Connective Tissue

Question 1

What are some common features of connective tissues:?

Answer 1

1. few cells (“hole” in ECM - lacuna)
2. mostly ECM

Question 2

What makes up the Extracellular Matrix (ECM)?

Answer 2

1. ground substance
2. protein fibers

Question 3

What are the 3 types of protein fibers found in ECM?

Answer 3

1. collagen (most common)
2. elastic
3. reticular

Question 4

What determines the properties of the ECM and examples of this?

Answer 4

proportions
1. hard - calcified in bone
2. gel-like - loose connective in cartilage
3. fluid - in blood

(properties vary on how much you have of each protein fiber - bone vs ear)

Question 5

Collagen fiber features:

Answer 5

• high tensile strength
• flexible
• like a rope

Question 6

Elastic fiber features:

Answer 6

• low tensile strength
• recoils
• like a rubber band

Question 7

What is the most abundant protein in the body?

Answer 7

collagen

Question 8

What is the structure of collagen

Answer 8

triple helix structure (long thick rods)

Question 9

How to build collagen?

Answer 9

chain -> triple helix -> colalgen fiber -> collagen fibril

1. one polypeptide chain (primary)
2. 3 chains into triple stranded collagen (triple helix)
3. many triple helix come together to make a collagen fiber
4. collagen fibril - lots of collagen fibers

Question 10

What is ground substance made of?

Answer 10

proteoglycan molecules with glycosaminoglycan (GAG) chains (like bristles)

Question 11

Why are you 1 cm taller in the morning than in the evening?

Answer 11

The negative charge of GAG chains in cartilage reacts with water and absorbs it throughout the night. As you walk around the water gets squeezed out and you get shorter.

Question 12

Function of water in cartilage:

Answer 12

1. add firmness to ground substance
2. contribute to joint lubrication

Question 13

What are two specialized cells found in cartilage?

Answer 13

1. fibroblasts
2. macrophages

Question 14

What do fibroblasts do?

Answer 14

synthesis collagen & elastin fibers - secrete hyaluronic acid

Question 15

What do macrophages do?

Answer 15

engulf damaged cells & pathogens

Question 16

What are the non-universal categories of cartilage?

Answer 16

1. General - loose & fibrous
2. Specific - cartilage, bone, blood, hemopoietic tissue

Question 17

What are the three types of loose connective tissue?

Answer 17

1. mesenchyme
2. adipose tissue
3. areolar tissue

Question 18

What is mesenchyme tissue?

Answer 18

embryonic tissue
- gives rise to all other connective tissue
- mesenchymal cells (but no tissue) in adults

Question 19

What is adipose tissue?

Answer 19

store fat
- energy storage, padding, insulation

Question 20

What are the two types of adipose tissue and their functions/locations?

Answer 20

1. energetic white fat (typical- belly, hypodermis)
2. thermogenic brown fat (catabolism gives off heat - babies with small surface area to volume)

Question 21

What is areolar tissue?

Answer 21

“packing peanuts”
- cushion & support organs, nerves
- lots of collagen & elastin fibers
- in papillary layers of dermis

Question 22

What are the 2 types of fibrous connective tissue?

Answer 22

1. dense regular - parallel collagen fibers
2. dense irregular - strength and support from multiple directions

Question 23

What are three examples of dense regular connective tissues?

Answer 23

1. aponeuroses
2. ligaments (bone to bone - plywood)
3. tendons (muscle to bone - rope)

Question 24

What are two examples of dense irregular connective tissues?

Answer 24

1. periosteum (around the bone)
2. reticular layer (suede inside of leather)

Question 25

What are the 3 types of cartilage?

Answer 25

1. hyaline cartilage 2. elastic cartilage 3. fibrocartilage

Question 26

What are some locations of the 3 cartilage types?

Answer 26

1. hyaline - ribs, joints of limbs, hip, nose 2. elastic - ears, epiglottis 3. fibro - spine discs, knees, pubic symphysis

Question 27

Describe hyaline cartilage

Answer 27

- most common cartilage - relatively weak - forms embryonic skeleton (fontanelles)

Question 28

Describe elastic cartilage

Answer 28

- elastic fiber is flexible & resilient - weakest - least common cartilage

Question 29

Describe fibrocartilage

Answer 29

- in areas of high stress. - strongest - lots of collagen & little ground substance

Question 30

What are some of the main structures of bone? (6)

Answer 30

1. Osteon made of 2. Concentric lamella which have 3. Osteocytes in 4. Lacuna with 5. Canalculi coming off 6. Central/Haversian canal going through middle

Question 31

What are the characteristics of bone tissue?

Answer 31

- few osteocytes - mostly hard, calcified matrix

Question 32

What are the components of the calcified matrix of bone?

Answer 32

- bone is a composite tissue 1. collagen - 1/3 - adds flexibility 2. CaPO4 & CaCO3 - 2/3 - hard, but brittle

Question 33

What is the structure of bone matrix?

Answer 33

CaPO4 as crystals of hydroxyapatite and CaCO3 bound to collagen triple helix

Question 34

What are the types of bone cells? (3)

Answer 34

1. osteoblasts 2. osteocytes 3. osteoclasts

Question 35

Describe osteoblasts

Answer 35

builds bone tissue matrix - get trapped in matrix (lacuna) become osteocyte

Question 36

Describe osteocytes

Answer 36

mature cell which maintains matrix

Question 37

Describe osteoclasts

Answer 37

break down bone matrix to be recycled - use HCL & lysosomes

Question 38

Why is the directionality of collagen fibers different between lamellae?

Answer 38

to prevent microwear and tear so it won't continue all the way through osteon (like cracks in concrete)

Question 39

What connects central canals of one osteon to another?

Answer 39

Volkmann's canals

Question 40

How does bone resist fracturing?

Answer 40

1. bone is a composite material (collagen & CaPO4) 2. collagen orientation changes (directionality of collagen fibers)