Histology Of Pancreas And Spleen Flashcards
The pancreas
Is a mixed —— and —— gland that produces both digestive enzymes and hormones:
The digestive enzymes are produced by cells of the larger ——- portion
The hormones are synthesized in clusters of endocrine epithelial cells known as ——
Is a mixed exocrine-endocrine gland that produces both digestive enzymes and hormones:
The digestive enzymes are produced by cells of the larger exocrine portion
The hormones are synthesized in clusters of endocrine epithelial cells known as pancreatic islets (islets of Langerhans)
•the pancreas
A thin capsule of ——- covers the pancreas and sends septa into it, separating the pancreas into ——
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A thin capsule of connective tissue covers the pancreas and sends septa into it, separating the pancreas into lobules
The exocrine pancreas
The exocrine portion of the pancreas is a ———- type of gland, similar in structure to which gland
The exocrine portion of the pancreas is a compound acinar gland, similar in structure to the parotid gland
The secretory acini
The secretory acini are surrounded by a ——— that is supported by a delicate sheath of reticular fibers and a rich capillary network
The secretory acini are surrounded by a basal lamina that is supported by a delicate sheath of reticular fibers and a rich capillary network
Differences between the pancreas and the parotid gland
Differences between the pancreas and the parotid gland
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The two glands can be distinguished histologically by:
The absence of striated ducts and the presence of the islets in the pancreas
The initial portions of intercalated ducts penetrate the lumen of the acini in the pancreas
Small pale-staining centroacinar cells constitute the intraacinar portion of the intercalated duct and are found only in pancreatic acini
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Pancreatic acinus
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Each exocrine acinus of the pancreas is composed of several —— cells surrounding a very small lumen
The acinar cells are very (polarized/unpolarized?) , with a —— nucleus, and are typical —— -secreting cells
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Intercalated ducts merge to form larger ——— ducts lined by —— epithelium
There are no ——- ducts in the pancreas
The number of zymogen granules present in each cell varies and is maximal in animals that have ——
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Pancreatic acinus
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Each exocrine acinus of the pancreas is composed of several serous cells surrounding a very small lumen
The acinar cells are very polarized, with a spherical nucleus, and are typical protein-secreting cells
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Intercalated ducts merge to form larger interlobular ducts lined by columnar epithelium
There are no striated ducts in the pancreas
The number of zymogen granules present in each cell varies and is maximal in animals that have fasted
Pancreatic juice
Pancreatic juice is rich in —— ions and digestive enzymes including:———
The proteases are stored as inactive zymogens in the ———of acinar cells
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Production of ———by the acinar cells, prevents the pancreas from digesting itself
After secretion trypsinogens are cleaved and inactivated by ——— only in the lumen of the small intestine, generating trypsins which activate the other proteases in a cascade
Pancreatic juice
Pancreatic juice is rich in bicarbonate ions (HCO3-) and digestive enzymes including:
Several proteases (trypsinogens, chymotrypsinogen, proelastases, protease E, Kallikreinogen, procarboxipeptidases),
α-amylase
Lipases and
Nucleases (DNAase and RNAase)
The proteases are stored as inactive zymogens in the secretory granules of acinar cells
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Production of protease inhibitors by the acinar cells, prevents the pancreas from digesting itself
After secretion trypsinogens are cleaved and inactivated by enterokinase only in the lumen of the small intestine, generating trypsins which activate the other proteases in a cascade
Control of pancreatic secretions
Pancreatic secretion is controlled mainly through two polypeptide hormones- —— and ——
They are produced by —— cells of the intestinal mucosa
The ——nerve also stimulates pancreatic secretion and the autonomic system works in concert with the hormones to control pancreatic secretion
Acid and partially digested food in the gastric chyme enters the duodenum and stimulates local release of —— and ——
—— promotes the exocytosis of zymogens and enzymes from the pancreatic acinar cells
Secretin causes acinar and duct cells to add —— and —— ions to the secreted proteins:
Thus producing an abundant alkaline fluid
This fluid neutralizes the ———and allows the pancreatic enzymes to function at their optimal pH
The coordinated action of both hormones provides for proper secretion of enzyme- rich, alkaline pancreatic juice
Control of pancreatic secretions
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Pancreatic secretion is controlled mainly through two polypeptide hormones- secretin and cholecystokinin (CCK)
They are produced by enteroendocrine cells of the intestinal mucosa
The vagus (parasympathetic) nerve also stimulates pancreatic secretion and the autonomic system works in concert with the hormones to control pancreatic secretion
Acid and partially digested food in the gastric chyme enters the duodenum and stimulates local release of secretin and CCK
CCK promotes the exocytosis of zymogens and enzymes from the pancreatic acinar cells
Secretin causes acinar and duct cells to add water and bicarbonate ions to the secreted proteins:
Thus producing an abundant alkaline fluid
This fluid neutralizes the acidic chyme and allows the pancreatic enzymes to function at their optimal pH
The coordinated action of both hormones provides for proper secretion of enzyme- rich, alkaline pancreatic juice
————— - the proenzymes may be activated and digest pancreatic tissues, leading to very serious complications. Possible causes include infection, gallstones, alcoholism, drugs and trauma
Acute necrotizing pancreatitis- the proenzymes may be activated and digest pancreatic tissues, leading to very serious complications. Possible causes include infection, gallstones, alcoholism, drugs and trauma
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In conditions of extreme malnutrition such as kwashiorkor, pancreatic acinar cells and other active protein-secreting cells atrophy and lose much of their rough ER, hindering production of digestive enzymes
The spleen
Is the largest single accumulation of ——tissue in the body
It is the only lymphoid tissue involved in ——, thereby making it an important organ in defense against blood-borne antigens
It is also the main site of destruction of ——
Is the largest single accumulation of lymphoid tissue in the body
The spleen
It is the only lymphoid tissue involved in filtration of blood, thereby making it an important organ in defense against blood-borne antigens
It is also the main site of destruction of aged erythrocytes
It is a production site of antibodies and activated lymphocytes which are delivered to the blood
Any inert particles in the blood are actively phagocytosed by spleen macrophages
The spleen is surrounded by a capsule of dense connective tissue from which emerge ——— which partially subdivide the parenchyma or splenic pulp
Large trabeculae originate at the —— on the medial surface of the spleen
The spleen
These trabeculae carry —— and —— into the splenic pulp as well as —— that bring blood back into the circulation
Lymphatic vessels in the splenic pulp also leave through the hilum via the trabeculae
The spleen is surrounded by a capsule of dense connective tissue from which emerge trabeculae which partially subdivide the parenchyma or splenic pulp
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Large trabeculae originate at the hilum on the medial surface of the spleen
The spleen
These trabeculae carry nerves and arteries into the splenic pulp as well as veins that bring blood back into the circulation
Lymphatic vessels in the splenic pulp also leave through the hilum via the trabeculae
Splenic pump
The spleen is composed of reticular tissue containing:
The spleen is composed of reticular tissue containing:
Reticular cells
Many lymphocytes and other blood
cells
Macrophages and
Antigen presenting cells (APCs)
Splenic pulp
The splenic pulp has 2 components:——
The splenic pulp has 2 components: White pulp
Red pulp
Splenic pulp
The white pulp are small masses consisting of ———— and the ———
The red pulp consists of ———and ——
The white pulp are small masses consisting of lymphoid nodules and the periateriolar lymphoid sheaths
Splenic pulp
The red pulp consists of blood-filled sinusoids and splenic cords
White pulp
The splenic artery divides inside the hilium, branching into small——arteries that travel in the ——
They leave the trabeculae and enter the parenchyma as arterioles enveloped by a sheath of (T/B?) lymphocytes, called—-
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The spleen is specialized to process blood therefore it’s microvasculature is very important
The white pulp
The splenic artery divides inside the hilium, branching into small trabecular arteries that travel in the trabeculae
They leave the trabeculae and enter the parenchyma as arterioles enveloped by a sheath of T lymphocytes, the periateriolar lymphoid sheath (PALS), part of the white pulp
Periarteriolar lymphatic sheath
Surrounded by the PALS, these vessels are known as ———
After coursing through the parenchyma for variable stretches, the PALS receive large numbers of lymphocytes, mostly (B/T?) cells and may form ———
In these nodules the arteriole, although occupying an ——- position, is still called the central arteriole
Periarteriolar lymphatic sheath
Surrounded by the PALS, these vessels are known as central arterioles
After coursing through the parenchyma for variable stretches, the PALS receive large numbers of lymphocytes, mostly B cells and may form lymphoid nodules
In these nodules the arteriole, although occupying an eccentric position, is still called the central arteriole
White pulp
During its passage through the white pulp, this central arteriole sends off smaller branches that supply the surrounding lymphoid tissue
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After leaving the white pulp, the sheath of lymphocytes slowly thins and the central arteriole subdivides to form straight ———
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Some of the capillaries that emerge from these penicillar arterioles are sheathed with ——-,——- and ——-, whose functional significance is not clear
During its passage through the white pulp, this arteriole sends off smaller branches that supply the surrounding lymphoid tissue
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After leaving the white pulp, the sheath of lymphocytes slowly thins and the central arteriole subdivides to form straight penicillar arterioles
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Some of the capillaries that emerge from these penicillar arterioles are sheathed with reticular cells, macrophages and lymphocytes, whose functional significance is not clear
The marginal zone
Surrounding the lymphoid nodules is a marginal zone consisting of many blood sinuses and lymphoid tissue
The marginal zone contains:
The marginal zone plays an important role in the ——— activities of the spleen
Surrounding the lymphoid nodules is a marginal zone consisting of many blood sinuses and lymphoid tissue
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The marginal zone contains: Lymphocytes
Many macrophages, and Abundance of blood antigens
The marginal zone
The marginal zone plays an important role in the immunological activities of the spleen
Is composed almost entirely of splenic cords and venous sinusoids
The splenic cords contain a network of reticular cells or reticular fibers that support:
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s composed almost entirely of splenic cords and venous sinusoids
The red pulp
The splenic cords contain a network of reticular cells or reticular fibers that support:
T and B lymphocytes Macrophages Plasma cells and
Many blood cells (erythryocytes, platelets, and granulocytes)
The splenic cords are separated by wide, irregularly shaped ———
Unusual elongated endothelial cells called ——- cells, line the splenic sinusoids oriented in parallel with the sinusoid’s ——-
The highly permeable splenic sinusoids are surrounded by very incomplete ——
Splenic sinusoids
The splenic cords are separated by wide, irregularly shaped sinusoids
Unusual elongated endothelial cells called Stave cells, line the splenic sinusoids oriented in parallel with the sinusoid’s blood flow
The highly permeable splenic sinusoids are surrounded by very incomplete basal laminae
Splenic sinusoids
Only —— cells are able to pass easily from the red pulp cords into the lumen of the sinusoids
Splenic cords and sinusoids are often difficult to distinguish microscopically because:
Only flexible cells are able to pass easily from the red pulp cords into the lumen of the sinusoids
Splenic cords and sinusoids are often difficult to distinguish microscopically because:
The splenic cords are infiltrated with red blood cells and the lumen of the splenic sinusoids are very small, and is often blood-filled
Blood flow in the red pulp
Blood flow through the splenic red pulp can take two routes:
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Blood flow in the red pulp
Blood flow through the splenic red pulp can take two routes:
Closed circulation
Open circulation
Blood flow in the red pulp
In the closed circulation, the penicillar arterioles/capillaries branching from them connect directly to the ——— so that blood is always enclosed by vascular endothelium
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In open circulation, other penicillar arterioles which are open-ended, dump blood directly into the ——- of the ——
In the closed circulation, the penicillar arterioles/capillaries branching from them connect directly to the sinusoids so that blood is always enclosed by vascular endothelium
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In open circulation, other penicillar arterioles which are open-ended, dump blood directly into the stroma of the splenic cords
Blood flow in red pulp
In this route, plasma and formed elements of blood reenter the vasculature by passing between the —— cells of sinusoids, which presents no problem for platelets, leukocytes, and healthy flexible erythrocytes
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However, after their normal lifespan of —— days affete erythrocytes undergo membrane changes becoming swollen and less flexible, signaling their selective engulfment by macrophages in the ——
In this route, plasma and formed elements of blood reenter the vasculature by passing between the stave cells of sinusoids, which presents no problem for platelets, leukocytes, and healthy flexible erythrocytes
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However, after their normal lifespan of 120 days affete erythrocytes undergo membrane changes becoming swollen and less flexible, signaling their selective engulfment by macrophages in the splenic cords
Blood flow in red pulp
From the sinusoids, blood proceeds to the ——— that join together and enter the trabeculae, forming the —— veins
The —— vein originates from these vessels and emerges from the hilum of the spleen
The trabecular veins do not have —— in their wall and resemble channels hollowed out in the trabecular connective tissue and lined by endothelium
From the sinusoids, blood proceeds to the red pulp veins that join together and enter the trabeculae, forming the trabecular veins
The splenic vein originates from these vessels and emerges from the hilum of the spleen
The trabecular veins do not have muscle in their wall and resemble channels hollowed out in the trabecular connective tissue and lined by endothelium
——— – surgical removal of the spleen following abdominal injury that results in rupture of the spleen capsule, certain anemias and platelet disorders
Splenectomy – surgical removal of the spleen following abdominal injury that results in rupture of the spleen capsule, certain anemias and platelet disorders
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The risk of infection may be higher in a splenectomized individual
