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Histology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What is the digestive system responsible for?

A

the

processing, digestion and absorption of food and the elimination of the residue

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2
Q

What occurs in the oral cavity?

A

Takes in and fragments food (mastication)

Saliva moistens and begins digestion (alpha amylase)

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3
Q

What is the general function of the esophagus?

A

conveys food to stomach by peristalsis

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4
Q

What is the general function of the stomach?

A

gastric juice begins digestion

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5
Q

What is the general function of the samll intestine?

A

absorption of nutrients begins

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6
Q

What is the general function of the large intestines?

A

i) absorption continues (especially H20)

II) feces are compacted and expelled

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7
Q

What is the general function of the accessory glands?

A

1) small glands located in the wall throughout the digestive system
2) large glands (liver, pancreas, salivary) are connected to the tube via ducts

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8
Q

What kind of epithelium is present in Masticatory Mucosa?

A

Parakeratinized stratified squamous epithelium

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9
Q

What is stratified squamous?

A

multilayered epithelium with flattened superficial cells

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10
Q

What is parakeratinized?

A

A moist keratin layer that is still living

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11
Q

What is the epithelial/CT interface like in the masticatory mucosa?

A

Tall rete pegs and Connective Tissue Papillae

Unerlying CT is fairly immovable and not extensively vascularized

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12
Q

Where is it located and why?

A

Located in areas subject to wear and tear
(gums and hard palate)
Superficial cells are tightly compacted to facilitate abrasion resistance

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13
Q

What kind of epithelium is present in the lining mucosa?

A

Nonkeratinized stratified squamous epithelium

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14
Q

What is the epithelial/CT interface like in the lining mucosa?

A

1) shallow rete pegs and CT papillae

2) underlying CT is fairly movable and more extensively vasularized

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15
Q

Where is it located and why?

A

lips, cheeks, soft palate

floor of mouth and inferior surface of the tongue

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16
Q

What epithelium is the outer surface of the lips and cheeks covered by?

A

Orthokeratinized stratified squamous epithelium

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17
Q

What epithelium is the inner surface of the lips and cheeks covered by?

A

lining mucosa (nonkeratinized stratified squamous epithelium

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18
Q

What is the vermilion of the lips and cheeks?

A

pink transition zone between the external and internal surfaces

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19
Q

What muscle is located in the lips?

A

Orbicularis oris muscle - skeletal muscle in the lip

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20
Q

What muscle is located in the cheeks?

A

Buccinator muscle - skeletal muscle in the cheek

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21
Q

What is the general composition of the tongue?

A

largely a mass of interlacing bundles of skeletal muscle fibers and CT

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22
Q

What is the general composition of the extrinsic muscles of the tongue?

A

extrinsic muscles have an attachment point outside of the tongue that function to move the tongue in different directions

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23
Q

What is the general composition of the intrinsic muscles of the tongue?

A

intrinsic muscles are contained entirely within the tongue that function to change the shape of the tongue

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24
Q

What functional activities does the tongue participate in?

A

1) manipulate food during mastication
2) essential for production of many sounds during speech
3) move fragmented food toward pharynx to initiate swallowing

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25
Q

What does the presence of intrinsic and extrinsic muscles permit the tongue to do?

A

Permits the tongue to have complex movements that move in many different planes

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26
Q

What is the sulcus terminalis of the tongue and where is it??

A

1) superior shallow groove delineating the anterior and posterior regions on tongue

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27
Q

What is the foramen cecum and where is it?

A

thyroid gland origin that is at the midline of the sulcus terminalis

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28
Q

Where is the Pharyngeal Region of the Tongue located?

A

posterior third of tongue (root oriented vertically in the pharynx)

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29
Q

How is the Pharyngeal Region of the Tongue oriented?

A

root oriented vertically in the pharynx

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30
Q

What structures are located in the Pharyngeal Region of the Tongue?

A

covered by lingual tonsils

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31
Q

What are tonsils?

A

aggregates of lymphoid nodules

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32
Q

Where is the Palatine Region of the Tongue located?

A

anterior two thirds of tongue

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33
Q

How is the Palatine Region of the Tongue oriented?

A

body oriented horizontally in oral cavity

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34
Q

What structures are located in the Palatine Region of the Tongue ?

A

covered by specialized mucosa containing lingual papillae

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35
Q

What are lingual papillae?

A

small, bumpy, hair like structures on the dorsum of the tongue, giving it a rough texture

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36
Q

What are the different types of lingual papillae?

A

Filiform papillae
Fungiform papillae
Vallate (Circumvallate) papillae
Foliate papillae

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37
Q

How common are Filiform Papillae?

A

Most prevalent

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38
Q

What do Filiform Papillae look like?

A

conical shaped and covered with a keratinized stratified squamous epithelium

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39
Q

Where are Filiform Papillae found?

A

evenly distributed over the anterior portion of the tongue

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40
Q

What are Filiform Papillae used for?

A

contain afferent nerve endings sensitive to touch

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41
Q

Any taste buds located on Filiform Papillae?

A

no

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42
Q

How common are Fungiform Papillae?

A

Relatively common

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43
Q

Where can Fungiform Papillae be found?

A

scattered randomly among the filiform papillae

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44
Q

What do Fungiform Papillae look like?

A

mushroom shaped and about as tall as filiform papillae

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45
Q

Any taste buds located on Fungiform Papillae?

A

contain taste buds on the superior surface

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46
Q

How common are Vallate Papillae?

A

largest in size; fewest in number

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47
Q

Where are Vallate Papillae found?

A

8-12 located just anterior to sulcus terminalis

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48
Q

What do Vallate Papillae look like?

A

1) large mushroom shaped papillae recessed into tongue mucosa
2) surrounded by a deep circular groove (moat)

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49
Q

Any taste buds located on Vallate Papillae ?

A

taste buds present on the lateral sides of these papillae (facing the moat)

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50
Q

How common are Foliate Papillae?

A

sometimes difficult to see in adult humans

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51
Q

Where are foliate papillae found and what do they look like?

A

parallel ridges on the lateral edges of the tongue

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52
Q

Any taste buds located on foliate papillae?

A

contain many taste buds on the sides of these ridges

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53
Q

What are von Ebner’s Glands and where are they located?

A

small salivary glands intrinsic in the tongue

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54
Q

What do von Ebner’s Glands do and why is it necessary?

A

flush out taste buds on circumvallate and foliate papillae for sequential tasting, cleaning mechanism

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55
Q

Where are Taste Buds located?

A

present on fungiform, vallate and foliate papillae

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56
Q

What is the general structure of taste buds?

A

barrel shaped with a taste pore

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57
Q

What cell types are present in a taste bud?

A

Taste receptor cell
Sustentacular cell
Basal cell

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58
Q

What do sustentacular cells do?

A

Provide structure to the taste bud

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59
Q

What do basal cells do?

A

renew sustentacular and taste receptor cells

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60
Q

How are tastes perceived?

A

flavor is perceived as various combinations of four basic tastes:
* sweet, sour, bitter, salt

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61
Q

What and where are the minor salivary glands?

A

lingual, labial, buccal and palatine

located in many areas of the oral cavity

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62
Q

What are the minor salivary glands’ functional responsibility?

A

secrete saliva more or less continuously to moisten the oral cavity

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63
Q

What is a compound exocrine gland?

A

An exocrine gland with many branches and a duct

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64
Q

What are the three major salivary glands?

A

parotid, submandibular and sublingual

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65
Q

When do the major salivary glands secrete saliva?

A

secrete saliva intermittently in response to food related stimuli

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66
Q

What is the general composition of saliva?

A

mixed secretion of mucous and serous secretions (i.e., enzymes)

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67
Q

About how much saliva is produced each day?

A

about a liter/day of saliva is produced; 90% of it is water

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68
Q

What are the functions of saliva?

A

 moisten the oral mucosa
 moisten ingested food (facilitating tasting and swallowing)
 begin digesting carbohydrates ( amylase)
 buffers the contents of the oral cavity
 contains antibodies and lysozyme for antibacterial protection

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69
Q

Where is the parotid gland located?

A

subcutaneously anteroinferior to each ear (often contains large amounts of adipose)

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70
Q

Where does the parotid duct enter oral cavity?

A

Upper second molar

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71
Q

What kind of secretions are produced in the parotid gland?

A

Entirely serous secretion

- watery secretion often containing enzymes

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72
Q

What is the histological appearance when the parotid gland is stained with H&E?

A

typically stains purple

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73
Q

Where is the submandibular gland located?

A

bilaterally along the medial surface of the body of the mandible

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74
Q

Where does the Wharton’s duct enter oral cavity?

A

duct opens onto floor of oral cavity posterior to the lower incisor teeth

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75
Q

What kind of secretions are produced in the submandibular gland?

A

mixed secretion which is mostly serous

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76
Q

What is mucous?

A

mucous is a thick viscous secretion containing glycoprotein

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77
Q

What is the histological appearance of mucous when stained with H&E?

A

typically pale staining

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78
Q

What are serous demilunes?

A

Mucous cells covered with serous demilunes around the edge

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79
Q

Where are sublingual glands located?

A

bilaterally under tongue, beneath the mucosal lining of the floor of the oral cavity

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80
Q

Where does the sublingual duct enter oral cavity?

A

multiple ducts open near the submandibular ducts

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81
Q

What kind of secretions are produced?

A

mixed secretion which is mostly mucous

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82
Q

What is the histological appearance when stained with H&E?

A

Light and pale staining

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83
Q

What is the hard palate?

A

1) Anterior 2/3 of oral cavity roof
bony and covered by masticatory mucosa
2) able to withstand the abrasive activities associated with mastication

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84
Q

What kind of mucosa is in the hard palate?

A

masticatory mucosa

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85
Q

What is the soft palate?

A

Posterior 1/3 of oral cavity caivty

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86
Q

What kind of mucosa is on the soft palate?

A

Lining mucosa

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87
Q

What is the uvula?

A

1) raises and pushes against posterior pharyngeal wall during swallowing

located posteroinferiorly

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88
Q

What happens when swallowing?

A

raises and pushes against posterior pharyngeal wall during swallowing

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89
Q

Where are palatine tonsils?

A

situated bilaterally in the tonsillar fossae

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90
Q

What are palatine tonsils?

A

paired masses of lymphoid tissue

- most suseptible to chronic inflammation and subject to tonsillectomy

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91
Q

What is the pharynx?

A

1) located at the back of the mouth

2) serves both as a digestive passageway and as a respiratory airway

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92
Q

Where is the oropharynx?

A

between the soft palate and larynx

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93
Q

What is type of mucosal lining is found in the oropharynx and laryngopharynx?

A

Lining mucosa (nonkeratinized stratified squamous epithelium)

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94
Q

Where is the nasopharynx?

A

above the soft palate

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95
Q

What is respiratory epithelium?

A

pseudostratified columnar epithelium with cilia and goblet cells

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96
Q

What is pseudostratified?

A

Falsely layered as it is only one layer but appears to be multilayered but each cell touches basement membrane

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97
Q

What are goblet cells?

A

Cells that produce mucous

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98
Q

What are cilia?

A

Cilia are hairlike structures

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99
Q

Where is the pharyngeal tonsil?

A

1) single midline structure on posterior wall of pharynx

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100
Q

What is the pharyngeal tonsil also known as?

A

adenoids

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101
Q

What problems arise with swollen adenoids?

A

when enlarged it may obstruct the nasopharynx

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102
Q

What are tonsils?

A

aggregates of unencapsulated lymphoid nodules

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103
Q

What are lymphoid nodules?

A

rounded, dense accumulations of lymphocytes (primarily B lymphocytes)

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104
Q

Where are the tonsils located?

A

the tonsils (lingual, palatine and pharyngeal) form an incomplete ring around the entrance to the digestive and respiratory tracts

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105
Q

What advantage is there in having tonsils?

A

1) in this position, immune system cells constantly come in contact with antigens entering from the outside world
2) primes these cells to make antibodies and defend the organism

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106
Q

What 4 layers make up the lumen of the digestive tract?

A

 Mucosa
 Submucosa
 Muscularis externa
 Serosa/Adventitia

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107
Q

What do you need to remember about the lumen of the digestive tract?

A

It is functionally external to the body

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108
Q

What is the epithelial lining of the mucosa of the digestive tract?

A

type of membranous epithelium and the presence and nature of any
associated glands is dependent on location along the digestive tract

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109
Q

Function of the epithelial lining of the digestive tract?

A

1) selective barrier between luminal contents and body tissues
2) secretory for HCl, digestive enzymes and mucous
3) absorptive for metabolic substrates and H2O

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110
Q

What is the lamina propria of the digestive tract?

A

usually loose CT often rich in immune system cells (diffuse lymphatic tissue)

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111
Q

Function of the mucosa of the digestive tract?

A

1) supports membranous epithelium and accommodates small intrinsic glands
2) contains the vasculature for receiving the absorbed metabolites
3) contains the GALT (gut associated lymphatic tissue) as first line of defense

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112
Q

Where is diffuse lymphatic tissue located?

A

located deep to epithelial linings of digestive, respiratory, urinary and reproductive tracts

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113
Q

What role does diffuse lymphatic tissue play in the immune system?

A

ready to respond to entry of infectious organisms and toxins crossing these barriers

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114
Q

What do lymphoid nodules look like?

A

1) rounded, dense accumulations of lymphocytes appearing within diffuse lymphatic tissue
2) lack a connective tissue capsule so their borders are diffuse

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115
Q

Where are lymphoid nodules unencapsulated nodules found?

A

Tonsils, Peyer’s patches, Appendix

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116
Q

What does it mean to say lymphoid nodules are transient?

A

Most are temporary

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117
Q

What are tonsils and where are they located?

A

aggregates of unencapsulated lymphoid nodules in walls near the soft palate, in the nasopharynx and on the tongue

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118
Q

What are Peyer’s patches and where are they located?

A

1) large aggregates of confluent lymphoid nodules

2) situated mostly in the walls of the ileum (part of small intestine)

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119
Q

What is the function of lymphoid nodules?

A

provide immunological protection against pathogenic invasion via vulnerable exposed absorptive surfaces

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120
Q

Where is the appendix located?

A

In the lower right abdomen

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121
Q

Where are plasma cells typically found?

A

typically located just deep to the epithelial lining of the GI and respiratory tracts

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122
Q

Plasma cells are the tissue form of what circulating cell?

A

a B lymphocyte that migrated into connective tissue

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123
Q

What cells are found in the dense lymphatic tissue of lamina propria?

A

Various leukocytes including neutrophils, eosinophils and lymphocytes

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124
Q

Plasma cells are often associated with what kind of CT?

A

often associated with loose connective tissue

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125
Q

What is the shape of plasma cells?

A

typically a rounded cell with an eccentric round nucleus

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126
Q

What is the heterochromatin like in plasma cells?

A

often the nuclear heterochromatin is positioned like spokes on a wheel

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127
Q

What is a negative golgi image?

A

Does not stain purple

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128
Q

What does plasma cells do?

A

produce tissue based antibodies

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129
Q

Why is immunity safety from reinfection as opposed to infection?

A

Immunity refers to being exposed to an antigen to allow for proper protection from the same antigen therefore it is safety to reinfection

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130
Q

What is an antigen?

A

is any macromolecule (possibly on a bacterium) that is determined to be
“foreign” to the body

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131
Q

How does a plasma cell react to antigens?

A

1) plasma cell is part of a system (Immune system) which can respond to the
antigen and facilitate destruction/remova
2) plasma cell responds by synthesizing antibodies

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132
Q

What is an antibody?

A

protein produced with specificity for only one antigen

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133
Q

How does an antibody facilitate antigen removal?

A

antibody binds specifically to antigen and antigen is removed

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134
Q

Why are antibodies continually available?

A

following initial immune response antibodies are circulating and continually
available to respond to antigenic presence

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135
Q

How common are macrophages?

A

almost as common as fibroblasts in ordinary connective tissue

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136
Q

Macrophages are the tissue form of what circulating cell?

A

Monocytes

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137
Q

What is the morphology of macrophages?

A

1) large round/oval cell with eccentric bean-shaped nucleus

2) many lysosomes (primary and secondary) and probably residual bodies

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138
Q

What is the function of the macrophage?

A

1) major function is phagocytosis of infectious microorganisms, cell debris, particulate matter, old erythrocytes
2) antigen presentation in the immune system
3) many together may form foreign body giant cells

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139
Q

What is the muscularis mucosa’s typical composition?

A

two thin layers of smooth muscle (inner circular; outer longitudinal)

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140
Q

In what way does contraction in muscularis mucosa facilitate digestion and/or absorption?

A

facilitates digestion/absorption by maximizing contact between luminal contents and surrounding mucosal surfaces

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141
Q

What is the typical tissue composition of submucosa?

A

mostly dense irregular CT (with some areas of nondense CT)

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142
Q

What other kinds of structures are seen in the submucosa?

A

contains larger neurovascular elements, autonomic plexuses and lymphatic vessels

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143
Q

Does submucosa ever contain glands and/or GALT?

A

sometimes contains glands which are distinctive to certain regions of the tract

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144
Q

Mast cells are closely related to what circulating cell?

A

Basophils

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145
Q

Mast Cells are usually located near what structures?

A

typically found near blood vessels throughout body

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146
Q

What is the mast cell’s morphology?

A

highly granulated cell with cytoplasmic granules that contain heparin, histamine, chemotactic factors

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147
Q

What is heparin?

A

weak anticoagulant

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148
Q

What is histamine

A

an inflamitory agent (causes BV dilation, endothelial contraction)

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149
Q

What do chemotactic factors do?

A

chemotactic factors attract neutrophils and eosinophils

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150
Q

What is the combined effect of mast cell degranulation?

A

degranulation leads to the formation of “leaky” endothelium

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151
Q

How does degranulation facilitate immune responses?

A

promotes the infiltration of serum components into the tissue space

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152
Q

What is the typical tissue composition of muscularis externa?

A

usually two relatively thick layers of spiraling smooth muscle

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153
Q

What is the orientation of this tissue?

A
  • inner sublayer (closer to lumen) generally circular
  • outer sublayer is generally longitudinal
  • sometimes modified to form sphincters
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154
Q

What is the function of the muscularis externa layer?

A

create peristaltic contractions to mix and propel luminal contents distally

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155
Q

How is the muscularis externa activity coordinated?

A

coordinated by myenteric plexuses between the two layers

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156
Q

What is the composition of serosa?

A

loose CT, rich in adipose, blood and lymph vessels

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157
Q

What is mesothelium?

A

simple squamous epithelium

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158
Q

Where is mesothelium found in serosa?

A

1) mesothelium covering underlying CT

2) seen on organs that are suspended in the peritoneal cavity

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159
Q

What is the difference between serosa and adventitia?

A

Serosa contains mesothelium whereas adventia does not

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160
Q

Where is adventitia located?

A

seen on organs that are fixed in place and not freely seen in a cavity

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161
Q

What does the esophagus look like?

A

1) relatively muscular tube that conveys chewed food and liquids from pharynx to
stomach by rapid peristaltic activity (about 25cm long)

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162
Q

What does the esophagus look like when it is not conveying chewed food to the stomach?

A

Lumen is normally collapsed except when food is passing through

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163
Q

What does the mucosa look like throughout the esophagus?

A

stratified squamous nonkeratinized epithelium

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164
Q

What does the submucosa look like throughout the esophagus?

A

1) dense irregular CT exhibiting longitudinal folds when relaxed
2) mucous secreting esophageal glands present

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165
Q

How does the muscularis externa vary in the esophagus?

A

Superior third - skeletal muscle
Middle third - skeletal and smooth muscle
Inferior third - smooth muscle

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166
Q

Is it covered by serosa or adventitia?

A

Superior third - adventitia (binds to other structures in the neck and thoracic cavity)
Inferior third - serosa (seen only after esophagus passes through diaphragm)

167
Q

What is the primary activity occurring in the stomach?

A

digestion and absorption begin in this expandable muscular-walled reservoir

168
Q

How is digestion accomplished in the stomach?

A

acidic fluid is added to the ingested food here and the muscular activity
transforms this mixture into a viscous semifluid mass called chyme

169
Q

What is chyme?

A

viscous semifluid mass

170
Q

What makes up gastric juice?

A
  • hydrochloric acid
  • pepsin (secreted initially as pepsinogen)
  • mucous
  • water and electrolytes
171
Q

What is the anatomy of the stomach?

A

Cardia
Fundus
Body
Pylorus

172
Q

What are rugae?

A

1) longitudinal folds present in the undistended stomach
2) flatten as stomach expands
3) mucosal covering and submucosal core

173
Q

What are gastric pits?

A

tubular invaginations

174
Q

What are gastric pits lined by?

A

lined by simple columnar mucous

secreting cells

175
Q

What are gastric glands?

A

compound tubular glands

176
Q

What does compound tubular mean?

A

Multiple branches of ducts

177
Q

What are gastric glands lined by?

A

lined by enzyme and acid secreting cells

178
Q

What are gastric glands surrounded by?

A

these epithelial structures are surrounded by lamina propria

179
Q

How is the stomach muscularis externa unique in the stomach?

A

has 3 layers:

1) inner/oblique
2) middle/circular
3) outer/longitudinal

180
Q

Why is the 3 layers of muscularis externa advantageous in the stomach?

A

1) necessary for the churning action required in the stomach

2) thickened on either end of the stomach to form sphincters

181
Q

What is the cardiac sphincter?

A

prevents reflux back into esophagus

182
Q

What is the pyloric sphincter?

A

regulates exit to duodenum

183
Q

Is this layer covered by serosa or adventitia?

A

serosa - covers all regions of the stomach

184
Q

Where is the cardiac region of the stomach?

A

narrow circular region (1.5-3cm in width) at junction between esophagus and stomach

185
Q

What kind of cells line the gastric pits and gastric glands?

A

simple columnar mucous secreting cells

186
Q

Are there any goblet cells in the stomach?

A

these cardiac glands are entirely mucous, no goblet cells though

187
Q

What is acid reflux or heart burn?

A

irritation to esophageal mucosa due to acid reflux from stomach

188
Q

What is the length relationship between the gastric pits and gastric glands in the fundus and body of the stomach?

A

gastric pits in these regions are relatively short

and gastric glands in these regions are relatively long

189
Q

What are Gastric pits and gastric glands are lined with?

A 
Surface mucous cells
Mucous neck cells
Parietal cells
Chief cells
Enteroendocrine cells
Stem cells
190
Q

Where are surface mucous cells?

A

line the luminal surface and the upper portion of the gastric pits

191
Q

What do surface mucous cells look like?

A

pale staining simple columar cells

192
Q

What kind of mucous do surface mucous cells secrete?

A

secretes a very thick, viscous protective mucous coating for stomach lumen

193
Q

Where are mucous neck cells?

A

located deep in the gastric pit or superficially in the gastric gland (i.e., neck)

194
Q

What do mucous neck cells look like?

A

pale staining simple cuboidal to columar cell

195
Q

What kind of mucous do mucous neck cells secrete?

A

secretes mucous (of a thinner nature than surface mucous cell mucous)

196
Q

Where are Parietal (Oxyntic) Cells located?

A

predominate cell type in the upper two-thirds of the gastric glands

197
Q

What do Parietal (Oxyntic) Cells look like?

A

large pyramidal to round cells

eosinophilic cytoplasm and sometimes binucleated

198
Q

What do Parietal (Oxyntic) Cells secrete?

A

secrete HCl

199
Q

Where are Chief (Zymogenic) Cells located?

A

usually limited in location to the lower third of the gastric glands

200
Q

What do Chief (Zymogenic) Cells look like?

A

have all the characteristics of a typical protein secreting cell
* basophilia, granular cytoplasm, nucleolus

201
Q

What do Chief (Zymogenic) Cells secrete?

A

secrete pepsinogen

202
Q

Where are Enteroendocrine Cells located?

A

located in the lower parts of the gastric gland

203
Q

What do Enteroendocrine Cells look like?

A

pale staining cell

204
Q

What is unique about the position of Enteroendocrine Cells’ secretory vesicles?

A

secretory granules are adjacent to the basement membrane

205
Q

What and where do Enteroendocrine Cells secrete?

A

secrete gastrointestinal hormones in response to luminal conditions

  • gastrin
  • motilin
206
Q

What effect does gastrin have?

A

stimulates acid production by parietal cells

207
Q

What effect does motilin have?

A

stimulates smooth muscle activity

208
Q

What do Gastric Stem Cells look like?

A

pale columnar cell difficult to distinguish from a mucous neck cell

209
Q

What do Gastric Stem Cells give rise to?

A

give rise to replacement cells for each of the stomach epithelial cell types

210
Q

What is the average life span of a mucous cell?

A

mucous cells have a life span of about 3-5 days

211
Q

What is the average life span of a parietal, chief or enteroendocrine cell?

A

parietal, chief and enteroendocrine cells have a life span of about 1 year

212
Q

Where is the Pyloric Region of Stomach?

A

evident where the body narrows as it gets close to the duodenum

213
Q

What is the importance of the pyloric sphincter?

A

thickening of the muscularis externa

which regulates the outflow from the stomach

214
Q

What is the length relationship of the gastric pits and the gastric glands in pyloric region of the stomach?

A

gastric pits are relatively long and gastric glands are relatively short

215
Q

What kind of cells line the gastric pits and gastric glands in the pyloric region of stomach?

A

predominately mucous secreting cells

216
Q

What is the most common cause of ulcers?

A

most commonly due to a chronic infection by helicobacterium pylori
- causes the protective mucous layer in the stomach to break down

217
Q

What happens as the stomach mucous breaks down?

A

acid in the stomach can eat away the epithelium and lamina propria

218
Q

What may happen in very severe cases of stomach ulcers?

A

in severe cases a hole can be made in the stomach wall

219
Q

Why are severe cases of stomach ulcers so dangerous?

A

Would allow gastric contents to enter the peritoneal cavity. This condition can lead to peritonitis and even death

220
Q

What are the two main functional activities of the small intestine?

A

digestion is completed and the products of digestion are absorbed here

221
Q

To optimize absorption and digestive activities, what must the small intestine prolong contact between?

A
  • chyme and digestive enzymes

- digested products and the absorptive cells of the epithelial lining

222
Q

What are the three sections of the small intestine?

A

Duodenum
Jejunum
Ileum

223
Q

What small interestinal features faciliate absorption?

A

Plicae circulares
Villi
Microvilli

224
Q

What is the gross anatomical appearance of plicae circulares?

A

circular mucosal folds with submucosal cores

225
Q

Where are plicae circulares most prevalent?

A

most prevalent in the distal duodenum and the jejunum

226
Q

How much do plicae circulares increase surface area?

A

increases intestinal surface area about 3-fold

227
Q

What is the villi histological structure?

A

finger-like mucosal projections with cores of lamina propria

228
Q

Where are they the villi most prevalent?

A

common throughout the small intestine

229
Q

How much do villi increase surface area?

A

increases intestinal surface area about 10-fold

230
Q

What is the histological structure of microvilli?

A

apical cytoplasmic extensions covered by cell membrane

231
Q

Where are microvilli most prevalent?

A

finger-like projections on luminal surface of the absorptive epithelial cells

232
Q

What provides support to microvilli?

A

actin cytoskeletal core linked to cell membrane and the terminal web

233
Q

What is the terminal web?

A

layer of actin at the apical side of cell

234
Q

What is terminal web function?

A

significantly increase membrane surface area available for absorption/secretion

235
Q

What is the striated border?

A

about 2000-3000 microvilli present on each cell that form a layer known as the striated border

236
Q

How much does does microvilli increase surface area?

A

increases intestinal surface area about 20-fold

237
Q

What is the cumulative increase in surface area resulting from plica circulares, villi and microvilli?

A

increase small intestinal surface area 600-fold to a total of about 200 square meters

238
Q

How is the small intestinal mucosa protected from carry-over gastric juice digestion?

A

mucosa is protected by mucous secreted by goblet cells and Brunner’s glands

239
Q

What enzymes do enterocytes secrete?

A

enterocytes secrete disaccharidases and dipeptidases

240
Q

What enzymes come from the pancreas?

A

1) trypsinogen, chymotrypsinogen and carboxypeptidase - digest protein
2) amylase - digests carbohydrates
3) lipase - digests lipids
4) deoxyribonuclease and ribonuclease - digest nucleic acids

241
Q

What comes from the liver for digestion in the small intestine?

A

bile salts - digest lipids

242
Q

What is the small intestional villi morphology?

A

cells (enterocytes) and goblet cells

243
Q

What kind of epithelial covering is present?

A

covered by simple columnar absorptive

244
Q

What does simple columnar mean?

A

Column shaped and one layer

245
Q

What is the distribution pattern for goblet cells?

A

goblet cells continually increase in number distally in the intestinal tract

246
Q

What layer forms the core of a villous?

A

Lamina propria

247
Q

What layer Contains neurovascular and lymphatic elements?

A

Lamina Propria

248
Q

Where are junctional complexes located?

A

found at apical end of columnar cells of GI tract

249
Q

What are the 3 components of junctional complexes ?

A 
zonula occludens (tight junction)
zonula adherens
macula adherens (desmosome)
250
Q

Why are zonula occudens known as a tight junction?

A

no intercellular gap exists (occludes the intercellular space)

251
Q

What are sealing strands?

A

IMPs on adjacent cells

252
Q

How does zonula occudens act as a barrier?

A

Controls travel through a cell instead of in between cells.

Prevents water soluble components but fat soluble are unaffected

253
Q

Why is it zonula occudens selectively leaky?

A

disallows travel between adjacent cells (selectively leaky)

254
Q

What is the difference between zonula occulens and zonula adherens?

A

Zonula occludens have no intercellular gap and function to be a selective barrier for entry into the lumen
Zonula adherens have intercellular gaps and function to lateral adhere epithelial cells and incorporate actin

255
Q

What is the terminal web of zonula adherens?

A

cytoskeletal elements incorporated internally by zonula adherens

256
Q

What is the function of a zonula adherens?

A

lateral adhesion between epithelial cells

257
Q

How is the strength compared to ZO?

A

Stronger as every zonula occudens is supported by a zonula adherens

258
Q

What is a Central Lacteal?

A

central lymphatic capillary

259
Q

What does a central lacteal do?

A

participate in the absorption and transport of lipids

260
Q

Where is Central Lacteal found?

A

in the lamina propria core of each villous

261
Q

How are products of fat digestion transported away from the small intestine?

A

1) products of fat digestion are monoglycerides and free fatty acids
2) these are absorbed by villous columnar cells and used in lipid synthesis
3) lipid-containing vesicles are produced and released into the intercellular space (deep to the junctional complexes)

262
Q

What are the produced fat globules known as?

A

Chylomicrons

263
Q

How does the delivery of chylomicrons into the blood differ from other metabolites?

A

chylomicrons reach the blood indirectly by first entering the lacteal and being transported by lymphatics

264
Q

What is the morphology of intestinal crypts?

A

simple or compound tubular invaginations between the villi and surrounded by lamina propria

265
Q

what does the Epithelial lining of intestinal crypts consist of?

A

simple columnar absorptive cells and goblet cells, paneth cells, enteroendocrine cells and crypt base stem cells

266
Q

What do paneth cells look like?

A

large cell with very large distinctive acidophilic cytoplasmic granules

267
Q

What do paneth cells do?

A

granules contain lysozyme (antibacterial)

268
Q

What do enteroendocrine cells look like?

A

pale staining columnar cell

269
Q

What do enteroendocrine cells do?

A

small basophilic secretory granules basally located in the cell

270
Q

What do the crypt base stem cells do?

A

may give rise to paneth, enteroendocrine, goblet or simple columnar absorptive cells

271
Q

How does Intestinal Mucosal facilitate absorption?

A

via striated border on enterocytes

272
Q

How does Intestinal Mucosal facilitate digestion?

A

via enzyme secretion by enterocytes

273
Q

How does Intestinal Mucosal provide protection?

A

via mucous secretion and junctional complexes

274
Q

Why is the small intestine lamina propria very well vascularized with type II capillaries?

A

involved in absorption of nutrients

275
Q

What kind of tissue is the lamina propria?

A

loose CT heavily populated with immune system cells (GALT)

276
Q

Why is there a lot of GALT in the intestines?

A

protection from ingested pathogens

277
Q

What are Peyer’s patches?

A

Aggregations of lymphoid nodules typically found in the ileum

278
Q

What does intrinsic innervation mean?

A

Regulation occurs within the structure

279
Q

What does extrinsic innervation mean?

A

Regulation occurs by nervous system

280
Q

Where is Auerbach’s myenteric plexus located?

A

Between two layers of the muscularis externa

281
Q

What activity does Auerbach’s myenteric plexus regulate?

A

regulates contractile activity of the muscularis externa

282
Q

Where is Meissner’s submucosal plexus located?

A

located in the submucosa

283
Q

What activity does Meissner’s plexus regulate?

A

regulates gastrointestinal secretion and local blood flow

284
Q

What effect does parasympathetic and sympathetic innervation have on intestinal activity?

A

Parasympathetic innervation - stimulates intestinal smooth muscle activity
Sympathetic innervation - depresses intestinal smooth muscle activity

285
Q

What are some distinctions in the duodenum?

A

1) Entirely retroperitoneal
2) receives ducts from liver and exocrine portion of pancreas
3) contains villi and crypts with moderate numbers of goblet cells
4) contains Brunner’s glands

286
Q

Where specifically are brunner’s glands located?

A

In the duodenum

287
Q

What do they Brunner’s glands secrete?

A

secrete alkaline mucoid material and urogastrone

288
Q

Why is all this mucous required in the duodenum?

A

1) protects mucosal surface by neutralizing the acidic chyme

2) brings pH up to an optimal level for pancreatic digestive enzymes to work

289
Q

What effect does urogastrone have?

A

inhibits acid secretion by the stomach

290
Q

What are some distinctions of the jejunum?

A

1) main absorptive unit in the small intestine
2) greatest number of plical folds with most complex arrangement of villi
3) Paneth cells are most easily seen here in the bottom of intestinal crypts

291
Q

What are some distinctions of the ileum?

A

1) greatest collection of GALT (Peyer’s patches)
2) goblet cells are most numerous here
3) villi and crypts present with rare Paneth cells
4) Brunners glands absent

292
Q

What is the primary function of large intestine?

A

completes absorption and retrieves water from luminal contents leaving
compact indigestible waste residue (feces)

293
Q

What and where are the regions of the colon grossly?

A

Cecum
Ascending, transverse, descending and sigmoid colon
Rectum
Anal Canal

294
Q

Are there any villi in the large intestine?

A

No, luminal surface is “smooth”

295
Q

Are there any crypts in the large intestine?

A

yes, fairly thick with deep crypts compared to the small intestine

296
Q

By what mechanism does digestion occur in the large intestine?

A

digestion may continue here as a result of residual enzymatic action as well as decomposition by bacteria

297
Q

Where does the mucous come from in the large intestine?

A

epithelial lining produces abundant mucous but no digestive enzymes

298
Q

What is absorbed in the large intestine?

A

mainly water

299
Q

What do the columnar absorptive cells do in the large intestine?

A

play no active role in digestion

primary function is water and electrolyte absorption

300
Q

What is the distribution pattern for the goblet cells in the large intestine?

A

increasing in number proportionately from ascending colon to rectum

301
Q

Are there stem cells present in the crypts in the large intestine?

A

located at the base of the crypts

mitotically replaces both the columnar absorptive and goblet cells

302
Q

What is the turnover rate for differentiated cells in the large intestine?

A

differentiated cells are shed in the lumen every 6 days or so

303
Q

How does the lamina propria and submucosa compare from small intestine to large intestine?

A

Pretty similar, except there are no submucosal Brunner’s glands

304
Q

Why are the lamina propria and submucosa of the large intestine usually rich in GALT?

A

presumably as a response to the abundant luminal bacterial population

305
Q

What are teniae coli?

A

longitudinal layer of smooth muscle arranged in three

longitudinal bands along the cecum and colon (lacking in the appendix)

306
Q

Are there any advantages of teniae coli in the large intestine?

A

maintain tonus and allow the remainder of the wall to sacculate

307
Q

What comprises the internal anal sphincter?

A

thickening of the circular layer of smooth muscle at the anal-rectal junction

308
Q

What controls internal anal sphincter activity ?

A

under autonomic control and responds to distension

309
Q

What comprises the external anal sphincter?

A

consists of skeletal muscle

310
Q

What controls external anal sphincter activity ?

A

voluntary control of defecation

311
Q

Is the large intestine covered by serosa or adventitia?

A

retroperitoneal segments of colon and rectum covered by adventitia and remainder is covered by serosa

312
Q

What is the epithelial transition at the anus?

A

simple columnar epithelium -> stratified squamous nonkeratinized -> stratified squamous orthokeratinized

313
Q

Where is the appendix?

A

blindly ending tubular diverticulum of the cecum

314
Q

What does appendix look like grossly?

A

about 5-10cm long; 0.8cm in diameter

315
Q

What does appendix look like histologically?

A

resembles other parts of the large intestine

316
Q

What is appendicitis?

A

results largely from blockage of its lumen or twisting

317
Q

Why does appendicitis occur?

A

1) prone to bacterial infection

318
Q

What is the risk associated with perforation of the appendix?

A

may become inflamed and risk perforation which would spread bacteria into peritoneal cavity (bacterial peritonitis)

319
Q

What is an appendectomy?

A

common surgical procedure to remove inflamed appendix

320
Q

What are the accessory glands of digestion?

A

1) Salivary Glands (Parotid, Submandibular, Sublingual)
2) Pancreas
3) Liver

321
Q

Where is the pancreas located?

A

mixed exocrine and endocrine gland located in the “C” shaped duodenal loop

322
Q

What is an exocrine gland?

A

Contains a duct

323
Q

What is an endocrine gland?

A

Does not contain a duct

324
Q

How can the pancreas be both?

A

Secretes enzymes through a duct and hormones directly into the blood

325
Q

What does compound acinar mean?

A

branched ducts with cluster of cells

326
Q

What percentage of pancreatic tissue is exocrine?

A

occupies the bulk of the pancreatic tissue (98 -99 %)

327
Q

What do the serous secreting cells look like?

A

1) very basophilic triangular shaped cells

2) basal spherical nucleus with apical zymogen granules

328
Q

What enzymes are produced in the pancreas?

A

1) trypsinogen, chymotrypsinogen and carboxypeptidase digest proteins
2) amylase digests carbohydrates
3) lipase digests lipids
4) ribonuclease and deoxyribonuclease digest nucleic acids

329
Q

Where are digestive enzymes delivered to?

A

Duodenum

330
Q

What percentage of pancreatic tissue is endocrine?

A

1-2%

331
Q

What do the pancreatic islets look like?

A

pale staining islets (of Langerhans) scattered throughout the exocrine pancreas

332
Q

Where are the hormones delivered to?

A

Blood

333
Q

What percentage of islet cells produce insulin? (beta cells)

A

70%

334
Q

What action does insulin have?

A

Lowers blood sugar

335
Q

What percentage of islet cells produce glucagon? (alpha cells)

A

15-20%

336
Q

What action does glucagon have?

A

Increase blood sugar

337
Q

What percentage of islet cells produce somatostatin? (gamma cells)

A

5-10%

338
Q

What action does somatostatin have?

A

Inhibits insulin and glucagon secretion

339
Q

Why is the liver described as the principal metabolic organ in the body?

A

organ where nutrients absorbed in digestive tract are processed for use by other
parts of the body

340
Q

What is the body’s largest compound gland?

A

Liver

341
Q

What are the functions of the liver?

A 
  carbohydrate metabolism and storage
  plasma protein and lipoprotein synthesis and secretion
  drug and alcohol detoxification
  bile formation and secretion
  fetal hematopoiesis
342
Q

How many lobes make up the liver?

A

2, left and right lobes

343
Q

Is the liver covered by serosa or adventitia?

A

Serosa

344
Q

What and where is the porta hepatis?

A

deep transverse fissure on inferior surface of liver (essentially a hilum)

345
Q

What enters the porta hepatis?

A

major blood vessels, ducts and lymphatics

346
Q

What percentage of blood enters the liver via the proper hepatic artery?

A

25% comes via proper hepatic artery

347
Q

Where is the blood from the proper hepatic artery coming from and what is its composition?

A

highly oxygenated arterial blood coming indirectly from aorta (via celiac trunk)

348
Q

What percentage of blood comes via the hepatic portal vein?

A

75% comes via hepatic portal vein

349
Q

Where is blood from the hepatic portal vein coming from and what is its composition?

A

1) poorly oxygenated but nutrient rich venous blood from the intestinal tract
2) Broken down products due to blood cell degradation in the spleen

350
Q

Does the blood from the hepatic portal vein and the proper hepatic artery mix
at the porta hepatis?

A

no, blood from these two vessels will mix in the liver sinusoids

351
Q

What are liver sinusoids?

A

sinusoids are type III capillaries located between the rows of hepatocytes

352
Q

What happens with the blood in the liver sinusoids?

A

Blood from the hepatic portal vein and the proper hepatic artery mix together

353
Q

Where does the venous drainage from the liver go?

A

drain from the liver via the hepatic venous system

354
Q

What is the path the efferent lymphatics use to exit the liver?

A

efferent lymphatics travel with the BVs and bile ducts and exit at the porta hepatis

355
Q

Why are there no afferent lymphatics?

A

???

356
Q

What are Bile canaliculi?

A

small bile ducts (canaliculi) that form in the liver parenchyma

357
Q

Where do the bile canaliculi drain into?

A

bile ducts

358
Q

What structures do bile ducts travel with?

A

Blood vessels and lymphatics

359
Q

What do bile ducts combine to become?

A

Right and left hepatic ducts

360
Q

What do the right and left hepatic ducts combine to form?

A

Common hepatic duct

361
Q

What do the common hepatic duct and cystic duct combine to form?

A

Common bile duct

362
Q

What are hepatocytes?

A

parenchymal cell of the liver

363
Q

What do hepatocytes do?

A

carries out all of the biochemical functions of the liver

364
Q

What do are some properties of hepatocytes?

A 
Euchromatic nucleus
Prominent nucleoli
Abundant mitochondria
Extensive RER and SER
Several Golgi apparati 
Abundant glycogen particles
365
Q

How does the hepatocyte nucleus appear?

A

large spherical and central with prominent nucleoli

366
Q

Why is there extensive rough endoplasmic reticulum in hepatocytes?

A

extensive for synthesizing plasma proteins and lipoproteins

367
Q

What is there extensive smooth endoplasmic reticulum in hepatocytes?

A

extensive for lipid and cholesterol synthesis and drug/alcohol detoxification

368
Q

Why are there several golgi apparatus in hepatocytes?

A

several typically present for packaging products for secretion

369
Q

Why are glycogen particles present in hepataocytes?

A

abundant for storing glucose

370
Q

Why does approximately 70% of the hepatocyte cell surface border sinusoids?

A

maximizes the surface area available for exchanging materials with the blood

371
Q

Why does approximately 15% of the cell surface border bile canaliculi?

A

facilitates secretion into the bile duct system

372
Q

What’s happening along the remaining 15% of the cell surface?

A

both adhering and communicating junctions are present

373
Q

What happens to most of the water, cholesterol and ions in the body?

A

largely reabsorbed and recycled in the gut

374
Q

Why are the bile salts important?

A

1) facilitate digestion and absorption of fats in the intestines
2) largely reabsorbed in the gut and recycled to the liver

375
Q

Where does the bilirubin come from?

A

waste product of hemoglobin degradation in the spleen

376
Q

What happens to conjugated bilirubin?

A

excreted in the feces and gives them color

377
Q

How does bile get from the liver to the duodenum?

A

bile is transported in bile ducts from liver to gall bladder where it is stored and concentrated prior to excretion into duodenum

378
Q

What is the gall bladder used for?

A

bile is transported in bile ducts from liver to gall bladder where it is stored and concentrated

379
Q

What does a jaundiced person look like?

A

creates a distinctive yellow color (easily seen in skin and sclerae

380
Q

Why does the jaundice yellow color occur?

A

1) excess bilirubin pigment accumulates in blood and tissues

2) results from inadequate removal of bilirubin from blood by hepatocytes

381
Q

Why would excessive erythrocyte degradation lead to jaundice?

A

causes extra bilirubin from destroyed RBC’s resulting on inadequate removal of excess bilirubin

382
Q

How could hepatocyte problems cause jaundice?

A

The removal of the bilirubin via the conjugated form is impaired and thus bilirubin builds up in the blood and tissues without being properly removed

383
Q

What about gall stones?

A

Gall stones are due to the calcification of bile typically in the bile ducts therefore obstructing the bile duct and causing pain

384
Q

What is the typical diameter of a liver sinusoid?

A

sinusoids are vascular channels 10-30m in diameter

385
Q

What kind of endothelium is present in liver sinusoids?

A

lined by a discontinuous, highly fenestrated endothelium

386
Q

Is there a basement membrane in liver sinusoids?

A

the basement membrane is discontinuous or missing from large areas

387
Q

What is the perisinusoidal space or space of Disse?

A

space located between the rows of hepatocytes and the sinusoidal endothelium

388
Q

What structures extend from the hepatocytes into the perisinusoidal space?

A

the microvilli extending from the hepatocytes

389
Q

Why do hepatocytes have microvilli in the perisinusoidal space?

A

increase the surface area about 6x

390
Q

What is significant about the space of Disse?

A

this is the space in which bidirectional transfer occurs between the hepatocytes and the blood plasma

391
Q

What are Kupffer cells?

A

permanent population of sinusoid-associated macrophages that are derived from monocytes

392
Q

Where are Kupffer cells located?

A

line the sinusoid and sometimes span across the sinusoidal lumen

393
Q

What do Kupffer cells do?

A

keep the sinusoid clear of particulate

394
Q

What happens to Kupffer cell activity following splenectomy?

A

subsequent to splenectomy, play an active role in erythrocytic turnover

395
Q

What is the classic liver lobule?

A

Basically hexagonal with rows of hepatocytes and sinusoids radiating away from the center

396
Q

What and where is the central vein?

A

this is the initial hepatic venule at the center of the classic lobule

397
Q

What drains into the central vein?

A

the liver sinusoids drain to the central vein

398
Q

Where does the central vein ultimately drain to?

A

heptic venous system?

399
Q

Where are the portal triads located in the classic liver lobule?

A

found in Connective Tissue portal tracts at the corners of the hexagonal lobule

400
Q

What kind of blood is in the hepatic portal vein?

A

1) nutrient rich venous blood from the intestines

2) venous blood from the spleen containing bilirubin

401
Q

What kind of blood is in the hepatic artery?

A

oxygen rich blood (indirectly from the aorta)

402
Q

How does bile flow in the classic liver lobule?

A

bile duct carries bile away from the hepatocytes

403
Q

How does blood flow in the classic liver lobule?

A

from hepatic portal vein and/or hepatic artery into liver sinusoids and out via the hepatic vein

404
Q

Where does the lymphatic vessel go from the liver lobule?

A

???

405
Q

A liver acinus is a functional model of liver tissue in relationship to what?

A

relation to its blood supply

406
Q

How does the liver acinus shape and location relate to the classic liver lobule?

A

corresponds to roughly ovoid mass of liver parenchyma extending over contiguous regions of two adjacent classic lobules

407
Q

Where is zone 1 in the acinus located?

A

located at the contiguous borders of 2 classic liver lobules

408
Q

Why is zone 1 in the acinus described as being a relatively privileged location?

A

1) nearest the portal triads and furthest from the central vein

409
Q

Why are cells in zone 1 in the acinus least susceptible to hypoxia?

A

hepatocytes in this zone receive nutrient rich and oxygen rich blood primarily

410
Q

Why are in zone 1 in the acinus most susceptible to blood borne toxins?

A

hepatocytes in this zone receive first contact with the toxins

411
Q

Where is zone 3 in the acinus located?

A

these liver cells are furthest from the portal triads and closest to the central vein

412
Q

Why is zone 3 in the acinus described as being a less desirable location than zones 1 and 2?

A

blood delivered here is low in oxygen and nutrients

413
Q

Why are cells here most susceptible to ischemic necrosis?

A

these hepatocytes are most susceptible to ischemic necrosis (due to hypoxia)

414
Q

Why are these cells the last to respond to blood borne toxins?

A

last to respond as they are furthest away from contact to the toxins

Histology (9 decks)

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