Connective Tissue

Question 1

Generally, what does connective tissue do?

Answer 1

binds, supports and holds together the tissues and organs of the body

Question 2

Where is connective tissue derived from?

Answer 2

MESODERM

Question 3

What are the three types of connective tissue (resist to pulling and stretching forces) ?

Answer 3

1) loose (areolar) connective tissue
2) Dense irregular connective tissue
3) dense regular connective tissue

Question 4

What are the four types of SPECIALIZED connective tissue?

Answer 4

have unique properties and functions in addition to supporting and protecting

1) blood
2) cartilage
3) bones
4) adipose tissue

Question 5

Cartilage and bones give (a) to soft tissues of the body

Answer 5

STRUCTURE

Question 6

What two main categories are CT made of?

Answer 6

cells + extracellular matrix

Question 7

What makes up the ECM of CT?

Answer 7

fibers, ground substance, associative elements

Question 8

Three types of CT fibers

Answer 8

1) elastic fibers
2) collagen fibers
3) reticular fibers

Question 9

Elastic Fibers

Answer 9

found wherever tissues need to stretch and return to original shape

hydrophobic AA alternated with lysin domains

crosslinked by lysyl oxidase, associates into microfibrils (THICKER = more elastin)

Question 10

collagen fibers included 3 types we need to know

Answer 10

MOST COMMON FIBER IN ECM

Type I: most common type, 90%, CT, bone, tendon, skin… resist tension

Type III (aka reticular fibers): loose CT, organ, blood vessels

Type IV: basement membrane, support and anchor epithelial cells

Question 11

How collagen fibers are made

Answer 11

there are 3 left handed alpha subunits
in the ER need proline, glycine and hydrolases (intermolecular H bonds) that form procollagen

Procollagen is a R handed triple helix

It then goes into the ECM, where it gets cleaved by peptidases, then they get covalently bonded to one another by lysyl oxidase

Question 12

Reticular fibers

Answer 12

made of reticular cells, specialized type of collagen (Type III), support hematopoietic organs

argyrophilic (stained with silver)

Question 13

What is the ground substance of the ECM ?

Answer 13

water, gelatinous

transparent and fills spaces between fibers of ECM and CT cells

lubricant + barrier

has proteoglycans

Question 14

What makes up proteoglycans and what do they attract?

Answer 14

protein core + glycosaminoglycan (GAG)

long sugars with sulfate attract NA+ which attracts H20 ions

Question 15

What are the types of connective tissue cells?

Answer 15

1) migratory
2) resident which includes fibroblast, reticular cells
3) adiopocytes

Question 16

Migratory cells

Answer 16

come from hematopoetic stem cells in blood

immune system cells= inflammatory response (basophils, eosonphils)

populate LOOSE connective tissue

Question 17

where do resident cells come from

Answer 17

undifferentiated mesenchymal cells

Question 18

Fibroblast

Answer 18

MOST abundant type of CT cell

make collagen + elastin fibers (ie. making ECM components)

Question 19

Reticular cells

Answer 19

specialized fibroblast
in haemopoietic + lymphatic tissue

makes type III collagen–> reticular fiber

meshwork

antigen presentation, cytokine production for lymphocyte

Question 20

adiopocytes

Answer 20

fat cells
make up adipose tissue

energy storage as triglycerides to mobilize between meals

shapes body, shock absorber, thermal insulation

Question 21

What do associate elements do?

Answer 21

connect cells to the ECM

ie. fibronectin, entactin, tenascin, laminin

Question 22

Integrins

Answer 22

glycoproteins associated to fibers in ECM and to cellular receptors

Question 23

Basement membrane (aka basal lamina)

Answer 23

thin sheets of ECM outlining epithelia, muscle fibers, blood vessels, peripheral nerves

structural attachment site for overlaying epithelia and underlying connective tissue

Question 24

Loose connective tissue (function, features)

Answer 24

most abundant type of CT

little tensile strength, LOW mechanical stress (LOW friction), holds blood supply (O2 and nutrient diffusion)
inflammatory + immune function

HIGH ground substance (white)
HIGH cells
collagen + elastin fibers

Question 25

Dense irregular connective tissue

Answer 25

mechanical support LESS cells, LESS ground substance (LOTS of pink, not a tone of white) mostly type I collagen fibers in heavy bundles randomly orientated fibers to withstand stress from many directions

Question 26

Dense regular connective tissue

Answer 26

mechanical coordination type I collagen tendons, ligaments, cornea LESS cells, LESS ground substance fibers packed, oriented in parallel array to withstand stress from ONE direction

Question 27

Cartilage (and how it is made generally)

Answer 27

semi rigid, cushions places where bone may rub against bone produced by chondroblast/ chondrocytes when mesenchymal cells differentiate into chondroblasts--> secrete the cartilage matrix and become in small spaces known as lacunae--> once entrapped = condrocytes

Question 28

Perichondrium

Answer 28

dense outer layer surrounding cartilage | ONLY hyaline and elastin, NOT fibrocartilage

Question 29

What makes up cartilage?

Answer 29

generally ground substance and collagen type II | for fibroblasts includes collage type I

Question 30

Three types of cartilage

Answer 30

1) hyaline 2) fibrocartilage 3) elastic cartilage

Question 31

Hyaline cartilage

Answer 31

most abundant in type II collagen transparent, smooth WITHOUT apparent fibers smooth texture = LOW friction and HIGH lubricant articular surfaces has chondrocytes and perichondrium

Question 32

Fibrocartilage

Answer 32

also have increase concentration of collage type I chondrocytes lining up in distinct rows NO perichondrium compression and pulling forces like meniscus or interverbal discs

Question 33

elastic cartilage

Answer 33

histologically similar to hyaline matrix mostly type II collagen, but ALSO HAS elastic fibers has perichondrium,

Question 34

Bone main function and composition

Answer 34

Ca2++ homeostasis, support + protect organs bone marrow at center 70% calcium 30% collagen type I

Question 35

Three types of bone cells responsible for bone synthesis and breakdown

Answer 35

osteoblasts: synthesize and mineralize bone, LINE THE SURFACE osteocytes: osteoblasts that are entrapped in bony matrix - -> sit in lacunae in the bone, nutrient and metabolite diffusion osteoclasts: break down and digest bony matrix, on surface in howship lacunae, multinucleated

Question 36

how osteoclasts break down bone

Answer 36

on surface in howship lacunae, osteoblasts stimulate osteoclasts to move inside bone --> seal off bone surface --> secrete enzymes (HCl) --> ingest remnants by phagocytosis

Question 37

Two types of bone

Answer 37

1) compact / cortical | 2) trabecular / spongy/ cancellous

Question 38

Compact (aka cortical) bone

Answer 38

outer surface of bone ~80 % mass structural unit: osteon, haversian system

Question 39

Trabecular (aka spongy aka cancellous) bone

Answer 39

porous network in interior supports compact bone 20% mass but GREATER surface area = increased mineral exchange and more specialized function

Question 40

ECM of bone

Answer 40

osteoblasts, type I collagen, non collagen proteins

Question 41

Two types of bone formation

Answer 41

1) endochondral ossification | 2) intramembraneous ossification

Question 42

Endochondral ossification

Answer 42

FORMING IN THE CARTILAGE... long bones 1) osteoblasts deposit calcified material into carticlage and forms bone collar 2) chondrocytes die and primary ossification center forms 3) bone invades diaphysis and ossification expands 4) secondary ossification center forms 5) epiphyseal growth eventually seals in adolescence

Question 43

Intramembraneous ossification

Answer 43

from Mesenchyme directly cranial bones and flat bones like scapula 1) mesenchymal cells differentiate into osteogenic and capillaries --> then differentiate to osteoblasts and form clusters --> ossification centers 2) osteoblasts secrete bone matrix organic component known as osteoid--> become trapped as they are mineralizing--> now osteocytes... osteoblasts differentiate on edge of osteoid 3) clusters of osteoid will unite --> form trabecular network... superficial surface forms periosteal layer containing osteoblasts 4) periosteal layer creates compact bone surrounding spongy interior