Prac 8 - Gastrointestinal Tract

Question 1

The lip displays a mucosal covering typical of the mouth

Answer 1

stratified squamous non-keratizing epithelium

Question 2

Lip mucosal covering abrupt transformation into skin

Answer 2

stratified squamous keratized epithelium

Question 3

The epithelial lining sits on a connective tissue layer containing what

Answer 3

(submucosa)

containing collagen and elastic fibres

Question 4

The deeper layers of the mouth often contain what

Answer 4

glands and skeletal muscle fibres that help to change the shape of the oral cavity.

Question 5

What lies in the submucosa and what does this do

Answer 5

Many small blood vessels lie in the submucosa and fluid from these helps to keep the epithelium moist.

Question 6

There is an abrupt transition to what at the margin of the lips

Answer 6

stratified squamous keratinising epithelium

Question 7

The tongue is covered by a

Answer 7

stratified squamous epithelium that remains non-keratinized on its ventral surface but is often heavily keratinized on its dorsal surface due to constant abrasion of this surface.

Question 8

What is inside the tongue and where do these insert

Answer 8

Inside, it contains coarse bundles of skeletal muscle that run in different directions.
Some of these insert onto the lower jaw (extrinsic fibres) while others attach only to the fibrous connective tissue underlying the mucosa (intrinsic fibres).

Question 9

What else is embedded within the tongue

Answer 9

Many mixed sero-mucous salivary glands are embedded within the tongue.
So too are lymph nodules, particularly in the posterior third of the tongue (e.g. lingual tonsils).

Question 10

The dorsum of the tongue is thrown into complex folds known as

Answer 10

papillae

Question 11

The most common type of papillae look like what and cover where

Answer 11

Tall, pointed filiform papillae are the most common and cover the whole of the anterior two thirds of the tongue, producing a rasp-like surface.

Question 12

What kind of papillae are found at the tip and sides of the tongue.

Answer 12

Less numerous mushroom shaped fungiform papillae

Question 13

Pale-staining taste buds are embedded in the epithelium where

Answer 13

on the lateral sides of these papillae.

Question 14

How is the anterior two thirds and the posterior third on the tongue’s surface separated

Answer 14

A V-shaped row of dome-shaped circumvallate papillae separate the anterior two thirds and the posterior third on the tongue’s surface. These too bear taste buds.

Question 15

What do the Parotid Salivary Glands do

Answer 15

These glands produce a watery enzyme-rich secretion (serous secretion) rich in alpha amylase that digests starch.

Question 16

Where do the parotid salivary glands lie and how do they enter the mouth

Answer 16

They lie anterior to the ear (“para-otid”) on both sides of the face and enter the mouth via ducts adjacent to the first upper molar teeth.

Question 17

Branches of the facial nerve pass through the gland but do not innervate it. Large lymph nodes are also embedded within the glands. what gland is this

Answer 17

Parotid Salivary Glands

Question 18

The secretory cells are all of the same type in the parotid salivary glands :

Answer 18

a wholly serous gland

Question 19

how are the secretory cells arranged in the parotid gland

Answer 19

They are arranged in spherical clumps called acini (singular, acinus) that resemble bunches of grapes, the stalks representing the duct system of the gland

Question 20

What shape are the secretory cells of the parotid

Answer 20

The secretory cells are pyramidal in shape with a spherical nucleus. They show characteristics typical of protein secreting cells. The basal cytoplasm is filled with rough endoplasmic reticulum and the apex of the cell contains prominent secretion granules.

Question 21

The acini of the parotid drain into ducts lined by a

Answer 21

simple cuboidal epithelium that may become stratified at its distal end.

Question 22

Where do the Sublingual Salivary Glands lie and how do they work

Answer 22

These glands lie beneath the tongue and discharge their secretions into the floor of the mouth by a series of ducts either side of the frenulum of the tongue.

Question 23

what is the Sublingual Salivary Glands purpose

Answer 23

They are branched tubular-acinar glands that produce a sticky mucus-rich secretion that helps to lubricate the mouth and the bolus of food.

Question 24

How do the secretory cells of the sublingual gland appear

Answer 24

The secretory cells appear swollen and are filled with pale staining mucus granules. The oval nucleus is squashed to the base of the cell.

Question 25

Secretion from sublingual glands drains into ducts lined by a

Answer 25

simple or stratified cuboidal epithelium whose cells appear pinker than the secretory cells.

Question 26

Where do the Submandibular Salivary Glands lie

Answer 26

These well-defined globular glands lie subcutaneously, below the mandible, either side of the tongue. Their superficial part can be palpated easily below the lower jaw.

Question 27

How do the submandibular glands discharge

Answer 27

They discharge by a pair of ducts on to the frenulum of the tongue.

Question 28

How are the secretory cells of the submandibular gland arranged and what do they produce

Answer 28

The glands are of a branched tubulo-acinar type which are often intersperse by fat. They produce a mixed secretion, part mucus and part an enzyme-rich secretion

Question 29

How do the submandibular glands appear and why

Answer 29

The glands are of a branched tubulo-acinar type which are often intersperse by fat. They produce a mixed secretion, part mucus and part an enzyme-rich secretion because
They produce a mixed secretion, part mucus and part an enzyme-rich secretion.

The serous cells form acini or lie at the closed ends of the tubules where they form characteristic crescent-shaped “demi-lunes” (half moons).

Question 30

ike the parotid, this gland is a major source of what

Answer 30

epidermal growth factor that promotes the growth of the epithelium of the GI tract.

Question 31

The epiglottis lies where and forms a barrier between what

Answer 31

The epiglottis lies posterior to the tongue and is directly attached to it. It forms the boundary between the oropharynx and the laryngeal pharynx.

Question 32

Most of the surface of the epiglottis is covered by

Answer 32

a stratified squamous epithelium, although the lower part of its posterior (lower) surface has a pseudostratified columnar ciliated epithelium (respiratory epithelium).

Question 33

What does the epiglottis internally contain

Answer 33

Internally it contains a plate of elastic cartilage and its submucosa often contains lymph nodules and salivary glands.

Question 34

The gastro-intestinal tract has four layers:

Answer 34

• an innermost mucosa
• an underlying submucosa
• an external muscle coat (muscularis propria - sometimes referred to as the muscularis externa)
• a serosa (in some regions)

Question 35

The mucosa of the GI tract has three components:

Answer 35

a lining epithelium that is often thrown into folds,
a layer of connective tissue (lamina propria) that often contains lymphoid tissue and a ring of smooth muscle (muscularis mucosa).

Question 36

The submucosa is composed of

Answer 36

loose connective tissue that may contain glands and lymphoid tissue.any of the blood vessels that supply the gut run it this layer.
A rich plexus of nerves that is part of the enteric nervous system (Meissner’s plexus) is also present in this layer.

Question 37

The muscularis propria normally consists of two layers of smooth muscle whose contractions help to

Answer 37

break up the food and to propel it along the alimentary tract.

Question 38

Sandwiched between the layers of the muscular propria

Answer 38

are nerves that are also part of the enteric nervous plexus (Auerbach’s plexus).

Question 39

A serosal layer consisting of a what covers where

Answer 39

simple squamous epithelium covers the outside surface of those parts of the gut tube that face the peritoneal cavity.

Question 40

The oesophagus is mostly lined by a

Answer 40

stratified squamous non-keratinized epithelium.

Question 41

What is underneath the stratified squamous non-keratinized epithelium of the oesophagus

Answer 41

Underneath this is a thin lamina propria and a narrow muscularis mucosa of smooth muscle.

Question 42

Below the thoracic diaphragm the epithelium is often transformed into a

Answer 42

simple columnar type similar to that which lines the cardiac region of the stomach. This region of the oesophagus can become the site of pathological change.

Question 43

The submucosa contains many sero-mucous glands whose secretions help to

Answer 43

lubricate the oesophagus

Question 44

At the distal end of the oesophagus the submucosal layer contains many

Answer 44

large, thin-walled veins. These may become the site of oesophageal varicosities.

Question 45

At the proximal end of the oesophagus the outermost layer of muscle (muscularis externa) is composed mainly of

Answer 45

skeletal muscle but at the distal end it is composed mostly of smooth muscle.

Question 46

The stomach can be divided into 5 regions:

Answer 46

1. the cardia
2. the fundus
3. the body
4. Antrum
5. the pyloric

Question 47

What parts of the stomach show histological similarity

Answer 47

The fundus and body show very similar histological structure particularly with respects to their gastric glands. The cardia and pylorus have a different histological appearance.

Question 48

Throughout the stomach the mucosa is thrown into visible longitudinal folds known as

Answer 48

rugae.

Question 49

The stomach is lined by a

Answer 49

simple columnar epithelium punctuated by gastric pits into which the gastric glands drain.

Question 50

The muscular coat (muscularis propria) is three layers thick. Compared with the rest of the gut tube it has what

Answer 50

an additional oblique layer of fibres closest to the mucosa that helps to churn up the food within the stomach.

Question 51

The mucosa of the stomach contains many tubular glands within its mucosa. What do these do

Answer 51

These fill the lamina propria and discharge their secretions into gastric pits that communicate with the lumen of the stomach.

Question 52

There are three main types of cell within the glands of the fundus and body of the stomach,

Answer 52

(i) mucous neck cells that provide a lubricatory, acid-resistant mucus,
(ii) parietal cells that secrete HCl and intrinsic factor and (iii) chief cells that produce digestive enzymes, notably pepsin (which is secreted in an inactive form - pepsinogen).

Question 53

Full gastric glands are present in the wall of the body and fundus of the stomach. Glands of the cardia and pylorus also have gastric glands but

Answer 53

they are devoid of parietal and chief cells. The remaining mucous neck cells provide protective and lubricatory secretions.

Question 54

The stomach is lined by

Answer 54

simple columnar epithelium

Question 55

What do the cells lining stomach do

Answer 55

These tall cells produce a special acid-resistant mucin that protects the lining of the stomach.

Question 56

The surface epithelium also has deep invaginations called

Answer 56

gastric pits

Question 57

The surface epithelium also has deep invaginations called gastric pits, (openings shown by green arrows) at the bottoms of which are … what do these do

Answer 57

gastric glands. Several tall straight or branched glands open into each gastric pit. The glands contain different types of secretory cell. These glands fill the lamina propria.

Question 58

The submucosa consists of

Answer 58

loose connective tissue often with prominent blood vessels.

Question 59

The muscularis propria consists of thick bands of

Answer 59

smooth muscle often subdivided into three layers.

Question 60

Parietal cells are found where in the stomach

Answer 60

in the gastric glands in the body and fundus of the stomach. They occur mostly in the upper parts of the glands, close to the gastric pits.

Question 61

Structure and appearance of parietal cells

Answer 61

The cells are globular in shape and stain bright pink with H&E. The surface of these cells is deeply invaginated to form intracellular canaliculi and the cells contain many mitochondria. These often stain darkly and give the cytoplasm a grainy appearance.

Question 62

What do the parietal cells contain and what do they do

Answer 62

The cells are rich in the enzyme carbonic anhydrase. They secrete hydrochloric acid. They are also believed to be the source of intrinsic factor essential for the absorption of vitamin B12

Question 63

What is the structure function and appearance of the chief cells

Answer 63

Chief cells are pyramidal in shape and normally occupy the deeper parts of the gastric glands. Part of their cytoplasm stains blue with H&E and the cells can be seen to contain secretion granules.
They synthesise and secrete pepsinogen (pepsin) and lipases.

Question 64

Like the acid producing cells, these enzyme-secreting chief cells are found only where

Answer 64

only in the glands in the body and fundus of the stomach and not in the glands of the cardiac or pyloric regions.

Question 65

The gastric glands of the cardiac and pyloric regions of the stomach are shorter than those of the body or fundus and appear how

Answer 65

are coiled rather than straight.

Question 66

The gastric glands of the cardiac and pyloric regions of the stomach are composed to what

Answer 66

They are composed mainly of mucous neck cells. These are similar to those seen in the glands of the body and fundus where they are confined to a narrow band at the entrance to each gland.

Question 67

Scattered among the neck cells of the pyloric region are

Answer 67

isolated cells that produce gastrin and a bombesin-like peptide.

Question 68

, throughout the whole of the gastric mucosa there are scattered pale-staining endocrine cells that produce what

Answer 68

serotonin, somatostatin and vasoactive intestinal peptide (VIP)

Question 69

What is the purpose of the neck cells and endocrine cells in the gastric mucosa

Answer 69

Together these cells play an important role in regulating the breakdown and delivery of foodstuffs to the duodenum which occurs during the digestion process.

Question 70

The lining of the intestine is thrown into circular folds that are visible with the naked eye. These are known as

Answer 70

plicae circulares

Question 71

Where are the plicae circulares most numerous and least numerous

Answer 71

in the jejunum and least numerous in the distal part of the colon.

Question 72

What is the purpose of the plicae circulares

Answer 72

They increase the surface area of the gut available for absorption.

Question 73

The surface area is the small intestine is further augmented by what

Answer 73

microscopic leaf-like or finger-like projections of the mucosa known as intestinal villi.

Question 74

The villi are covered by what

Answer 74

simple columnar epithelium with two main cell types, enterocytes (absorptive cells) and goblet cells (mucus secreting cells). These cells are short lived but are replaced by cells that originate in the crypts.

Question 75

Each villus contains in its core what, and what do they do

Answer 75

a small arteriole, a thin walled venule and a blind-ended lymphatic (lacteal).
They also contain smooth muscle cells that rhythmically shorten the villus thereby “milking” the blood and lymph from the villus. The venules and lacteals carry absorbed nutrients to the liver.

Question 76

Between the villi are straight tubular glands known as

Answer 76

crypts of Lieberkuhn.

Question 77

What is the purpose of the crypts of Lieberkuhn

Answer 77

These contain a stem cell population. Newly formed cells migrate from the crypts on to the surface of the villi and are eventually sloughed off from the tips, the whole process taking about five days.

Question 78

columnar Enterocytes are what

Answer 78

the major absorptive cell of the small (and large) bowel.

Each cell possesses about 300 short, closely packed processes known as microvilli on its apical surface.

Question 79

Arising from the outside surface of these microvilli of the enterocytes is what

Answer 79

a well-developed glycocalyx that acts as a filter and as an anchorage for exo-enzymes.

Question 80

What is absorbed through the enterocytes

Answer 80

Most nutrients are aborbed across this epithelium although water and some glucose is able to be taken up via pathways between the cells.

Question 81

The presence of high concentrations of hexose sugars within the glycocalyx means that the brush border (like the goblet cell) stains intensely by the what procedure

Answer 81

the Periodic Acid Schiff (PAS) procedure.

Question 82

How long is the duodenum

Answer 82

12 inches (30 cm long

Question 83

What is the structure of the lining of the duodenum

Answer 83

It has a relatively smooth lining with few plicae circulares.
The villi are broad leaf-like structures and the epithelium has relatively few goblet cells.

Question 84

How do scientists histologically determine whether a sample is duodenum or jejunum

Answer 84

(However, it may be worth noting that the shape of the villi is not sufficient information by itself to determine whether the tissue is from the duodenum or jejunum. Histopathologists look for the presence of Brunner’s glands to determine whether this is duodenum or jejunum.)

Question 85

The submucosa of the duodenum is filled by a mucous secreting what gland ? and what does this help to do

Answer 85

Brunner’s gland. Its alkaline secretion helps to neutralise the chyme emerging from the stomach.

Question 86

Duodenal crypts, like those of the rest of the intestine contain newly formed enterocytes and goblet cells. In the small intestine these cells migrate on to the villi. In the large intestine where there are no villi, what happens

Answer 86

the cells simply spread out over the flattened surface of the gut.

Question 87

Dividing cells in the crypts can be recognised how

Answer 87

their compact very dark staining nuclei or by sets of chromosomes if the nuclear membrane has broken down.

Question 88

At the bottom of the crypts are a population of differeniated Paneth cells. These secrete what? what does this do? How are they recognised?

Answer 88

These secrete lysozyme, an enzyme important for the breakdown of bacterial cell walls.
They play an important part in regulatiing the bacterial flora of the gut.
The cells can be recognised by their bright pink-staining cytoplasmic granules.

Question 89

How does the epithelium of the jejunum appear

Answer 89

It has close-packed plicae circulares, the villi are long and narrow and the crypts are relatively short. Many goblet cells are present within the epithelium.

Question 90

How does the submucosa of the jejunum appear

Answer 90

The submucosa is variable in thickness but is generally very loose so that the mucosa is almost detached from the muscularis externa outside it.

Question 91

Unlike the duodenum, the jejunum does not have what in its submucosa

Answer 91

Brunner’s gland in its submucosa nor does it have the large lymph nodules (Peyer’s patches) characteristic of the ileum

Question 92

What helps to distinuish the jejunum from the duodenum and the ileum

Answer 92

he jejunum does not have Brunner’s gland in its submucosa nor does it have the large lymph nodules (Peyer’s patches) characteristic of the ileum

Question 93

Where are lymph nodules present in the jejunum

Answer 93

Lymph nodules are present in the lamina propria but they do not normally penetrate into the submucosa

Question 94

what do the Lymph nodules are present in the lamina propria but they do not normally penetrate into the submucosa look like in the ileum

Answer 94

Here the plicae circulares are not as closely packed as in the jejunum and the villi are not as tall. Goblet cells increase in number towards its distal end.

Question 95

Large patches of lymphoid tissue (Peyer’s patches) are present where in the ileum

Answer 95

Large patches of lymphoid tissue (Peyer’s patches) are present in the submucosa and in places these can be seen to erupt through the muscularis mucosa into the lamina propria.

Question 96

Explain the muscularis mucosa of the ileum

Answer 96

There is no muscularis mucosa but the muscularis externa shows two layers of smooth muscle similar to the rest of the intestine. The taenea coli originate at the base of the appendix and run the whole length of the large intestine

Question 97

The colon has four segments:

Answer 97

ascending, transverse, descending and sigmoid colon
These segments together with the caecum at its proximal end and the rectum that follows it all have a similar histological appearance.

Question 98

There are no intestinal villi in the large intestine. Instead, the mucosa consists of

Answer 98

consists of close packed intestinal crypts that mainly contain enterocytes and abundant goblet cells. The lamina propria is restricted in volume due to the packed nature of the crypts but a prominent muscularis mucosa separates the mucosa from underlying tissues.

Question 99

Why is The lamina propria is restricted in volume in the large intestine

Answer 99

due to the packed nature of the crypts but a prominent muscularis mucosa separates the mucosa from underlying tissues.

Question 100

What do the The mucosa and submucosa of the colon and rectum look like

Answer 100

The mucosa and submucosa frequently have lymph nodules embedded within them, part of the GALT system of immunologic defense.

Question 101

The muscularis externa consists of what in the colon

Answer 101

The muscularis externa consists of a thickened inner circular layer of smooth muscle and an outer layer that is drawn up into three longitudinal bands (ribbons) known as taeniae coli. These brands are clearly visible in a fresh gross specimen.

Question 102

The rectum has a similar histological appearance to the colon, being lined by

Answer 102

a simple columnar epithelium.

Question 103

The anal canal, on the other hand, is lined mainly by a

Answer 103

stratified squamous epithelium that becomes keratinized at its distal end.

Question 104

The submucosa of the anus contains what

Answer 104

The submucosa contains fat and a prominent (internal) plexus of veins that may give rise to anal varicosities.

Question 105

Describe the structure of the muscularis externa

Answer 105

The smooth muscle of the mucularis externa is thickened to form the internal anal sphincter and is surrounded by striated muscle of the external anal sphincter (derived from the pelvic bowl).

Question 106

what does the peri anal skin contains what

Answer 106

The peri-anal skin contains hair follicles and modified sebaceous glands.

Question 107

Where are the circumvalate papillae?

Answer 107

The circumvallate papillae form a V-shaped line between the anterior two-thirds and posterior third of the tongue.

Question 108

Which statement concerning filiform papillae is true?

They contain taste buds for bitter taste
They contain taste buds for salty taste
The contain taste buds for sweet taste
They contain taste buds for umami
They roughen the surface of the tongue

Answer 108

They roughen the surface of the tongue

Filiform papillae are the most numerous of the papillae on the tongue, but they do not contain taste buds. Instead, they roughen the dorsal surface of the tongue, which possibly aids in mastication.
It is worth noting that although the textbook describes different tastes being localised to different parts of the tongue, this is not true.

Question 109

The submandibular gland is

Answer 109

mixed mucous/serous

mucous glands have clear cytoplasm)

Question 110

The sublingual gland, buccal and lingual glands are mostly

Answer 110

mucous glands.

Question 111

The parotid glands are

Answer 111

serous salivary gland

Question 112

How Oesophageal mucosa recognised

Answer 112

Oesophageal mucosa is recognised by the presence of a non-keratinising stratified squamous epithelium (but this is found in the mouth as well), lymphocytes in the submucosa, and mucinous glands in the submucosa that have squamous-lined ducts.

Note: Although the textbook states that the gland ducts are lined by columnar epithelium, this is wrong – it is squamous (or, at most, in places, cuboidal)

Question 113

How can you determine that a certain mucosa is from the gastric antrum

Answer 113

the long crypts that branch, lined by mucous-secreting cells, and the lack of parietal cells (which rules out body and fundus). The superficial zone of the mucosa occupies more than half the thickness in the antrum and pylorus, but about 50% in the cardia. The duodenal mucosa has a villous architecture.

Question 114

What do parietal cells secrete?

Answer 114

Gastric parietal cells secrete hydrochloric acid (the surface mucous cells secrete a bicarbonate-rich mucous) and intrinsic factor.
Intrinsic factor plays a role in the absorption of Vitamin B12, which enters via the diet (it is not secreted by parietal cells!).
Chief cells secrete pepsinogen, which is cleaved to active pepsin in the gastric lumen.

Question 115

What do Brunner’s glands secrete, where are they found and why

Answer 115

Brunner’s glands secrete an alkaline mucus that helps neutralise gastric acid. Chyme is the name given to digested food that leaves the stomach.

Question 116

How to differentiate the ileum;s mucosa from the duodenum and jejunum

Answer 116

the villous architecture and the prominent lymphoid aggregates (Peyer’s patches) in the submucosa and mucosa. These lymphoid aggregates are not present in the jejunum or duodenum. The appendix and colon do not have a villous architecture.

Question 117

Which statement about the histology of the colon is true?

Auerbach’s plexus lies in the muscularis propria
It has a prominent brush border
It is lined by a serous epithelium
The caecum has a different histology to the ascending colon
The muscularis propria has three layers

Answer 117

Auerbach’s plexus lies in the muscularis propria

Two autonomic nerve plexuses innervate the gastrointestinal tract: Meissner’s plexus lies in the submucosa, Auerbach’s plexus lies between the layers of the muscularis propria.
The colon has a double-layered muscularis propria – inner circular, outer longitudinal.
The epithelium comprises a simple columnar layer of mucus-secreting enterocytes.
The histology of the different parts of the colon is the same.
A prominent brush border is a feature of the small intestine, not the colon.

Question 118

This is colonic mucosa how can you tell this

Answer 118

the epithelial stem cells lie at the base of the crypts of Lieberkhun. You cannot tell which part of the colon it comes from, as the entire colon looks the same. The colon does have a muscularis mucosa, immediately below the lamina propria. The colon is supplied by the superior mesenteric artery and the inferior mesenteric artery. Vitamin B12 is absorbed in the terminal ileum.