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Histology - Section 2 > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What are the four main functions of Connective TIssue?

A
  1. Structural support
  2. Medium for exchange
  3. Aid in defense and protection of the body
  4. Site of fat storage
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2
Q

Embryonic Connective Tissue

A

Mesenchyme

Mucous CT

  • Wharton’s jelly
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3
Q

Connective Tissue Proper

A

Loose (areolar)

Dense irregular

Dense regular

Reticular

Adipose

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4
Q

Specialized Connective Tissue

A

Cartilage

Bone

Blood

  • Hemopoietic
  • lymphatic tissues
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5
Q

Where is Dense Irregular Connective Tissue located?

A

Dermis of skin,

sheaths of nerves,

capsules of spleen,

kidney,

lymph nodes,

testes and ovaries

Fills spaces just deep to skin, mosothelial lining of body cavity, blood vessel adventitia, surrounds parenchyma of glands, lamina propria of gastrointestinal tract

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6
Q

Where is dense regular connective tissue located?

A

Tendons (muscle to bone),

ligaments (bone to bone)

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7
Q

What is ground substance of the extra-cellular matrix composed of?

A

1) Glycosaminoglycans (GAGs) - Polysaccharides of repeating disaccharide subunits - Sulfated e.g. keratan, chondroitin, and dermatan sulfate - Attracts water, resists compression - Unsulfated - hyaluronic acid is central protein to which they are attached
2) Proteoglycans (PGs) - Protein core with covalently bound sulfated GAGs - Important for binding and activation of growth factors
3) Glycoproteins - Include fibronectin, laminin, entactin - Contain domains that bind components of ECM and integrins

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8
Q

Describe the composition and function of collagen fibers (part of ECM)

A
  1. Major fibrous protein of connective tissue
  2. Flexible, high tensile strength
  3. Generally < 10 µm diameter, wavy fibers that stain pink with H&E
  4. Formed by assembly of tropocollagen molecules
    - Each tropocollagen molecules consists of triple helix of 3 α- chains
    - Every third amino acid is glycine
    - Other amino acids are mainly proline, hydroxyproline, and hydroxylysine
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9
Q

Describe the eight steps of collagen synthesis.

A
  1. Transcription in nucleus
  2. Translation of preprocollagen in RER. α- chains with propeptides at amino- and carboxyterminal ends
  3. Hydroxylation in RER
  4. Glycosylation in RER
  5. Formation of procollagen triple helix in RER
  6. Secretion of procollagen via trans Golgi network
  7. Cleavage of propeptides by procollagen peptidase to form tropocollagen molecule
  8. Spontaneous self-assembly of tropocollagen to form collagen fibril
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10
Q

What are the Seven major forms of collagen?

A
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11
Q

What are the reticular fibers?

A

Form fine meshwork (reticulin) in liver, bone marrow, and lymph system

  1. Type III collagen
  2. Thin ( 0.5 - 2 µm), branched
  3. Poorly stained with H&E but
    well stained with silver and
    PAS stains
  4. Prevalent in lymphatic,
    hematopoietic tissues,
    spleen, liver and other glands
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12
Q

Elastic Fibers in Skin and their defects

A

Consist of Type 1 collagen and elastic fibers ( elastin core, and fibrillin microfibers).

Clinical Correlates

  1. Scurvy:
    Deficiency of Vitamin C which is cofactor for
    proline hydroxylase
  2. Ehlers-Danlos syndrome:
    Mutation in collagen gene or
    enzyme related to collagen
    metabolism (extreme flexibilty and loose skin; rupture in gut/intestine)
  3. Marfan’s syndrome:
    Defect in fibrillin gene

Rupture of gut/intestine. Muscular arteries are lacking elastic material. RUPTURE OF AORTA

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13
Q

What are the Fixed/Resident cells in tissues?

A

Fixed/resident cells

  • Fibroblast - arise from mesenchymal cells. Predominant cells in connective tissue. Can differentiate and produce collagen
  • Pericyte - derive from embryonic mesenchymal cells and may retain pluripotenital. Located mostly in capillaries. Differentiate into endothelial cells, fibroblasts, and smooth muscle cells in response to injury
  • Adipocyte - arise from mesenchymal cells and fibroblasts. Fully differentiated, they sythesize, store and release fat
  • Mast cell - arise from myeloid cells. Contain primary and secondary mediators (mediate inflammation, activate coplement. attract lymphocytes, vasodilate, and other aspects of immune response)
  • Histiocyte (macrophage) - arise from monocytes and migrate into connective tissue. Phagocytic cells.
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14
Q

What are the transient/wandering cells?

A

Transient/wandering cells

  • Macrophage - phagocytic cells arising from monocytes in the bone marrow.
  • Lymphocyte - arise from lymphoid stem cells. Consist of B-cells (humoral immune reponse), T-cells (cell-mediated response) and Natural Killer cells (anti-tumor cells)

• Granulocytes - white blood cells that contain cytoplasmic granules
- Neutrophils, Eosinophils, Basophils

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15
Q

What role do fibroblasts have in the cell?

A
  1. Principal cell of CT
  2. Myofibroblasts
    -Resemble smooth muscle cells
    -Play role in wound closure and
    healing
  3. Pericytes
    -Undifferentiated mesenchymal
    cells associated with capillaries
    and small venules
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16
Q

What are the different adipocytes and what is their function?

A

Unilocular adipocytes

  • White/yellow fat
  • Lipid storage

Multilocular adipocytes

  • Brown fat
  • Thermogenesis
17
Q

What is the purpose of unilocular adipocytes?

A
  1. Stored lipid mainly triglycerides
    -Synthesized in adipocyte
    -Synthesized in liver and
    imported as VLDL
  2. Mobilization of lipid under
    hormonal and neurogenic
    control
    -Triglycerides broken down to
    fatty acids and glycerol
  3. Adipocytes produce leptin
    - Decreases food intake
    - Increases energy consumption
18
Q

What is the purpose of multilocular adipocytes?

A
  1. 2-5% of body weight in human
    newborn
  2. Brown coloration due to
    cytochromes present in
    mitochondria
  3. Mitochondria contain
    thermogenin which allows back
    flow of H+ ions across inner
    membrane
  4. Rich capillary bed
  5. Production of heat controlled
    by sympathetic innervation
19
Q

What are the two types of obesity?

A
  1. Hypertrophic obesity
    - Adult onset
    - Increase in cell size
  2. Hypercellular obesity
    - Childhood onset
    - Increase in cell number
20
Q

What are macrophages and where do they come from?

A
  1. Principal phagocytic cells
    of CT
  2. Originate in bone marrow
    as monocytes
    -Part of mononuclear
    phagocyte system
  3. Fuse to form foreign body
    giant cells
21
Q

The mononuclear phagocyte system is circulating monocytes originating from bone marrow that end up in different locations. What are the names of the monocytes in each part of the body?

A
22
Q

What are Plasma Cells?

A
  1. Originate from B
    lymphocytes
  2. Characteristic
    “cartwheel” nucleus,
    basophilic cytoplasm
  3. Abundant at sites of
    chronic inflammation
  4. Synthesize and secrete
    immunoglobulins
23
Q

What are Mast Cells and what do they do?

A
  1. 20-30 µm diameter
  2. Originate from bone marrow
  3. Mediate inflammatory response
    -Basophilic granules contain
    primary mediators (heparin,
    histamine, eosinophil and
    neutrophil chemotactic factors
    -Synthesize and secrete
    secondary mediators
    (Leukotrienes, thromboxanes,
    prostaglandins)
  4. Hypersensitivity reaction -
    anaphylactic shock
24
Q

How are Mast cells activated?

A

Basic:

1) Bee Stings
2) Body makes antibodies against bee venom
3) Antigen is presented to mast cells by embedding antibody into mast cell membrane
4) Mast cell is now primed to repond to next appearance of venom (1st reaction is mild, 2nd is rapid and extreme)

Complex:

1) Antigen binds to IgE receptor complex.
2) Activates adenylate cyclase
3) Activates protein kinase
4) Phosphorylates proteins that activate primary and secondary mediators

Primary Mediator

5) Calcium released -> Granules fuse -> Granule’s contents released.

Secondary Mediator

5) Activate phospholipases -> Convert arachidonic acid in membrane -> secrete leukotrienes, thromboxanes, prostaglandins

25
Q

What are the three main types of cartilage and where are they found?

A

1) Elastic cartilage: Pinna of ear, epiglottis
2) Hyaline cartilage: Cartilage of nose, costal cartilage, articular cartilage (knee and hip)
3) Fibrocartilage: Intervertebral disk, meniscus

26
Q

What are the cartilage cells? What is cartilage made of?

A
  1. Cartilage Cells
    - Chondrogenic cells
    - Chondroblasts
    - Chondrocytes
  2. Ground substance
    -GAGs and PGs
    -Fibers
    Hyaline cartilage - type II collagen
    Elastic cartilage - type II collagen + elastic fibers
    Fibrocartilage - type I collagen
27
Q

What is the composition of bone?

A

•Bone matrix

  • Osteoid (naturally quite flexible. Cells deposit calcium to mineralize and harden)
  • Type I collagen, GAGs, and PGs
  • Hydroxyapatite (Ca10(PO4)6(OH)2)

•Cells

  • Osteoprogenitor cell
  • Osteoblast
  • Osteocyte
  • Osteoclast
28
Q

What are the different classifications of bone?

A

Compact bone: outer layer which is very hard

Spongy bone: composed of interconnected trabeculae with a layer of osteoblasts and filled with osteocytes. Has cavities filled with bone marrow

29
Q

What is the organization of compact bone?

A

Osteons, made of lacunae (growth like rings) surrounding Haversian canals that carry blood vessels and nerves and connective tissue.

Volkman canals interconnect haversian systems and carry the neurovascular supply.

Canaliculi are small channels connecting lacunae. (gap junctions)

There are no haversian systems in spongy bone.

30
Q

What are the cells of the bone?

A
  1. Osteoblasts (derived from osteo-progenitor cells)
    -Synthesize osteoid (organic
    components of bone matrix)
    -Deposit inorganic components
    -Located at surfaces of bone tissue
  2. Osteocytes (mature osteoblasts)
    -Derived from osteoblasts
    -Sit in lacuna surrounded by bone
    matrix
    -Connect to other osteocytes via
    gap junctions between cytoplasmic
    processes in canaliculi
    -Maintain bone matrix
  3. Osteoclasts (derived from the mononuclear-phagocyte system)
    -Large, motile, multinucleate cells
    -Make contact with bone matrix via
    ruffled border
    -Secrete enzymes that breakdown
    bone matrix resulting in depression
    called Howship’s lacuna
31
Q

What is the function of osteclasts?

A

1) To break down bone so that it can be remodeled later.
2) To release calcium from the bones (calcium reservoir)
3) Osteoclasts break bone down, Osteoblasts replace it, and a channel is left through the middle

32
Q

What are some clinical correlates of bone deficiencies?

A

1.Osteoporosis
-Estrogen dependent decline in osteoblast
activity

  • Affects men and women, but men show no results because they have more bone mass
  1. Osteomalacia (Rickets)
    - Disturbance in bone mineralization
  • Pregnant women need to take caclcium and vitamin D because the fetus is taking calcium
  1. Osteosarcoma
    - Malignant tumor derived from osteoblasts
33
Q

What are the two types of bone formation?

A
  1. Intramembranous bone formation (Flat bones)
    - Mesenchymal condensation into ossification centers, differntiate into osteoblasts, and secrete osteoid. Calcification occurs
  2. Endochondral bone formation (Long and short bones)
    - Hyaline cartilage model
    - Primary center of ossification is at the midriff of diaphysis. Bone collar forms.
    - Secondary center of ossification at epiphyses. Bone extends lengthwise at ephiphyseal plate.
34
Q

What are the two methods of bone growth?

A

•Increase in diameter
-Subperiosteal appositional
growth

•Increase in length
-Extension at epiphyseal plates

35
Q

What are the three main types of leukocytes and what do they do?

A

1) Neutrophils
- phagocytic
- digest bacteria
2) Eosinophils
- Attack parasites
3) Basophils
- Inflammatory Response

36
Q

What are mesenchymal cells?

A

Found only in embryos - gel-like amorphous matrix containing a few reticular fibers. Pluripotential cells.

Histology - Section 2 (2 decks)

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