounded by adventitia?
Outside the peritoneal cavity (esophagus).
Where are the parts of the digestive tract enveloped by serosa?
The parts inside the peritoneal cavity (stomach, small intestine, large intestine).
What is the esophagus lined by?
Thick non-keratinized stratified squamous epithelium
and mucosal glands that lubricate and protect the luminal wall.
What are the 3 layers of the esophageal wall?
T. mucosa
T. muscularis externa (or T. muscularis)
T. adventitia
What 3 regions is the stomach divided histologically into and on what basis?
Cardiac-, pyloric- and fundic regions on the basis of the type of gland that each contains.
Describe the cardiac region of the stomach AKA the cardia.
The part near the esophageal orifice, which contains the cardiac glands and cardiac sphincter.
Describe the pyloric region of the stomach.
Pyloric region contains the pyloric glands. The pylorus is the opening from the stomach into the duodenum.
Describe the fundic region of the stomach.
Fundic region, the largest part of the stomach, which is situated between the cardia and pylorus and contains fundic or gastric glands.
What does the epithelium of the fundic mucosa consist of?
Simple columnar epithelium.
A term for groups of numerous gastric pits.
Foveolae
Name 3 morphological parts of a gastric gland.
isthmus, neck and base
What is the site of gastric epithelium regeneration?
The isthmus.
What does the neck of the gastric gland consist of?
Mucocytes (which produce mucus).
What do parietal cells produce?
Hydrochloric acid.
What cells make up the base of the fundic glands?
Parietal, chief cells, and endocrine cells (G cells).
What do chief cells produce?
The pepsinogen (breaks down protein).
What do G cells produce?
Gastrin hormone.
What does the lamina propria of the mucosa consist of?
Reticular connective tissue.
What does the muscularis mucosa consist of?
composed of smooth muscle
Which papillae types are mechanical?
conical, filiform
Which papillae types are gustatory?
circumvallate, foliate, fungiform
What extends into each omasal fold?
prominent lamina muscularis mucosa
-> which means that the submucosa that separates the lamina muscularis mucosa from the tunica muscularis is less developed.
How does the lamina propria mucosa of the omasum differ from the rumen and reticulum?
Is thinner and less developed
Describe the internal surface of the omasum.
Has numerous folds, “leaves” or laminae, that are oriented along the longitudinal plane (laminae omasi)
Describe the reticular crests.
project vertically into the lumen, they fuse or anastomose with one another in a symmetrical manner, forming ridges that give a honeycomb or reticulate appearance.
What is the inner surface of rumen like?
The tunica mucosa is lined by keratinized stratified squamous epithelium that has numerous mucosal papillae.
Describe the proventriculus.
It is essentially aglandular, consisting of tissues that allow ingesta to be further macerated by mechanical and chemical means.
