Histology Digestive Glands I

Front 1

Extrinsic glands of the digestive system are located...

Back 1

outside the wall of the alimentary canal
- deliver secretion into lumen via a system of Ducts

Front 2

Function of extrinsic glands:

Back 2

-Provide enzyme, buffers, emulsifiers, and lubricants for the digestive tract
-Provide hormones, proteins, globulins ...etc. to the remainder of the body

Front 3

Extrinsic glands include:

Back 3

Salivary glands (parotid, sublingual, submandibular)
Pancreas
Liver

Front 4

Salivary glands are:

Back 4

=exocrine glands in the mouth
-produce saliva (function in digestive, lubricating, protective)
-pH: 6.5-6.9

Front 5

Saliva is important in:

Back 5

buffering
evaporative cooling (in nonhuman species)

Front 6

3 pairs of the large salivary glands are:

Back 6

1. Parotid
2. Submandibular
3. Sublingual
-in addition to minor glands in mucosa and submucosa throughout the oral cavity --> secrete 10% of the total vol. of saliva

Front 7

Reduced function of the major salivary glands (due to diseases/radiotherapy) is associated with:

Back 7

caries - atrophy of the oral mucosa and speech difficulties (destroy bone structures i.e. teeth)

Front 8

Each major salivary gland is surrounded by:

Back 8

A capsule of connective tissue

Front 9

Organization of a compound gland:

Back 9

Main duct < Lobar duct < INTERlobular duct < INTRAlobular duct < Striated duct < Intercalated duct < Acinus

Front 10

What lines intralobular duct?

Back 10

Cuboidal to columnar

Front 11

What lines striated duct?

Back 11

Cuboidal to columnar

Front 12

What lines interlobular duct?

Back 12

Pseudostratified columnar

Front 13

What lines lobar duct?

Back 13

Columnar stratified

Front 14

What lines intercalated duct?

Back 14

Simple cuboidal

Front 15

Secretion of each gland can be:

Back 15

Serous (fluid)
Seromucous
Mucous (viscous)
*depending on its glycoprotein mucin content

Front 16

Saliva from the Parotids is:

Back 16

Serous & watery

Front 17

Submandibular and sublingual glands produce what type of secretion?

Back 17

Seromucous secretion
with mostly mucus from minor glands

Front 18

Saliva is modified in which way?

Back 18

Much Na+ & Cl- reabsorbed
Certain growth factors and digestive enzymes are added

Front 19

What are serous cells?

Back 19

Polarized protein-secreting cells
usually pyramidal in shape
broad base resting on basal lamina
narrow apical surface facing lumen

Front 20

Ajacent serous cells are joined by...

Back 20

Junctional complexes --> form a spherical mass of cells = Acinus

Front 21

Shape of acini and their duct system?

Back 21

like grapes attached to a stem

Front 22

Serous acinar cells produce:

Back 22

Digestive enzymes and other proteins

Front 23

Shape of the mucous cells:

Back 23

~cuboidal / columnar with nuclei pressed toward the bases of the cells

Front 24

What do the mucous cells contain?

Back 24

hydrophilic glycoprotein mucins
*important for the moistening and lubricating functions of the saliva

Front 25

Mucous cells are organized in what shape?

Back 25

most often tubules rather than acini
-produce mostly mucins

Front 26

Where are myoepithelial cells found?

Back 26

Inside the basal lamina of the secretory units
and (less in) the initial part of the duct system

Front 27

Myoepithelial cells are sometimes called...

Back 27

Basket cells

Front 28

Shape of the myoepithelial cells?

Back 28

1. those surrounding the secretory portion --> Well developed and branched
2. those associated with initial ducts --> spindle-shaped & lie parallel to the duct's length

Front 29

Function of the myoepithelial cells:

Back 29

- prevent distention of the endpiece when lumen fills with saliva
- contraction to accelerate secretion of the product

Front 30

Course of salivary glands:

Back 30

Secretory endpieces (serous acinus/mucous tubule) --> intercalated ducts --> striated ducts --> intralobular ducts --> interlobular ducts --> lobar ducts --> main duct

Front 31

Structure of the Columnar cells of striated ducts:

Back 31

Radial striations extending from the cell bases to the level of the nuclei
- striations consist of infoldings of the basal plasma membrane
*the folds increases cell surface area --> facilitate ion absorption & ion transport

Front 32

Columnar cells of striated ducts contain:

Back 32

numerous mitochondria aligned parallel to the infolded membranes which contain ion transporters

Front 33

Striated ducts converge and drain into ducts located in the CT septa and becomes...

Back 33

Interlobular ducts

Front 34

Epithelium of the ducts:

Back 34

Initiallly: pseudostratified/stratified cuboidal
Distal part: stratified columnar with a few mucous cells

Front 35

The main duct of each large salivary gland empties into...

Back 35

Oral cavity

Front 36

Epithelium of the oral cavity:

Back 36

Nonkeratinized-stratified squamous epithelium

Front 37

Vasculization of the salivary glands:

Back 37

- vessels and nerves enter the large salivary glands at a hilum
- a rich vascular and nerve plexus surrounds the secretory and ductal components of each lobule
- capillaries surrounding secretory endpieces --> imp for secretion of saliva (stimulated by autonomic n.s.)

Front 38

Parasympathetic stimulation of the salivary glands:

Back 38

- elicited by smell/taste of food
- provokes copious (=plenty) watery secretion with relatively little organic content

Front 39

Sympathetic stimulation of the salivary glands:

Back 39

- inhibits secretion --> dry mouth (often associated with anxiety)

Front 40

Name the different structures of ducts

Back 40

1. simple tubular
2. simple coiled tubular
3. simple branched tubular
4. simple branched acina

Front 41

Structure of this duct?

Back 41

left: compound tubuloacinar
right: compound tubular

Front 42

Structure of this duct:

Back 42

Compound acinar

Front 43

Know the location of the major salivary glands

Back 43

Front 44

Classification of parotid gland:

Back 44

Purely serous
branched acinar

Front 45

What forms the capsule of the parotid gland?

Back 45

by the continuation of superficial cervical fascia - mostly collagenous
--> forms broad bands of trabeculae (septa) that subdivide the gland into lobes and lobules

Front 46

Trabeculae of the parotid glands:

Back 46

convey blood and lymph vessels, ducts, and nerves into the substance of the gland
- contain fat cells in older individuals

Front 47

What type of gland is this?

Back 47

Parotid gland

Front 48

Acini of parotid glands:

Back 48

Composed of seromucous instead of purely serous cells (serous cells predominate)
-surrounded by myoepithelial cells
-contains lumen in the center

Front 49

Secretory portion of the parotid gland consists of:

Back 49

-Serous amylase-producing cells that store this enzyme in secretory granules
-intralobular (intercalated & striated) ducts
*slide stained with toluidine blue (PT)

Front 50

Structure of the Acinar cells:

Back 50

-Pyramidal cells
-apical aspects usually contain secretory granules
-nucleus is round and basally located
-cytoplasm contains extensive RER, well-developed golgi apparatus, numerous mitochondria

Front 51

Structure of the Myoepithelial cells:

Back 51

-Stellate-shaped
-cytoplasm is difficult to distinguish with LM
-with EM, they resemble smooth muscle cells and are contractile

Front 52

Red arrow is pointing to:

Back 52

nucleus of a myoepithelial cell

Front 53

Stensen’s Duct:

Back 53

- largest (main parotid duct)
- opens into the oral vestibule at the parotid papilla

Front 54

What kind of epithelium lines the Stensen's duct?

Back 54

Simple columnar or pseudostratified epithelium

Front 55

Mode of secretion is classified into:

Back 55

1. Merocrine (process of exocytosis)
2. Apocrine
3. Holocrine

Front 56

What are the smallest ducts

Back 56

Intercalated ducts
- lie interposed (between) among the acini (initial part of the duct system)

Front 57

What lines the intercalated ducts?

Back 57

Simple cuboidal epithelium

Front 58

Striated ducts are lined by:

Back 58

High cuboidal cells

Front 59

Structure of the striated ducts:

Back 59

- basal striations that parallel the longitudinal axis of the cell
- striations are due to deep infoldings of the basal plasma membrane (compartmentalize mitochondria)

Front 60

What type of gland is this?
Arrow are pointing to ...

Back 60

Parotid gland

Front 61

What do the granules of the parotid glands contain?

Back 61

-rich in proteins (proline-rich proteins)
-enzymes (amylase, peroxidase, lysozyme)
-proteins with antimicrobial activity (cystatins & hystatins)

Front 62

Structure of the parotid gland:

Back 62

-has the longest intercalated ducts
-myoepithelial cells at the periphery of each acinus
-CT & vessels surround the serous acini

Front 63

Classification of sublingual gland:

Back 63

-Contains both pure mucous & mixed secretory units
-Mixed, compound-branched tubuloacinar gland
*mucous cells predominate

Front 64

What type of cells does sublingual gland contain:

Back 64

Mucous cells that predominate with serous cells only present in demilunes on mucous tubules
-mucous cells resemble goblet cells of the intestinal epithelium

Front 65

Major salivary product of the sublingual gland is:

Back 65

mucus
-cells of the serous demilunes secrete amylase and lysozyme

Front 66

Shape/structure of the sublingual mucous cells:

Back 66

-Pyramidal
-flattened nuclei against the basal plasma membrane
-LM display pale blue cells with a "frothy" appearance (with hematoxylin & eosin)
-EM display apical region of cell that contains large # of mucinogen granules
-organelles of the cell (Golgi, RER, mitochondria) are located between the granules and nucleus

Front 67

Serous Demilune cells of the sublingual gland are located :

Back 67

Peripheral to the mucous acini
-deliver their secretions into their spaces between the neighboring mucus-producing cells

Front 68

Ducts of the sublingual gland:

Back 68

short intercalated and striated ducts are present, but are in number

Front 69

What gland is this?

Back 69

Sublingual gland
stained with H&E

Front 70

Classification of Submandibular (=Submaxillary) gland:

Back 70

Mixed, compound (branched) tubuloacinar gland
*Serous cells predominant

Front 71

What are the differences between submandibular and sublingual glands?

Back 71

The submandibular gland is mostly serous.
The sublingual glands are mostly mucous.

Front 72

Acini of submandibular gland is composed of:

Back 72

-mostly serous acini
-has groups of mucous acini with serous demilunes (10%)
-secretory portions contain both mucous and serous cells

Front 73

Identify each type of ducts

Back 73

Front 74

What type of gland is this?

Back 74

Submandibular/submaxillary gland

Front 75

Ducts of the submandibular glands:

Back 75

-intercalated ducts are short
-striated ducts are long and clearly evident
*striated ducts lined by cuboid cells with basal infoldings, containing mitochondria

Front 76

Major salivary products of the sublingual gland are:

Back 76

mucus
serous demilunes secrete amylase & lysozyme

Front 77

Salivary products of the submandibular gland are:

Back 77

alpha-amylase
proline-rich proteins
serous cells secrete enzymes (lysozyme)
*lysozyme imp. in hydrolyzing the walls in many types of bacteria

Front 78

Salivary products of the parotid gland are:

Back 78

serous cells contain secretory granules with abundant alpha amylase and proline-rich proteins

Front 79

Average daily production of saliva is:

Back 79

1.0 - 1.2 liters

Front 80

Function of the saliva include:

Back 80

1. protects the oral cavity by lubrication, control of bacterial flora (by presence of lysozyme, lactoferrin, and IgA), and its cleansing action
2. assists in taste sensation
3. initiates digestion of carbohydrates via action of its enzyme, salivary amylase

Front 81

Primary secretion of the saliva is by:

Back 81

Acini
-resembles extracellular fluid prior to modification by the system of ducts

Front 82

Final secretion of the saliva is by:

Back 82

a. Intercalated ducts --> may deliver bicarbonate ions into the saliva
b. Striated ducts (via their sodium pump) --> remove Na+ and Cl- ions from luminal fluid and actively pump potassium ions into it

Front 83

Saliva is a (hypertonic/hypotonic/isotonic) solution?

Back 83

HYPOtonic!

Front 84

Exocrine function of the pancreas is served by:

Back 84

acinar cells --> secrete digestive enzymes
centroacinar cells
intercalated ducts

Front 85

Endocrine portion of the Pancreas is composed of:

Back 85

Islets of Langerhans

Front 86

What type of gland is Pancreas ?

Back 86

Retroperitoneal gland
- produces both exocrine & endocrine secretions
a. exocrine - serous acinus
b. endocrine - islet of Langerhans

Front 87

Pancreas is subdivided into what regions?

Back 87

head
uncinate process
neck
body
tail

Front 88

Which region of the pancreas contains the highest concentration of enocrine tissue (islets of Langerhans)?

Back 88

Tail region

Front 89

What type of gland is this?

Back 89

Pancreas
*acini contain secretory cells with basophilic cytoplasm
- different types of endocrine cells are seen in the islet

Front 90

Capsule of the pancreas is composed of:

Back 90

- Delicate connective tissue --> subdivides the gland into lobules by forming numerous septa
- Septa convey blood and lymph vessels, nerves, and ducts in and out of the gland

Front 91

Classification of the exocrine pancreas:

Back 91

Pure serous, compound tubuloalveolar gland

Front 92

Acini of the exocrine pancreas contain:

Back 92

Only serous
centers contain centroacinar cells --> form the beginning of the duct system in the pancreas

Front 93

Shape & structure of the Acinar cells:

Back 93

-Pyramidal in shape
-round nucleus that is basally located
-Apical region densely packed with secretory granules (zymogen granules)
-RER at their base
--> strongly basophilic basal region
-intercalated duct cells known as centroacinar cells partly penetrates the acini
-NO myoepithelial cells !

Front 94

Intercellular canaliculi...

Back 94

lead from between acinar cells to the lumen of the acinus

Front 95

What type of cell is this?

Back 95

Acinar cell of the pancreas
(N) - nucleus
(G) - golgi
(C) - condensing vacuoles
(S) - mature secretory (zymogen) granules
(L) - lumen --> contains proteins recently released from the cell by exocytosis
*Acinar cells are pyramidal in shape with round nucleus that is basally located

Front 96

What type of organelles can you find within in Acinar cell under EM?

Back 96

-abundant RER
-extensive golgi apparatus
-numerous mitochondria
-many free ribosomes
*highly active cell

Front 97

Structure and appearance of the secretory granules?

Back 97

- All membrane bound
- occasionally in the process of being released in "chains" that extend to the lumen of the acinus

Front 98

Are there any myoepithelial cells in the pancreas?

Back 98

NO!
(difference between parotid glands and pancreas)

Front 99

Ducts of the acini (in pancreas):

Back 99

Extend from within the acini
No striated duct!

Front 100

Shape of the centroacinar cells:

Back 100

Low cuboidal
- constitute the initial part of the intercalated duct

Front 101

What is this slide of?

Back 101

This slide is showing an excurrent duct (D), and the main pancreatic duct (PD)
- Septums dividing the glands

Front 102

What type of cells/duct is seen here?

Back 102

Pancreas (*Islet)

Front 103

What is this slide of?

Back 103

Pancreas
-cells are packed with dense granules
pale area = centroacinar cells surrounding the acinar cells
*note: intercalated ducts

Front 104

Identify centroacinar cell.

Back 104

Pale-stained nucleus (arrow) = centroacinar cell
Darkly stained Round nucleus = acinar cells
packed with zymogen granules (pink tiny dots)

Front 105

Back 105

note: intertubular ducts on lower left corner
abundant amount of zymogen granules within the acinar cells

Front 106

Intercalated ducts lead into ...

Back 106

intercalated ducts lead into small number of inTRAlobular ducts, which then empty into the large inTERlobular ducts
* No striated ducts in pancreatic glands (difference from parotid gland)

Front 107

What type of acini are present in the exocrine pancreas?

Back 107

ONLY serous acini

Front 108

A unique feature of the pancreatic acinus is the presence of...

Back 108

Centroacinar cells (squamous-to-cuboidal epithelial) = starting point of exocrine pancreas
*Striated ducts and Myoepithelial cells are NOT present in exocrine pancreatic glands

Front 109

Where are the interlobular ducts located?

Back 109

between lobules in extensive CT and empty into the main (or accessory) pancreatic duct

Front 110

Pancreatic duct:

Back 110

the main pancreatic duct delivers pancreatic secretions into the duodenum at the papilla of Vater
*Papilla of Vater = junction between the embryological foregut & midgut

Front 111

What controls the release of pancreatic secretions?

Back 111

By 2 hormones that are released by APUD (Amine Precursor Uptake Decarboxylase) cells of the digestive tract
*hormones are secreted by the DUODENUM:
1. Cholecystokinin (pancreozymin)
2. Secretin

Front 112

Cholecystokinin (pancreozymin):

Back 112

induces the acinar cells to release pancreatic juices rich in digestive enzymes

Front 113

Digestive enzymes of the pancreatic juice released by the acinar cells are:

Back 113

Trypsin
Chymotrypsin
Peptidase
Pancreatic amylase
Lipase
Ribo-nuclease
Deoxyribonuclease

Front 114

Secretin:

Back 114

induces the intercalated ducts to secrete large quantities of an enzyme-poor, alkaline fluid that probably functions in neutralizing the acidic chyme that enters the duodenum

Front 115

Endocrine Pancreas:

Back 115

= Islets of Langerhans

Front 116

Shape & structure of Islets of Langerhans:

Back 116

-spherical clumps of richly vascularized endocrine cells
-lie scattered in random fashion among acini of the exocrine pancreas
*more numerous in the tail region
-composed of several cell types with different functions

Front 117

What are the structures circled in red?

Back 117

Islets of Langerhans (endocrine area in Pancreas)
-cells are indistinguishable in regular stain but can be differentiated by the use of special stains

Front 118

Structure and location of the Alpha cells:

Back 118

-preferentially positioned at the islet's periphery
-under EM: spherical, membrane-bound, electron-dense granules

Front 119

What type of cells constitute the majority and occupy mostly the center of each islet?
Importance of this type of cells?

Back 119

Beta cells
*produce hormone insulin --> lower blood glucose level

Front 120

Characteristics of the granules of the Beta cells:

Back 120

-membrane bound
-smaller than those of alpha cells
-characterized by presence of an irregular dense core, surrounded by an electron-lucent periphery

Front 121

Delta1 Cells:

Back 121

-less common than alpha- / beta- cells
-recognized in the EM by their relatively large, electron-lucent granules
-membranes of granules are not well defined

Front 122

Delta1 cells produce:

Back 122

Somatostatin
-depresses all the actions
-hormone that controls the release of insulin and glucagon --> reduces vol. of alkaline-rich pancreatic juices

Front 123

Other cell types include:

Back 123

C,E,G,PP cells

Front 124

Each cell type produces a specific hormone, Alpha and Beta cells produce...

Back 124

Alpha cells --> glucagon: ELEVATES blood glucose levels
Beta cells --> insulin: LOWERS blood glucose levels

Front 125

C cells are:

Back 125

represent immature / degranulated islet cells

Front 126

PP cells release:

Back 126

Pancreatic polypeptide
- controls both exocrine and edocrine cells
- hormone that may act to reduce the release of both enzyme-rich and alkaline-rich pancreatic secretions

Front 127

G cells release:

Back 127

Gastrin
- hormone that functions in modulating the release of HCL by the parietal cells of the stomach