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2A PRELIM > HISTO AI > Flashcards

HISTO AI Flashcards

1
Q

What are the four basic tissue types in the human body?

A

Epithelial, connective, muscular, and nervous tissues

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2
Q

What is the primary function of epithelial tissues?

A

Covering, lining, and protecting surfaces; absorption; secretion

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3
Q

What is the extracellular matrix (ECM)?

A

A network of proteins and molecules that provides structural and biochemical support to surrounding cells

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4
Q

What distinguishes connective tissue from other tissue types?

A

It has abundant extracellular matrix produced by its cells

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5
Q

What are the two main components of an organ’s structure?

A

Parenchyma and stroma

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6
Q

What is the role of parenchyma in an organ?

A

It is composed of cells responsible for the organ’s specialized functions

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7
Q

What is the role of stroma in an organ?

A

It consists of supportive cells, usually connective tissue, except in the brain and spinal cord

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8
Q

What are the characteristic features of epithelial cells?

A

Closely aggregated polyhedral cells adhering strongly to one another and to ECM

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9
Q

What is the basement membrane?

A

A thin extracellular layer that supports epithelial tissues and acts as a filter

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10
Q

What are the two parts of the basement membrane identified by electron microscopy?

A

Basal lamina and reticular lamina

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11
Q

What components are characteristic of the basal lamina?

A
  • Type IV collagen
  • Laminin
  • Nidogen
  • Perlecan
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12
Q

What is the function of tight junctions in epithelial cells?

A

They form a seal between adjacent cells, preventing passive flow of materials

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13
Q

What are adherens junctions?

A

Sites of strong cell adhesion in epithelial tissues

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14
Q

What is the function of gap junctions?

A

Channels for communication between adjacent cells

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15
Q

What is the difference between apical and basal poles of epithelial cells?

A

The basal pole contacts the ECM, while the apical pole faces a space

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16
Q

Fill in the blank: Epithelial cell nuclei may be ______, spherical, or flattened.

A

[elliptic (oval)]

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17
Q

True or False: Most epithelia contain blood vessels.

A

False

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18
Q

What are papillae in relation to epithelial tissues?

A

Small evaginations from connective tissue into the epithelium that increase contact area

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19
Q

What is the role of the basement membrane in epithelial repair?

A

It serves as a scaffold allowing rapid epithelial repair and regeneration

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20
Q

What are myoepithelial cells?

A

Contractile cells found within certain epithelia

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21
Q

What is the significance of tight junctions in maintaining cell polarity?

A

They restrict movement of membrane proteins and lipids, maintaining distinct apical and basolateral domains

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22
Q

List the main functions of the basement membrane.

A
  • Provides structural support
  • Attaches epithelia to connective tissue
  • Acts as a filter
  • Regulates macromolecular exchange
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23
Q

What proteins are involved in tight junctions?

A
  • Claudin
  • Occludin
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24
Q

What happens when tight junction proteins are disrupted by pathogens?

A

It can lead to loss of tissue fluid and other pathological conditions

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25
Q

What is the role of proteins of tight junctions in medical applications?

A

They provide targets for certain common bacteria of medical importance.

For example, the enterotoxin from Clostridium perfringens binds claudin molecules and disrupts tight junctions.

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26
Q

What effect does Helicobacter pylori have on tight junctions?

A

It binds the extracellular domains of tight-junction proteins and disrupts signaling from the junction.

This is linked to the etiology of gastric ulcers.

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27
Q

What is the function of the adherens junction?

A

It provides points linking the cytoskeletons of adjacent cells and strengthens nearby tight junctions.

This junction encircles the epithelial cell immediately below the tight junction.

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28
Q

What are the major transmembrane link proteins of tight junctions?

A

Occludins, claudins, ZO proteins.

These proteins are crucial for the integrity of tight junctions.

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29
Q

What is the main function of desmosomes?

A

They provide points of strong intermediate filament coupling between adjacent cells, strengthening the tissue.

Desmosomes resemble spot welds rather than forming a belt around cells.

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30
Q

What are the major components of gap junctions?

A

Connexins that form hexameric complexes called connexons.

These structures allow for intercellular communication.

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31
Q

What is the primary function of hemidesmosomes?

A

They anchor the cytoskeleton to the basal lamina.

Hemidesmosomes link to laminin molecules.

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32
Q

What are microvilli and their function?

A

Cytoplasmic projections that increase the apical surface area for better absorption.

They are particularly prominent in absorptive cells lining the small intestine.

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33
Q

Fill in the blank: Microvilli are usually _____ long and _____ wide.

A

1 μm long and 0.1 μm wide.

They can increase the total surface area by 20-30 fold.

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34
Q

What medical condition is characterized by loss of the microvilli brush border?

A

Celiac disease.

This condition results from an immune reaction against gluten.

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35
Q

What is the difference between stereocilia and microvilli?

A

Stereocilia are longer, less motile, and may branch distally.

They are found in the male reproductive system and inner ear sensory cells.

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36
Q

What are cilia and their primary function?

A

Long, highly motile apical structures containing microtubules; they facilitate movement of substances along the epithelial surface.

Primary cilia are non-motile and involved in signal transduction.

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37
Q

True or False: Desmosomes are responsible for cell-to-cell adhesion.

A

True.

They provide strong adhesion through intermediate filaments.

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38
Q

What intracellular structures are linked to the adherens junctions?

A

Actin filaments.

These filaments form part of the terminal web in epithelial cells.

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39
Q

What is the function of focal adhesions?

A

They link integrins to actin filaments and are involved in cell signaling, adhesion, and mobility.

Focal adhesions are important during epithelial repair and in migrating cells.

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40
Q

What are the major functions of tight junctions?

A

Seals adjacent cells, controlling passage of molecules between them; separates apical and basolateral membrane domains.

Defects in tight junctions can lead to various medical conditions.

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41
Q

What is a primary cilium?

A

A short projection on most cell types, enriched with receptors and signal transduction complexes for detection of light, odors, motion, and liquid flow.

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42
Q

What are motile cilia?

A

Cilia abundant on cuboidal or columnar cells that are typically 5-10 μm long and 0.2 μm in diameter.

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43
Q

What is the structural composition of a typical cilium?

A

A core structure with nine peripheral microtubule doublets and two central microtubules, known as the axoneme.

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44
Q

What proteins are involved in the movement of cilia?

A

Kinesin and cytoplasmic dynein motors.

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45
Q

What is the function of cilia?

A

To move a current of fluid and suspended matter in one direction along the epithelium.

46
Q

How does ciliary motion occur?

A

Through changes in the conformation of the axoneme facilitated by dynein-powered sliding of adjacent doublets.

47
Q

What is Kartagener syndrome?

A

A condition caused by mutations in cilia and flagella proteins, leading to chronic respiratory infections and immotile spermatozoa.

48
Q

What are the two main groups of epithelia?

A

Covering (or lining) epithelia and secretory (glandular) epithelia.

49
Q

Define simple epithelia.

A

Epithelia composed of one cell layer.

50
Q

Define stratified epithelia.

A

Epithelia composed of two or more layers of cells.

51
Q

What are the three types of simple epithelial cell shapes?

A
  • Squamous
  • Cuboidal
  • Columnar
52
Q

What is the primary function of stratified squamous keratinized epithelium?

A

Protection against dehydration.

53
Q

Where is stratified squamous nonkeratinized epithelium found?

A

In moist internal cavities such as the mouth, esophagus, and vagina.

54
Q

What is unique about transitional epithelium?

A

It can distend and is characterized by dome-like superficial cells.

55
Q

What is the role of pseudostratified columnar epithelium?

A

Protection, secretion, and cilia-mediated transport of particles.

56
Q

What are the characteristics of simple cuboidal epithelium?

A

Cells are roughly as tall as they are wide, allowing for high levels of active transport.

57
Q

Fill in the blank: Stratified cuboidal epithelium is found in _______.

A

[the excretory ducts of salivary and sweat glands]

58
Q

What is the function of the basal body in cilia?

A

To anchor the axoneme to the apical cytoplasm.

59
Q

True or False: Stratified columnar epithelium is commonly found.

A

False

60
Q

What is transcytosis?

A

The process by which substances are transported across a cell.

61
Q

What are the protective functions of stratified squamous epithelia?

A

Protection against invasion by microorganisms and water loss

Particularly important in the epidermis

62
Q

What happens to differentiating cells in the epidermis of stratified squamous epithelium?

A

They become keratinized, lose their nuclei and organelles, and form flattened squames

This process helps impede water loss

63
Q

Where can nonkeratinized stratified squamous epithelia be found?

A

Esophageal lining and outer covering of the cornea

These cells retain their nuclei and provide protection against microorganisms

64
Q

What are the functions of stratified cuboidal or columnar epithelia?

A

Occur in excretory ducts of certain glands, such as sweat glands

They allow additional functions due to their double layer of cells

65
Q

True or False: Chronic bronchitis leads to decreased numbers of goblet cells in the airways.

A

False

It leads to an increase in goblet cells and excessive mucus production

66
Q

What is the primary function of secretory epithelia?

A

To produce and secrete various macromolecules

This can include proteins, lipids, or carbohydrate-protein complexes

67
Q

What are unicellular glands?

A

Scattered secretory cells in simple cuboidal, simple columnar, and pseudostratified epithelia

An example is the goblet cell in the small intestine

68
Q

What do goblet cells secrete?

A

Lubricating mucus

This aids the function of the small intestine and respiratory tract

69
Q

What is the difference between exocrine and endocrine glands?

A

Exocrine glands have ducts and secrete substances to specific organs, while endocrine glands lack ducts and release hormones into the bloodstream

Endocrine glands are rich in capillaries

70
Q

What are the three basic mechanisms of secretion?

A
  • Merocrine secretion
  • Holocrine secretion
  • Apocrine secretion

Each mechanism involves different processes of product release

71
Q

What is merocrine secretion?

A

The most common method of secretion involving exocytosis from membrane-bound vesicles

Seen in protein or glycoprotein secretion

72
Q

Describe holocrine secretion.

A

Cells accumulate product, undergo terminal differentiation, and release product and cell debris into the gland’s lumen

Best seen in sebaceous glands

73
Q

What occurs during apocrine secretion?

A

Product accumulates at the apical end of cells, which then pinch off to release the product

This process is seen in mammary glands for lipid droplets

74
Q

What are serous cells?

A

Cells that synthesize proteins, mostly not glycosylated, and stain intensely with basophilic or acidophilic stains

Found in acini of the pancreas and parotid salivary glands

75
Q

What distinguishes mucous cells from serous cells?

A

Mucous cells contain heavily glycosylated proteins called mucins that form mucus when hydrated

Goblet cells are an example of mucous cells

76
Q

What type of cells assist in the propulsion of secretory products in exocrine glands?

A

Myoepithelial cells

These cells help contract and propel secretory products from acini into the duct system

77
Q

How do endocrine glands release their products?

A

By exocytosis for proteins and by diffusion for lipophilic steroids

Hormones are transported in blood to target cells

78
Q

What is transcellular transport?

A

The transfer of ions and water across the epithelium via ion pumps and aquaporins

Apical tight junctions prevent paracellular diffusion

79
Q

Where are key sites for ion and water transport in the body?

A

Epithelia of kidney tubules

These cells are specialized for maintaining the body’s overall balance of salts and water

80
Q

What are the key sites for ion and water transport in the kidney?

A

Helia of kidney tubules

They maintain the body’s overall balance of salts and water.

81
Q

What structural specialization do proximal renal tubule cells have for transcellular transport?

A

The apical surface is freely permeable to Na+ and basolateral membranes have sodium pumps

This allows for the active extrusion of Na+ into the interstitial fluid.

82
Q

What maintains osmotic and electrical balance in proximal renal tubule cells?

A

Passive transfer of chloride ions (Cl−) and water into the cell.

83
Q

How is the basal membrane of proximal renal tubule cells structured?

A

Elaborately folded with mitochondria located between the folds.

84
Q

What process allows all cells to internalize extracellular molecules and fluid?

A

Endocytosis and formation of cytoplasmic, membrane-bound vesicles.

85
Q

What is transcytosis?

A

The process of moving substances across a cell via vesicles, occurring in simple cuboidal and columnar epithelia.

86
Q

How often is the intestinal epithelium replaced?

A

Every week.

87
Q

Where do stem cells and mitosis occur in stratified epithelial tissues?

A

Only within the basal layer in contact with the basal lamina.

88
Q

What are malignant tumors of epithelial origin called?

A

Carcinomas.

89
Q

What are adenocarcinomas?

A

Malignant tumors derived from glandular epithelial tissue.

90
Q

What happens to epithelial tissues after major damage?

A

Cells of undamaged regions quickly begin active proliferation to regenerate tissue.

91
Q

What is dysplasia in epithelial cells?

A

Abnormal growth that can progress to neoplasia.

92
Q

What is metaplasia?

A

Transformation of one type of epithelial tissue into another type under abnormal conditions.

93
Q

What is the defining feature of simple glands?

A

Ducts do not branch.

94
Q

What type of secretion is characteristic of merocrine glands?

A

Release of products via exocytosis.

95
Q

How do holocrine glands release their secretions?

A

By disintegration of the secretory cells themselves.

96
Q

What distinguishes apocrine secretion?

A

Loss of membrane-enclosed apical cytoplasm containing lipid droplets.

97
Q

What are the three major types of intercellular junctions in epithelia?

A

Tight junctions, adherent junctions, and gap junctions.

98
Q

What do tight junctions prevent?

A

Paracellular passage of substances.

99
Q

What are adherent junctions formed by?

A

Interacting proteins of the cadherin family.

100
Q

What is the function of gap junctions?

A

Allow passage of small molecules from one cell to another.

101
Q

What is the basal lamina composed of?

A

Type IV collagen and laminin.

102
Q

What is the role of hemidesmosomes?

A

Attach cells to proteins of the basal lamina.

103
Q

What structures increase the apical surface area for absorption in epithelial cells?

A

Microvilli.

104
Q

What are stereocilia?

A

Long microvilli with specialized mechanosensory function.

105
Q

What is the axoneme in cilia?

A

A 9 + 2 arrangement of microtubules.

106
Q

What characterizes simple epithelia?

A

One cell layer.

107
Q

What type of epithelium is protective against urine?

A

Transitional epithelium or urothelium.

108
Q

What are exocrine glands characterized by?

A

Epithelial ducts carrying secretions to specific sites.

109
Q

What distinguishes endocrine glands?

A

Lack ducts and secrete hormones into the bloodstream.

110
Q

What types of glands produce mucus?

A

Mucous glands.

111
Q

What types of glands produce enzymes?

A

Serous glands.

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