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Unit 5 > Histology Of Connective Tissue > Flashcards

Histology Of Connective Tissue Flashcards

1
Q

What is the embryonic origin of connective tissue?

A

Mesenchyme from the mesoderm layer

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2
Q

Where is connective tissue often found?

A

It is the most abundant tissue in the body often found between layers of other tissue.

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3
Q

What is the overall function of connecctive tissue?

A

To support and bind substances together.
Provide cushioning and protection
Medium for diffusion
Defend against infection

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4
Q

What is the general structure of all connective tissue?

A
  1. Cells
  2. Protein Fibres
  3. An amorphous ground substance
    The fibres and ground substance make up the ECM
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5
Q

What is a ground substance?

A

Provides a holding dish for other structures
Is mainly water for exchange.
Resist compression and tension, aids communication such as diffusion
Made out of GAGs (glycosaminoglycans) attached to a protein backbone to form proteoglycans.
May also contain glycoprotein.
GAGs affect diffusion, turgor and attract water.

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6
Q

What are the different protein fibres and their function?

A
  1. Collagen - most abundant provides tensile strength
  2. Elastic - contains elastin and fibrillin proteins, stretch and recoil without deformation
  3. REticular fibres - contain type 3 collagen, provides support to parenchyma of lymphatic organs and the spleen, stained black by agrophilic (silver) methods whilst surrounding lymphocytes appear pink.
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7
Q

What are the different types of collagen?
What is a good way to remember this?

A

1 - aggregates in fibre bundles, most abundant, ECM, bone and skin
2- No fibres, found in elastic and hyaline cartilage
3 - Reticular Fibres, surrounds smooth muscle, nerves, stroma of organelles and organs
4 - no fibrils, chemically unique, forms basal lamina
5 - found in the placenta
Boys Can Resolve Basic Problems
Bone, Cartilage, Reticular Fibres, BAsement membrane, Placenta

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8
Q

Give an overview of the different types of cells found in connective tissue.

A

Cells can be fixed/resident meaning they stay in the same tissue area. These cells are often derived from mesenchymal cells including adipocytes, fibroblasts, osetocytes, chondrocytes, endothelial and mesothelial cells.
Cells can be transcient/mobile, so can move between tissue areas. These typically orignate from haematopoietic stem cells e.g lymphocytes and neutrophils

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9
Q

What is the deal with fibroblasts?

A

The most abundant cell type found in most connective tissue.
Secrete collagen and elastin to make up the ECM
Cells are ovoid shape, but normally only the nucleus is identifiable on the histological slide
An oval nucleus indicates it is active whilst an elongated nucleus with a darker stain indicates it is inactive.
Often found near collagen.

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10
Q

What are the different classifications of connective tissue?

A

1) Dense - regular or irregular
2) Loose - areola, adipose or reticular
3) specialised - bone, cartilage, lymph, blood

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11
Q

Give an overview of loose connective tissue?

A

Is highly cellular (mainly fibroblasts), with a random arrangement of fibres (mainly collagen) with an abundant ground substance
Often found just below the basement membrane in the dermis.
Fills the space between structures and holds them in place,

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12
Q

What is the deal with white adipose tissue?
Function
Origin

A

A type of loose connective tissue
Develops from mesochyme into lipoblasts with small fat vacules then into adipocytes.
Stores fat/lipids for energy
Provide cushioning and protection
Role in shivering thermogenesis

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13
Q

How does white adipose tissue appear on histological slide?

A

Unilocular.
Appear white and empty as filled by one large fat vacuole.
Smaller peripheral cytoplasm with a cresent shaped nucleus
Clump together to form lobules separated by a connective tissue septa of fibroblasts, blood vessels and lymphatic drainage.
many fine capillaries supply the adipocytes.

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14
Q

What is the deal with brown adipose tissue?

A

Found predominantly in new born infants, changes to white adipose tissue as age
Found mainly in the back, neck, shoulders, para-aortic regions and perirenal regions.
Large number of mitochondria and rich capillary blood supply.
Role in non-shivering thermogenesis

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15
Q

What does brown adipose tissue look like in a histological image?

A

Each cell contains many lipid droplets described an multilocular, so looks more patchy and eosinophilic.
Mitochondria and rich blood supply give it the brown colour.

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16
Q

Give an overview of dense connective tissue?

A

Dense connective tissue has more collagen fibres, little ground substance and fewer cells. Provides resistance to stretching
regular - highly vascularised, type 1 collagen in parallel arrangement with fibroblasts.
irregular - collagen fibres not organised, resist tensile forces from many directions, poorly vascularised,

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17
Q

Where is dense regular and dense irregular connective tissue found?

A

Regular - tendons and ligaments
Irregular - dermis of the skin

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18
Q

What are the different types of connective tissue membranes?

A

Mucus membranes - passages continous with external world e,g DT, RT,
Serous membranes - line body cavities e.g peritoneum
Synovial membranes - joints often with articular cartilage

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19
Q

What is Ethers-Dandlos syndrome?

A

Mutation in collagen gene or proteins associated with collagen metabolism.
Spontaneous or inherited
Very rare, exists on a spectrum
Results in hypermobility of joints and greater skin laxity

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20
Q

What is Marfan Syndrome?

A

Mutation or disfunction in the fibrillin gene
Causes problems with elastic fibres in connective tissue.
Patients are often longer limbed, long digits, longer upper body section, very thin.
More vulnerable to aneurysm, heart defects and lens dislocation

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21
Q

What is cartilage?
Origin, classification and function

A

Type of specialised connective tissue
Avascular, no lymphatic or innervation
Recieves nutrition by diffusion
Consists of chondrogenic cells (cytes and blasts) in an ECM
Provides: tensile strength, structural support, flexibility without distortion, friction free movement, shock absorbed and resilience to compression.
orignates from mesenchyme

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22
Q

Give an overview of the cells and their arrangement found in cartilage.

A

Chondroblasts develop into chondrocytes
Chondroytes are surrounded by lacunae (box style), many chondrocytes group together into isogenous groups.
Territorial matric within the group and an interterritorial matrix between groups
Chondroblasts and found near the perichondrium (if present).

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23
Q

What is the perichondrium?

A

A layer of connective tissue found on the edges hyaline (not articular)and elastic cartilage.
Made of an outer fibrous layer (vascular) and an inner chondrogenic layer, acts as a connective tissue capsule.

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24
Q

What is the deal with hyaline cartilage?

A

Contains type 2 collagen fibres.
Plays a role in endochondral bone formation, meaning chondrocytes die as the matrix ossified, results in reduced joint mobility and pain as cartilage disintigrates
A growth plate is often found below hyaline cartilage
Found in the respiratory tract, costal cartilages and the articular surfaces of long bones.

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25
Q

What is the deal with elastic cartilage?

A

Matric contains a large amount of collagen and elastin so can recoil after deformation
Outer fibrous perichondrium is also rich in elastic fibres
Found in the ear and epiglottis.

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26
Q

What is the deal with fibrocartilage?

A

Has no perichondrium
Parallel arrangements of chondrocytes, type 1 collagen and fibroblasts.
Provides resistance to mechanical forces and tensile forces
Can be found in association with hyaline cartilage
Found in between the vertebrae and in the pubic symphysis

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27
Q

What are the two different types of cartilage growth?

A

1) Interstitial cartilage growth
2) Appositional cartilage growth
Can occur simultaneously, but interstitial cartilage growth is required initially.

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28
Q

What is the deal with interstitial cartilage growth?

A

Enlarges the cartilage from within
Mesenchymal cells aggregate forming centres of chondrogenesis
Kartogenin allos cells in chondrogenesis centres to become chondroblast
Secrete cartilage matrix, which acts to surround each cell in a lacunae, becoming chondrocytes.
As matrix secretion continues the cells are pushed apart further enlarging the cartilage

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29
Q

What happens during appositional cartilage growth?

A

Inner cells in the perichondrium in the chondrogenic layer differentiate into chondroblasts.
Chondroblasts secrete type 2 collagen and ECM components
This adds new layers to the surface of cartilage.

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30
Q

Give an overview of bone.

A

Bone is highly vascular consisting on osteo cells, fibres and ECM.
Type of specialised connective tissue
Important location for haemopoiesis, reservoir for inorganic minreals and attachment for muscles
Stores 99% of the bodies calcium

31
Q

What is the deal with the organic components of bone?

A

Organic components are 85% type 1 collagen, makes up 35% of the bone weight.

32
Q

What is the difference between primary and secondary bone?

A

Primary - is mainly found in the embryo with abundant osteocytes and irregular collagen bundles
Secondary - before and after birth bone starts to become secondary bone, this is more organised and is split into spongy and compact bone.

33
Q

What are osteoprogenitor cells?

A

Stem cells that become osteoblasts

34
Q

What are osteoblasts?

A

Immature osteocytes
Synthesise type 1 collagen which becomes mineralised by calcium and phosphate deposits.
Secrete osteocalcin which binds to calcium and phosphate to from hydroxyapatite crystals
These secretions are the initial matrix called osteoids and separate the osteblasts from calcified bone
Appear basophilic when active.

35
Q

What are osteocytes?

A

Form from osteoblasts trapped within the bone they have made, secrete substances to regulate bone remodelling

36
Q

What is a good way to remeber the basic function of osteoclast and osteoblasts?

A

B = build
C = crush

37
Q

What are osteoclasts?
How do they bring about their effect?

A

Multinucleate cells derived from blood monocytes
Erode mineralised bone and osteoid collagen be enzymatic hydrolysis.
Stimulated by parathyroid hormone in response to low blood calcium, inhibited by calcitonin.
The eroded area of bone is called a subosteoclastic compartment which can increase greatly in size to beomce a Howship Lacuna.

38
Q

What allows connection between lacunae?

A

Canaliculi

39
Q

What are the different sections of a long bone?

A

Epiphysis
Metaphysis
Diaphysis/shaft

40
Q

What is a periosteum?

A

Lines the outside of the bone.
Outer dense irregular connective tissue layer and an inner layer of osteogenic cells.
Surrounded by an outer layer of nerves and blood vessels

41
Q

What lines the spongy bone trabecula?

A

Endosteum

42
Q

What are lamellae in the bones made of?

A

Type 1 collagen fibres with bone salts and crystal (calcium phosphates)

43
Q

What are sharpey fibres?

A

Connect the periosteum to the outer circumfrential lamellae in bone.

44
Q

What are the different arrangements of lamellae in compact bone?

A

Outer circumferential lamellae - found deep to the periosteum
Inner circumferential lamellae - found superficial to the spongy bone
Concentric lamellae - make up part of osteon
Interstitial lamellae - found in between osteons.

45
Q

What is an osteon?

A

Layers of concenteric lamella surrounding central canals which contains neurovasculature and connective tissue.
Between layers of lamellae are lacunae containing osteocytes which communicate with each other by dendritic extensions called canaliculi.

46
Q

How does neurvasculature travel around the compact bone?

A

Through vertical central canals in osteons
These central canals are linked horizontally by volkman canals, these allow bundles to travel from the periosteum to the spongy bone.

47
Q

Give an overview of bone development

A

Bone is formed during embryogenesis.
It can be formed by intramembranous or endochondral development.
Both result in primary bone initially, which is later resorbed and replaced by secondary bone. Secondary is resorbed at a slower pace as we age.

48
Q

What is endochondral ossification?

A

The change inutero from hyaline cartilage to bone.

49
Q

What happens during intramembranous bone development?

A

No cartilage is involved.
Mesenchymal cells differentiate and proliferate into osteoblasts.
These secrete osteoid forming the ECM.
Angiogenesis results in new blood vessels which can then transport calcium to help with the mineralisation of bone.
Osteocytes develop into osteoblasts when incorporated into osteoid, surrounded by lacunae.

50
Q

What is osteoid?

A

Unmineralised organic tissue secreted by osteoblasts.

51
Q

What happens during endochondral ossification?

A

1)Embryogenesis - mesenchymal cells = chondroblasts. Resulting in a perichondrium and cartilage model.
2) Perichondrium becomes more identifiable and cartilage starts to mirror the expected shape of the bone.
3) At the mid-shaft of the diaphysis the perichondrium becomes periosteum as osteoprogenitor cells and osteoblasts develop
4) A collar of bone is produced by intramembranous development. Calcium salts are deposited causing the bone to grow in size
5) Blood vessels grow through the periosteum and bone collar transporting osteoprogenitor cells to establish a primary ossification centre in the diaphysis.
6)Bone trabecula spread out from within the primary ossification centre to link with the bone collar, bone collar becomes compact bone
7)the terminal epiphysis (cartilage) become secondary ossification centres at birth, supplied by blood vessels.

52
Q

What is osiffication?

A

making of bone from osteoblasts

53
Q

When does bone growth stop for long bones?

A

When there is no more cartilage between the diaphysis and the epiphysis

54
Q

What happens in secondary centres of ossification?

A

Postnatal development of bone
Chondrocytes in the resting zone
Chondrocytes proliferate and grow in size (hypertrophy)
Are ossified are calcium is deposited from blood vessels and chondrocytes themselves secrete cartilage matrix and organic material.\
Become osteoblasts secreting osteoid on a calcified matrix.

55
Q

What happens in primary centres of ossification?

A

Resting zone of normal hyaline cartilage
Zone of proliferation - isogenous groups of chondrocytes divide thickening the cartilage layer
Zone of maturation and hypertrophy of chondrocytes, alkaline phosphates are produced resulting in subsequent calcification of the cartilage matrix
Zone of degeneration where chondrocytes die, leaving empty lacunae surrounded by calcified cartilage
Zone of ossification - bone is deposited on calcified cartilage increasing the length of the diaphysis
Zone of resorption - calcified cartialge bone is resorbed to form the marrow space.

56
Q

What is osteoperosis?

A

Age related loss of bone mineral density, common in females after menopause due to decreased oestrogen levels leading to increased osteocyte levels.
Affected bones have lower calcium levels and are easier to fracture.
Is often treated with oestrogen therapy, increasing calcium uptake and calcitonin to inhibit bone resorption.

57
Q

What is osteoarthiritis?

A

A cartilage disease.
Loss of cartilage leads to bone on bone contact with the synovial joint, this rapidly reduces movement and function.
Associated with a decrease GAGs and water in the matrix.
Mainly affects hyaline cartilage in weight bearing areas.

58
Q

What type of bones is intramembranous ossification associated with?

A

Flat bones

59
Q

What is shown in the image?

A

Black reticular fibres and pink lymphocytes
In the lymph node
Stained by argyrophilic methods

60
Q

What is shown in the image?

A

Fibroblasts nuclei parallel to collagen bundles
Left image shows active fibroblasts
Left inmate includes elongated nuclei on inactive fibroblasts

61
Q

What is shown in the image?

A

Loos connective tissue
Thicker pink collagen bundles
Thin black elastic fibres
Fibroblasts nuclei
Surrounded by a ground matrix

62
Q

What is shown in the image?

A

Loose connective tissue
H+E stain so elastic is not black, fibres are finger than collagen
Fibroblasts nuclei

63
Q

What is shown in the image?

A

Dense irregular connective tissue
Fibroblast nuclei and collagen fibres bundles

64
Q

What is shown in the image?

A

White adipose tissue
Arranged into lobules with a connective tissue septa

65
Q

What is shown in the image?

A

Mainly multilocular brown adipose tissue

66
Q

What is shown in the image?

A

Dense regular connective tissue
Parallel arrangement of fibroblast nuclei with collagen, little ground matrix

67
Q

What is shown in the image?

A

Final blank is articular surface of bone, into the synovial fluid

68
Q

What is shown in the image?

A

Elastic cartilage, with Perichondrium at the bottom of the image

69
Q

What is shown in the image?

A

Fibrocartilage with hyaline cartilage at the bottom

70
Q

What is shown in the image?

A

Elastic cartilage but with a H&E stain so look like pink thin wispy lines rather than black wispy lines

71
Q

What is shown in the image?

A

Compact bone, osteons with a central canal, note the concentric lamellae, irregular lamellae at the bottom of the image

72
Q

What is shown in the image?

A

Fibrous periosteum
Inner circumferential lamellae
Outer circumferential lamellae
Osteons
Central canal

73
Q

What is the role of parathyroid hormone in bone homeostasis?

A

PTH stimulates bone resoprtion
Secreted when blood calcium is too low, binds to and activates osteoclasts, which break down the mineralised component of bone to increase blood calcium levels

74
Q

What is the hormonal role of calcitonin?

A

Calcitonin is secreted when blood calcium levels of too high.
Binds to and activates osteoblasts to absorb calcium and deposit it in the bone matrix, this lower the blood calcium level back to normal.

Unit 5 (12 decks)

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