Histology

Question 1

The oral cavity, oropharynx and laryngopharynx is covered over by what?

Answer 1

Stratified squamous epithelium which is generally not keratinised

Question 2

The nasal cavity and nasopharynx are covered over by what?

Answer 2

Respiratory epithelium

Question 3

Describe the anterior 2/3 of the tongue

Answer 3

Stratified squamous epithelium, thin on ventral surface, thick and with papillae on the dorsal surface

Question 4

Describe the posterior 1/3 of the tongue

Answer 4

Covered by smooth stratified squamous epithelium which, except for the circumvallate papillae, lacks papillae but does have substantial lymphoid aggregates in the submucosa

Question 5

What are the four types of papillae on the tongue?

Answer 5

• fungiform
• circumvallate
• foliate
• filiform (no tastebuds, occupy much of dorsal surface)

Question 6

Describe the entrance to the oropharynx

Answer 6

The pharynx includes a ring of lymphoid tissue composed of the palatine tonsils, lingual tonsils, tubal tonsils and pharyngeal tonsils (adenoids)

Question 7

Name the 4 major layers of the digestive tract

Answer 7

• mucosa
• submucosa
• muscularis externa
• serosa or adventitia

Question 8

Describe the three layers of the mucosa

Answer 8

• epithelium; sits on a basal lamina
• lamina propria; loose connective tissue
• muscularis mucosae; thin layer of smooth muscle

Question 9

Describe the submucosa

Answer 9

Loose connective tissue

Question 10

Describe the muscularis externa

Answer 10

Two thick layers of smooth muscle, an inner circular layer and an outer longitudinal layer

Question 11

Describe the serosa / adventitia

Answer 11

Outer layer of connective tissue that either suspends the digestive tract or attaches it to other organs

Question 12

Describe the muscle of the oesophagus

Answer 12

Roughly the upper 1/3 is skeletal muscle and then this transition to smooth muscle as it is involve in swallowing

Question 13

Describe the gastro-oesophageal junction

Answer 13

Abrupt transition from stratified squamous epithelium of oesophagus to the simple columnar epithelium of the cardia of the stomach

Question 14

What are gastric pits?

Answer 14

Holes in the flat surface of the stomach

Question 15

What are gastric glands?

Answer 15

Found at the bottom of the gastric pits

Question 16

Describe the surface mucous cells

Answer 16

High in bicarbonate ions in the mucous, protective mucous, these will dive into the tubes

Question 17

Describe the anatomy of glands

Answer 17

• isthmus, neck and body / fundus
• where things such as pepsinogen is produced
• acid producing cells found towards the top of the gland and enzyme producing cells towards the bottom

Question 18

Gastric pits are lined by what?

Answer 18

Surface mucous cells

Question 19

Describe the cells of the gastric gland

Answer 19

• the isthmus has mostly parietal cells and stem cells
• the isthmus has mostly parietal cells and stem cells
• the neck is mostly neck mucous cells and parietal cells
• the fundus (base) is mostly chief cells, with a few parietal cells and enteroendocrinecells

Question 20

What are chief cells?

Answer 20

Digestive enzyme secreting cell

Question 21

What are parietal cells?

Answer 21

Hydrochloric acid producing cells, deep invaginations in the cytoplasm, microvilli, large surface area, loads of mitochondria, energy dependent cells

Question 22

Name the different regions of the stomach

Answer 22

• cardia
• body
• pylorus

Question 23

Describe the cardia of the stomach

Answer 23

Deep gastric pits that branch into loosely packed, tortuous glands

Question 24

Describe the body of the stomach

Answer 24

Shallow gastric pits with long straight gastric glands

Question 25

Describe the pylorus of the stomach

Answer 25

Deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia

Question 26

What layer aids the churning action of the stomach?

Answer 26

Muscularis externa

Question 27

Describe the gastroduodenal junction

Answer 27

There is an abrupt transition from stomach mucosa to duodenal mucosa. The inner, circular layer of smooth muscle is markedly thickened to form the pyloric sphincter

Question 28

What are the crypts of lieberkuhn?

Answer 28

Between the bases of adjacent villi are pits ‘drilling’ downward

Question 29

Name the three sections of the small intestine

Answer 29

• duodenum
• jejunum
• ileum

Question 30

Describe the duodenum

Answer 30

Contains brunner glands in the submucosa

Question 31

Describe the jejunum

Answer 31

Tallest villi, located on permanent circular folds of the mucosa and the submucosa, the pilcae circularis. Lymphoid follicles infrequent

Question 32

Describe the ileum

Answer 32

Characterised by shorter villi and aggregations of lymphoid follicles called peyers patched found in the submucosa and often extending into the lamina propria

Question 33

What are the only structure with glands in the submucosa?

Answer 33

Oesophagus and duodenum

Question 34

Describe enterocytes

Answer 34

The most numerous cells, they are tall columnar cells with a brush border and are the principle absorptive cells

Question 35

Describe goblet cells

Answer 35

Produce mucin to protect epithelium and lubricate passage of material

Question 36

Describe Paneth cells

Answer 36

Found at the base of the crypts of lieberkuhn, they have a defensive function and have a role in regulating bacterial flora (secrete lysozyme and definsins)

Question 37

Describe enteroendocrine (neuroendocrine) cells

Answer 37

Produce hormones that contribute to the control of secretion and motility (eg. gastrin, cholecystokinin, vasoactive intestinal peptide)

Question 38

Describe stem cells

Answer 38

Found at the base of the crypts of lieberkuhn, they divide to replenish epithelium

Question 39

Describe the duodenum

Answer 39

• the duodenum receives the acidic, partly digested semifluid material called chime from the stomach
• it differs from any other region of the GI tract below the oesophagus in that it has glands located within the submucosa
• these glands are called brunners glands
• when stimulated by the presence of chime they produce a thin, alkaline mucous to neutralise the chime

Question 40

Describe the ileum

Answer 40

There is a substantial amount of lymphoid tissue associated with the gut. Much of this consists of scattered lymphocytes, but areas of relatively large aggregations of lymphoid tissue exist, particularly in the ileum. These are called peyers patches

Question 41

Describe the absorptive cells of the large intestinal epithelium

Answer 41

For removal of salts and thereby water

Question 42

Describe goblet cells of the large intestinal epithelium

Answer 42

For secretion of mucus to lubricate the colon

Question 43

What is teniae coli?

Answer 43

In the large intestine, the outer longitudinal smooth muscle is distinct. It is not continuous but is found in 3 muscular strips

Question 44

Describe the appendix

Answer 44

A blind-ending hollow extension of the cecum. The structure is similar to the rest of the colon, but the crypts are far less abundant and there is typically a circular arrangement of lymphoid tissue in the submucosa and often the lamina propria. The lymphoid tissue tends to decline with age

Question 45

Describe the rectoanal junction

Answer 45

There is a distinct junction between the mucosa of the rectum and the non-keratinised stratified squamous epithelium of the anal canal. The 2-3cm long anal canal is then continuous with the keratinised stratified squamous epithelium of the surrounding skin

Question 46

The enteric nervous system has interconnected networks of fibres has what?

Answer 46

• two plexuses
• one in the submucosa
• one between the muscle layer of the muscular externa (myenteric)