Connective Tissue

Question 1

function of connective tissue

Answer 1

• support
• connection
• separation
• fat storage and insulation (adipose)
• transport of fluid and nutrients

Question 2

most abundant protein in humans

Answer 2

collagen

Question 3

types of connective tissue

Answer 3

Question 4

structure of connective tissue

Answer 4

• specialised cells e.g. chondrocytes, osteocytes
• ECM
  > fibres e.g. collagen, elastin, reticular
  > ground substance e.g. proteoglycans, glycosaminoglycans, glycoproteins
  (vascularised)

Question 5

fibroblast

Answer 5

• long, skinny cells
• secrete collagen fibrils into ECM which thicken and form connective tissue
• (most abundant cell)

Question 6

fibrocyte

Answer 6

• ageing/not very active fibroblast

Question 7

pericyte

Answer 7

• closely associated with blood vessel, may have some stem cell capabilities

Question 8

reticular fibres

Answer 8

• small, skinny, narrow fibre in ECM
• form a delicate mesh/framework to support cells
• type III collagen

Question 9

collagen

Answer 9

• long, thin, coarse band of fibre
• can be small and delicate or large/thick bundle

Question 10

elastin fibres

Answer 10

• strong fibres that can stretch and recoil e.g. arteries or pinna

Question 11

proteoglycans

Answer 11

• fill the space between cells + fibres
• bottlebrush shape
• protein core with branches of glycosaminoglycans (GAGs)
• strong net -ve charge: binds to cations e.g. Na+ > intensely hydrated

Question 12

where do specialised connective tissue cells come from?

Answer 12

• embryonic mesoderm > mesenchymal cells > specialised cells

Question 13

types of collagen

Answer 13

• I: bones, tendons, ligaments
• II: cartilage
• III: muscles, arteries, organs
• IV: basement membrane

Question 14

structure and function of ground substance

Answer 14

• S = gel-like substance made of proteoglycans, glycoproteins, glycosaminoglycans
• F = nutrient and waste diffusion, mechanical support

Question 15

characteristics of loose CT

Answer 15

• flexible
• lots of ground substance, few fibres and cells
• generally located between + surrounding organs
• e.g. areolar, reticular, adipose

Question 16

characteristics and types of dense CT

Answer 16

• inflexible
• lots of fibres, few specialised cells
• regular (tendons/ligaments): regular parallel fibres, unidirectional strength
• irregular (skin/alveoli): mesh-like arrangement, multi-directional strength
• elastic

Question 17

structure of cartilage

Answer 17

• chondrocytes sitting in lacunae (holes) in ECM
• ECM contains type II collagen, proteoglycans and glycoproteins
• chondrocytes don’t migrate easily and it’s avascular > poor growth and repair however ECM allows for diffusion of nutrients from vessels into cartilage

Question 18

2 ways cartilage can grow

Answer 18

• appositional: new cartilage @ surface of existing cartilage
• interstitial: mitosis of chondrocytes within existing cartilage

Question 19

structure, function, examples of hyaline cartilage

Answer 19

• S = surrounded by perichondrium for a new source of chondrocytes (except articular cartilage)
• F = development of foetal skeleton (most bones form from hyaline cartilage), growth in long bones (epiphyseal plate)
• e.g. articular cartilage, costal cartilage, nose, larynx, bronchi, trachea (most widespread cartilage)

Question 20

structure and examples of elastic cartilage

Answer 20

• S = surrounded by perichondrium, elastin in ECM (for bending), lots of chondrocytes
• e.g. pinna, eustachian tube, epiglottis, nose

Question 21

structure and examples of fibrocartilage

Answer 21

• S = combination of hyaline cartilage and fibrous tissue, no definite perichondrium, ECM contains type I (typical of CT) and II collagen (typical of hyaline)
• found in sites where strong compressive force is experienced e.g. intervertebral discs, pubic symphysis, meniscus

Question 22

structure of bone

Answer 22

• specialised CT: mineralised ECM which stores Ca and P
• collagen I
• constantly remodelling Haversian canals e.g. pregnancy, exercise, ageing
• good repair capacity b/c very well vascularised and innervated
• periosteum contains osteoprogenitor cells
• internal surface = endosteum > includes osteoprogenitors, osteoclasts + osteoblasts and contains bone marrow

Question 23

compact bone

Answer 23

• lamellae/rings of collagen deposited by osteoblasts
• Haversian system (osteon) runs parallel to long axis = Haversian canal containing nerves + capillaries, surrounded by several lamellae
• osteocytes located in lacunae between lamellae
• Volkmann’s canals run in opposite direction (perpendicular)

Question 24

spongy/cancellous/trabecular bone

Answer 24

• lamellae do NOT form Haversian systems, instead run in a 3D network trabeculae/spicules
• osteocytes located in lacunae (holes) between lamellae (layers)

Question 25

osteoprogenitor cells

Answer 25

• precursors of osteoblasts (stem cell)
• line periosteum and endosteum

Question 26

osteoblasts

Answer 26

• build bone by depositing osteoid (immature bone) and controlling its mineralisation
• become trapped in lacunae in forming bone > osteocytes

Question 27

osteocytes

Answer 27

• mature bone cells derived from osteoblasts that become trapped in lacunae of newly formed bone
• communicate + provide nutrients to one another via gap junctions in cytoplasmic processes, forming canaliculi

Question 28

osteoclasts

Answer 28

• break down/engulf bones during remodelling by releasing enzymes (destroy ECM) and acid (destroy mineralised bone)
• large cells w/ multiple nuclei (like macrophages)

Question 29

how are trabeculae arranged in spongy bone?

Answer 29

• along lines of compressive or tensile stress

Question 30

what develops from the embryonic ectoderm

Answer 30

• epidermis
• CNS and PNS

Question 31

what develops from the embryonic mesoderm

Answer 31

• dermis
• muscle
• blood vessels
• connective tissue
• serous membrane

Question 32

what develops from the embryonic endoderm

Answer 32

• epithelium
• GIT + liver
• respiratory tract