Lecture 3:Tissue Cells and ECM

Question 1

Tissues

Answer 1

Tissues are formed by cells and an ECM

And intricate mesh work of proteins and polysaccharides that are secreted by the cell

Question 2

Connective tissue

Answer 2

Is made from several types of fixed and wandering cells. Has abundant amount of ECM and the function is for support and structure

CT forms a continuum with ET and MT and NT as well as other components to maintain a functionally integrated body

Question 3

Functions of CT

Answer 3

Support and protection

Forms a resolve of factors controlling growth and differentiation

Provides medium through which nutrients and metabolic waste can exchange between

Question 4

Structural elements of CT

Answer 4

ECM

-protein fibres, collagen reticular and elastic

• ground substances
  Macromolecules and multi adhesive glycoproteins that stabilise the ECM

Question 5

Fibroblasts

Answer 5

The most common cell in CT

Production of givers and ground substances

Synthises ECM components such as collagen elastin glycosaminoglycans

Fibroblasts have intense synthetic activity. They are different from the quiescent cells that are scattered and have already synthesises called fibrocytes

Question 6

Fibroblasts structure

Answer 6

They have large active nuclei and eosinophilic cytoplasm

Spindle shapes nucleus

The nuclei are clearly seen but the collagen bundles in the cytoplasm are hard to distinguish

Question 7

Macrophages

Answer 7

Derive from bone marrow precursors that divide producing monocytes that circulate in the blood

Monocytes cross the wall of the venules and capillaries to penetrate the CT where they mature and acquire the features of macrophages. ( increase cell size, protein synthesis, number of golgi and lysosomes)

Along with other monocytes derived cells they comprise of a family called mononuclearphagocyte system

Long living cells that survive for months

Question 8

Mast cells cytoplasm

Answer 8

Their cytoplasm is filled with basil Phillip secretory granules
-heparin: a sulfated glycosamine that works as an a anticoagulant

Histamine- promotes increased vascular permeability and smooth muscle contraction

Serene protease- activates various media totes of inflammation

Eosinophils factors- they attract leukocytes

Question 9

Mast cells

Answer 9

They originate from stem cells in the bone marrow

They are large and oval shaped CT cells and they are 20-30 um in diameter

They can change the colour of some basic dyes so toluidine blue to red or purple

They have immediate hypersensitivity reactions. Meaning it occurs after the same antigen enters the body again

Question 10

Pericytes

Answer 10

They’re surrounded by cells of capillaries and small venules

Have their own basal lamina And are technically outside the CT compartment

Derived from mesenchymal cells

They possess characteristic of endothelial cells and smooth muscle cells. Function is contraction

Question 11

Plasma cells

Answer 11

Anti body producing cells derived from B cells

Large ovoid cells that have a basiophillic cytoplasm due to the richness of rough ER

The nucleus is spherical by eccentrically placed within the cell

Question 12

Development of fat cells

Answer 12

A fibroblast precursor cell is converted into a mature fat cel by the accumulation of lupus droplets

This process is partially reversible

The cells in the early and intermediate stages can divide but the mature fat cells cannot

Question 13

Mesenchymal cells

Answer 13

Undifferentiated cells

Spindle shaped

They gave extended process that is in contacts with other cells via gap junction

Question 14

ECM

Answer 14

Protein fibres- proteins that polymerise into elongated structures

• collagen
• reticular
• elastic

Ground substances

• Gags
• proteoglycans

Question 15

Collagen fibres

Answer 15

Most abundant protein in the human body

Representing 30% of it’s dry weight

The collagen a are produced by fibroblasts and several other cells types

There are more than 20 types of collagen that have been identified and named via Roman numerals

Question 16

Structure of collagen

Answer 16

It is composed of a triple helix structure composed of 3 Alpah PP chains

The alpha chain consists of repeated triplet sequences

Collagen type one is the most abundant and widespread

Question 17

6 major collagen types

Answer 17

1 - CT, bone and dentin 
2- hyline and elastic cartilages 
3-reticular fibres 
4-lamina densa of Basal lamina 
5-in placenta, associates with type 1 
7- attaches basal lamina to lamina reticularis

Question 18

Collagen fibrillogenesis

Answer 18

Pro collagen- collagen- collagen fi

RER
-synthesis of pro alpha chain 
-self assembly of 3 pro alpha chains 
To form the triple helix 
GOLGI
-sorting pro collagen into secretory granules 
-exocytosis 

Then collagen fibril formation

Question 19

Classification of collagen

Answer 19

Fibroblasts Forming
1,2,3,5,11

Fibroblasts associated
9,12

Network forming
4,7

Question 20

Fibril associated

Answer 20

Mediate the interaction of collagen fibrils with one another and with other metric macromolecules

Question 21

Network forming

Answer 21

Fibril structure is absent in 4 and 7 bc the peptides are not removed from the pro collagen molecule

It’s pro collagen forms diners and then forms a mesh work

Question 22

Collagen turnover

Answer 22

In normal CT it is a slow process

To me renewed the collagen must first be degraded

Degradation is Initated by a specific enzyme called collagenase

Question 23

Collagen and disease

Answer 23

Genetic
-osteogenesis type 1

Non genetic
-liber chirrosis

Question 24

Reticular fibres

Answer 24

Consists mainly of collagen type 3

Form networks of very thin but glycosylated fibres in certain organs

Abundant in the spleen lymph nodes and bone marrow

Question 25

Elastic fibres

Answer 25

Thinner than collagen fibres

Forms networks interspersed with collagen bundles in organs.

Elastin is the major component. It is a globular molecule and are secretes by fibroblasts in CT

Question 26

Elastic fibre structure

Answer 26

The core of elastic fibres is composed of elastic and is surrounded by a sheath of microfibrils

Elastin is held by 4 lysine molecules that form covalent bonds with each other to form desmosine cross links

Question 27

Ground substances

Answer 27

They are highly hydrophilic complexes of macromolecules

• GAGS
• proteoglycans

Multiadhesive glycoproteins stabilise the ECM
-laminin
By Binding to receptors proteins on the surface of cells

Question 28

GAGs

Answer 28

Unbranched, extended polysaccharide

Question 29

PG

Answer 29

Consists of protein core molecules bound with GAGs

Function- acts as co receptors of growth hormones