Histology - Digestive Tract

Front 1

1.What is the vermillion zone of the lips?

Back 1

At the margin of the skin of the lips the skin is transparent

Front 2

1.What epithelium characterizes the oral cavity?

Back 2

Stratified squamous epithelium; lamina propria. Diffuse salivary glands.

Front 3

1.What is the difference between the hard and soft palate?

Back 3

Hard palate (epithelium, connective tissue and bone) and soft palate (epithelium, connective tissue, skeletal muscle, submucosal glands).

Front 4

1.What is the uvula?

Back 4

core of connective tissue and skeletal muscle.

Front 5

1.What is the sulcus terminalis?

Back 5

a V shaped groove, divides the tongue into anterior and posterior regions

Front 6

1.What are the lingual tonsils?

Back 6

Rounded masses of lymphatic tissue that cover the posterior region of the tongue

Front 7

1.Classify and describe the types of tongue papillae.

Back 7

Filiform: Most abundant, in the whole tongue. Slender, conical shape 2 – 3 mm in height. They do not have taste buds and can be partially keratinized.
Fungiform: More numerous toward the tip of the tongue. Mushroom-shaped. Covering epithelium is thin so they look reddish. They have some taste buds.
Circumvallate: 10 – 14 along sulcus terminalis. Surrounded by a circular furrow with several taste buds in the lateral wall. The ducts of Ebner’s glands (serous glands) drain into the deeps of the furrow to clean the taste buds.
Foliate: Leaf-like shaped on the posterolateral margins of the tongue, with taste buds in the grooves between the folds. Here also secretion from serous (unnamed) glands drains into the bottom of the trenches.

Front 8

1.What papilla is deprived of taste buds?

Back 8

Filiform

Front 9

1.What are the Ebner’s glands?

Back 9

Serous glands that drain into the furrow to clean the taste buds

Front 10

1.What are the taste buds?

Back 10

They are barrel-shaped pale bodies connected with the exterior through the taste pore and contain the taste receptor (gustatory) cells; usually associated with papillae but everywhere in the oral cavity, palate and digestive face of epiglottis.

Front 11

1.What cells make the taste buds?

Back 11

ustentacular or supporting: Arranged like the staves of a barrel. Secrete an amorphous polysaccharide material that creates a film for fixing ions.

Neuroepithelial taste cells: 10 -14 in every taste bud, between the sustentacular cells. Long microvilli (hair receptors) lying into the amorphous material.

Basal cells: Stem cells for the former two cells.

Front 12

1.What are the properly receptor cells of the taste buds?

Back 12

Neuroepithelial cells

Front 13

1.What is the life span of the taste buds?

Back 13

10 days

Front 14

1.In the taste buds, what cells come from the differentiation of the basal cells?

Back 14

Neuroepithelial taste cells and sustentacular cells

Front 15

1.What are the hard components of the teeth?

Back 15

Hard components: Enamel, dentin, cementum.

Front 16

1.What are the soft components of the teeth?

Back 16

Soft components: Pulp, periodontal membrane, gingiva.

Front 17

1.What is the calcium content of the dentin?

Back 17

calcium content ~ 80 %

Front 18

1.What are the Tome’s dentinal fibres and what relation they have with the dentinal tubules?

Back 18

Acellular but with the processes of the odontoblasts (Tome’s dentinal fibres) that penetrate the dentin lying in canals (dentinal tubules)

Front 19

1.What would happen to dentin if odontoblasts are destroyed?

Back 19

Dentin will persist

Front 20

1.What are the lines of Owen?

Back 20

Growth lines of dentin

Front 21

1.What is the calcium content of the enamel?

Back 21

(99.5 percent is calcified)

Front 22

1.What cells create the enamel?

Back 22

It is created by the action of the ameloblasts, cells that are lost during tooth eruption.

Front 23

1.What is a enamel prism?

Back 23

Structural unit (6 µm diameter) joined by the interprismatic substance. Each prism is made by a single ameloblast.

Front 24

1.What is the cementum?

Back 24

Covers the dentin of the root. It is similar to bone but without haversian systems.

Front 25

1.What are the cementocytes?

Back 25

Lower third of the tooth

Front 26

1.What is the pulp?

Back 26

At the core of the tooth. Primitive connective tissue. One arteriole, two veins, nerve and lymphatic supply.

Front 27

1.What is the periodontal ligament?

Back 27

Between alveolar bone and tooth. It works as periostium of the alveolar bone and as suspensory ligament of the tooth.

Front 28

1.What is the disposition of the Sharpey’s fibres inn the periodontal ligament?

Back 28

Sharpey’s fibres extent from the bone into the cementum. It also supports the gingiva at the neck of the tooth.

Front 29

1.What is the gingival?

Back 29

Surrounds each tooth as a collar; it is an extension of the oral mucous membrane

Front 30

1.What is the enamel cuticle and the gingival sulcus?

Back 30

Space between the surrounding tooth and the gingivia

Front 31

1.What is the epithelial attachment of Gottlieb?

Back 31

Bounds the gingival epithelium to the enamel

Front 32

1.What is the pharynx?

Back 32

Transitional space between the mouth and the respiratory and digestive systems.

Front 33

1.What epithelia are found in the pharynx?

Back 33

stratified squamous epithelium in the digestive portion and respiratory epithelium (pseudostratified ciliated with goblet cells) in the respiratory one.

Front 34

1.In the general disposition of the digestive tract, characterize the mucosa, the submucosa, the muscularis and the serosa/adventitia.

Back 34

Mucosa
Epithelium (over a basal lamina); Lamina própria; Muscularis mucosae – inner fibres circular, outer longitudinal

Submucosa
Loose connective tissue; Submucosal nerve plexus (Meissner)

Muscularis
Inner fibres circular ; outer fibres longitudinal; Between the former two: Myenteric plexus (Auerbach) + connective tissue

Serosa or adventitia
Loose connective tissue + adipose tissue; Simple squamous epithelium (mesothelium) [just for the serosa]

Front 35

1.Characterize the esophagus, emphasizing the epithelium, mucosal and submucosal glands and the muscularis peculiarities regarding the esophageal thirds.

Back 35

Mucosa
Stratified squamous epithelium
Peg-like protrusions of the lamina propria
Muscularis mucosae thick, mostly made of longitudinal fibres
In the cardias, mucosal glands (esophageal cardiac glands)

Submucosa
Coarse collagen and elastic fibres to allow distention during swallowing
Mucosal glands (esophageal glands)
Meissner plexus absent

Muscularis
Skeletal muscle in the upper third; skeletal and smooth muscle in the middle; smooth muscle in the lower third
Pharyngoesophageal & esophagogastric are functional sphincters.

Adventitia
Connective tissue continuous with the one of the mediastinum.

Front 36

1.What is the clinical importance of the lack of serosa in the esophagus?

Back 36

Makes it more vulnerable to rupture or perforation

Front 37

1.In what portion of the stomach are the typical stomach glands found?

Back 37

The fundus

Front 38

1.What are the rugae?

Back 38

Series of ridges produced by folding in the wall of the stomach

Front 39

1.What are the gastric pits?

Back 39

openings of the glands) convey the secretion into the stomach lumen.

Front 40

1.What elements make the gastric mucosa?

Back 40

Columnar epithelium + glands + lamina propria + muscularis mucosae
Thickness: from 0.3 mm in the cardias to more than 1.5 mm in the body

Front 41

1.What elements make the gastric submucosa?

Back 41

Connective tissue, vessels, nerves, adipocytes. The submucosal plexus (Meissner) innervates the submucosa, mucosa and the muscularis mucosae.

Front 42

1.What are the functions of the Meissner plexus in the stomach?

Back 42

Innervates the submucosa, mucosa and muscularis mucosae

Front 43

1.What is the disposition of the muscle layers in the stomach?

Back 43

It has a random orientation (classically described with three layers)
Longitudinal layer absent from big portions of the anterior and posterior faces
The circular layer is poorly developed in the cardiac region, but thickened at its pyloric end (sphincter)

Front 44

1.What are the functions of the Auerbach plexus in the stomach?

Back 44

Innervates the stomach muscles

Front 45

1.What are the mucous neck cells?

Back 45

Mucus-secreting cells lie just below the gastric pits; they are similar to the surface mucous cells but shorter.

Front 46

1.What are the parietal cells?

Back 46

1.Large, round, frequently binucleated acidophilic (mitochondria 30-40% of the volume), with a intracellular canalicular system that includes microvilli.

Front 47

1.What are the two main secretions of the parietal cells?

Back 47

Secrete hydrochloric acid and intrinsic factor for vitamin B12 absorption.

Front 48

1.What are the chief cells?

Back 48

Protein-secreting cells (outstanding basal basophilia due to RER). They predominate at the lower half of the gland.

Front 49

1.What are the two main secretions of the chief cells?

Back 49

Secrete pepsinogen (which is converted to pepsin) and gastric lipase (almost useless, an atavism).

Front 50

1.What are the enteroendocrine cells?

Back 50

Hormone-secreting cells (more than 20 hormones). Widely distributed in the digestive tract, the ducts of digestive glands and also in the respiratory system. They secrete into blood vessels and neighbouring tissues.

Front 51

In what other places similar cells are found? (enteroendocrine cells)

Back 51

Ducts of the digestive glands and also the respiratory system

Front 52

1.What are the systems used by the small intestine to increase the surface of absorption?

Back 52

It increases its absorptive surface in the search for efficient absorption, using: 1)
Intestinal loops; 2) Plicae circulares; 3) Interstinal villi; 4) Microvilli of enterocytes

Front 53

1.What are the plicae circulares?

Back 53

Also known as valves of Kerkring, they are folds of both mucosa and submucosa.

Front 54

1.Where are the plicae circulares found?

Back 54

They extend one half or even two thirds of the lumen, and increase the absorptive surface area by a factor of three. Being more prominent in distal duodenum and jejunum, they disappear one meter before the ileocecal valve.

Front 55

1.What are the intestinal villi?

Back 55

Fingerlike and leaflike projections, unique to the small intestine that icrease the absorptive surface area by a factor of ten. They have lamina propria as core, and there we find fenestrated capillaries and lymphatic capillaries (lacteal). The muscularis mucosae sends fibres that provide them with movement.

Front 56

1.What is a lacteal?

Back 56

Lymphatic capillaries

Front 57

1.From where do the smooth muscle fibres found in the intestinal villi come from?

Back 57

muscularis mucosae

Front 58

1.What are the intestinal crypts?

Back 58

Also known as crypts of Lieberkühn. They are mucosal tubular invaginations extended to the muscularis mucosae that open to the intestinal lumen at the base of the villi.

Front 59

1.Describe the functions and activities that happen in the intestinal crypts.

Back 59

The brush border enzymes are produced here. The replicative zone (abundant mitosis) is represented at the lower half of the crypt

Front 60

1.What are the enterocytes?

Back 60

They line the surface of the villi (that is why they are sometimes called villous absorptive cells) and crypts, and is the place for terminal digestion and absorption. They are tall columnar cells with vesicular nuclei, microvilli (~ 3000 per cell, which increase 600 times the absorptive surface), thick glycocalyx (up to 0.5 µm), junctional complexes and basal infoldings.

Front 61

1.What are the functions of the enterocytes?

Back 61

secretory functions: digestive enzymes of the glycocalyx and transport enzymes of the lateral membrane. They synthesize the chylomicrons and also have beta-galactosidase activity.

Front 62

1.What are the goblet cells?

Back 62

Goblet-shaped cells with compressed nuclei and empty appearance in HE. They increase their frequency from the proximal to the distal small intestine.

Front 63

1.What are the Paneth cells?

Back 63

At the base of the crypts of the small intestine. They have large eosinophilic granules that contain lysozyme, an arginine-rich protein, alfa-defensin and zinc. They have phagocytic abilities and also intracellular IgG and IgA. They 1) May contribute in the control of the microbial flora, 2) May phagocyte bacteria and protozoa, 3) May secrete digestive enzymes and 4) May contribute to the elimination of heavy metals (particularly zinc).

Front 64

1.Where are the Paneth cells found?

Back 64

At the base of the crypts of the small intestine.

Front 65

1.What are the functions of the Paneth cells?

Back 65

hey have phagocytic abilities and also intracellular IgG and IgA. They 1) May contribute in the control of the microbial flora, 2) May phagocyte bacteria and protozoa, 3) May secrete digestive enzymes and 4) May contribute to the elimination of heavy metals (particularly zinc).

Front 66

1.What are the microfold cells?

Back 66

Also known as M cells; epithelial antigen-presenting cells that cover large lymph nodules (i.e. Peyer patches and others) and have microfolds on their luminal surface. They provide a constant stimulation of the GALT and may act as entry points for some pathogens.

Front 67

1.What are the intermediate cells?

Back 67

These immature cells are majority at the lower half of the crypt.
The ones committed to be goblet cells, develop secretory droplets
The ones committed to become enterocytes lose those droplets and increase their amounts of organelles.

Front 68

1.What are the stem cells and what characterizes them?

Back 68

Located close to the bottom of the crypts; precursor of all the other properly intestinal cells. Highly resistant to aggression.
Division of stem cells produces one that will differentiate and other that will remain in the stem cell pool.If it will become a goblet or absorptive cell, it undergoes two divisions.
If it will become an enteroendocrine cell, it undergoes one extra division

Front 69

1.Describe the epithelial cell renewal of the intestinal villi.

Back 69

Nearly all cells migrate from the crypt to the tip of the villus (Paneth cells do not migrate). The turnover for enterocytes and goblet cells is 5 – 6 days.

Front 70

1.What histological structure characterizes the duodenum?

Back 70

Four portions. It has the Brunner glands, located in the submucosa, with mucus units. The mucin they secrete contribute to the alkalinization required by the pancreatic enzymes.

Front 71

1.What are the Brunner glands?

Back 71

Glands located in the submucuosa. The mucin they secrete contribute to the alkalinization required by the pancreatic enzymes.

Front 72

1.What is the functional importance of the jejunum?

Back 72

2.5 m in length, it is the primary site of nutrients absorption.

Front 73

1.What histological structure characterizes the ileum?

Back 73

The Peyer patches (aggregated lymph nodules)

Front 74

1.What substance is specifically absorbed in the ileum?

Back 74

vitamin B12

Front 75

1.What is the function of the colon?

Back 75

Reabsorption of water and salt for an efficient elimination of wastes

Front 76

1.What is the general structure of the appendix?

Back 76

Many lymphatic nodules occupying the lamina propria and the submucosa.
Uniform layer of longitudinal muscle in the muscularis externa.
Teniae coli of the cecum converge at the base of the appendix.

Front 77

1.Describe the colonic mucosa, including its cell content.

Back 77

Colonic mucosa
Simple columnar epithelium arranged as tubular glands.
Plicae and villi are absent.
Same cells of the small intestine (Paneth cells are rare) plus the caveolated (tuft) cell, maybe an old goblet cell. Enterocytes predominate over goblet cells (4:1 ratio) at first, but in the rectum there are in equal quantities (1:1 ratio).

Front 78

1.What are the tuft or caveolated cell?

Back 78

caveolated (tuft) cell, maybe an old goblet cell. Enterocytes predominate over goblet cells (4:1 ratio) at first, but in the rectum there are in equal quantities (1:1 ratio).

Front 79

1.What characterizes the colonic muscularis?

Back 79

The outer (longitudinal) layer creates three equally spaced thick bands: teniae coli (between the teniae, the outer layer is thin). Bundles of muscle from the teniae penetrate the inner circular layer at intervals; their contraction creates the haustra (sacculations), allowing colonic segments to contract independently.

Front 80

1.What are the haustra?

Back 80

Small pouches caused by sacculation that give the colon a segmented appearance

Front 81

1.What are the anal sinuses?

Back 81

The lower rectum is part of the anal canal and has longitudinal folds that alternate with depressions (anal sinuses).

Front 82

1.What is the anal canal?

Back 82

Extends ~ 4 cm from the rectoanal junction to the anus. The muscularis mucosae disappears at the rectoanal margin. The upper portion has rectal glands that secrete mucus; the lower has apocrine circumanal glands, hair follicles and sebaceous glands. ~ 2 cm above the anus the lining changes from simple columnar to stratified squamous epithelium (continuous with the skin).

Front 83

1.What structures contribute to the anal muscles?

Back 83

Circular layer of the muscularis externa thickens to form the internal anal sphincter. Striated muscles of the perineum form the external anal sphincter.