Lecture 6: Bone and Muscle Tissue

Question 1

What is bone tissue?

Answer 1

=> Specialized CT

→ Derived from mesenchyme of embryonic CT

Question 2

What is the function of bones in the skeletal system:

Answer 2

Support

Movement

Protection

Mineral storage

Energy metabolism

Blood formation (HEMOPOIESIS)

Question 3

What is the main structure of bones

Answer 3

Cells:

• Osteogenic
• Osteoblasts (immature, creating bone)
  
  • Osteocytes (mature, maintaining bone)
  • Osteoclasts

Extracellular Matrix

→ 90% collagen fibers → Mineral deposition in matrix leads to calcification

Question 4

What are osteogenic cells?

Answer 4

Unspecialized stem cells which are first derived the mesenchyme tissue and located in the inner portion of the periosteum and endosteum

Question 5

What are osteoblast cells?

Answer 5

Responsible for synthesis of organic components of matrix

Extract calcium from blood stream to deposit in bone

Present only on surface → WHEN SURROUNDED BY MATRIX WILL BECOME OSTEOCYTE

Question 6

What are osteocytes?

Answer 6

Mature cells that monito bone tissue,
Found in lacunae structures btw lamellae

Arranged in concentric circles called osteons

Pathways btw lacunnae called CANALLICULI

Question 7

What are osteoclasts?

Answer 7

Fusion of monocytes of macrophages

Engulf bone tissue and return to blood stream (RESORBTION)

Attach to bone matrix

Use lysosomes to break down matrix

Question 8

What are the two classifications for bone tissue?

Answer 8

→ Primary (immature, woven)

Secondary (mature lamellae) Collagen fibres arranged into osteons

Question 9

How are bones supplied?

Answer 9

Each section of the bone ; metaphyseal, epiphysial, diaphyseal which each have their own vein artery and nerve.

Question 10

Describe the bone structure of compact bone

Answer 10

OSTEONS (functional unit)

→Central Canal contains VAN

→ Lacuna (houses osteocytes)

Communication between osteons occur via Volkmann’s canal.

Question 11

Label

Answer 11

Question 12

What are the phases of bone formation before and after birth?

Answer 12

Before Birth

• Intermembranous
  
  • endochondral

After Birth:

Length

Width

*

Question 13

Describe the process of intramembranous growth:

Answer 13

Development of the ossification centre → Calcification → Trabeculae forms (holes for VAN to fit in) → mesenchyme at peripheral end of bone develops periosteum

Question 14

Describe the process of endochondral ossification?

Answer 14

Bone preceded by hyaline cartilage precursor

Primary ossification centre develops → Development of medullary cavity → Development of secondary ossification centre → formation of articular cartilage and epiphyseal plates

Question 15

Describe how bones grow in width:

Answer 15

Appositional Growth; Will grow on pre-existing surface of bone beneath periosteum .

Question 16

Describe how bones grow in length?

Answer 16

Interstitial growth of cartilage: bone growth via formation of new cartilage within existing cartilage mass..

Question 17

What are the zones of growth on the epiphyseal plates?

Answer 17

Zones of resting cartilage- PROXIMAL

Zones of proliferating cartilage

zones of hypertrophic cartilage

zone of calcified cartilage -DISTAL

Question 18

What does Wolff’s Law state?

Answer 18

Bones in a healthy person or animal will adapt to the load its placed under

Question 19

What is the function of muscle tissue?

Answer 19

Movement

stability

storage and transport of substances

heat production (BYPRODUCT OF KINETIC ENERGY)

Question 20

How does motion occur?

Answer 20

The conversion of chemical ATP energy to mechanical energy by the contractile apparatus of muscle cells

Question 21

What is the contractile apparatus of muscle tissues?

Answer 21

SARCOMERE!

composed of actin (THIN) and myosin (THICK) filaments arranged in the direction of contraction

Question 22

What is a cytoplasm, plasma membrane, and smooth endoplasmic reticulum in terms of a myocell?

Answer 22

Cytoplasm: sarcoplasm

Plasma membrane; sarcolemma

Smooth endoplasmic reticulum ; sarcoplasmic reticulum {STORES AND RELEASES Ca)

Question 23

What are the 3 types of muscle tissue?

Answer 23

• Skeletal- striated, voluntary,
• Cardiac= striated, involuntary, intercalated discs
  
  • Smooth= no striations, involuntary eg visceral organs

Question 24

What nerve supply innervates skeletal muscles and how fascicles are organised?

Answer 24

SOMATIC NERVOUS SYSTEM

composed of fascicles which are bounded by connective tissue layers.

ENDOMYSIUM → MYOFIBRIL

PERIMYSIUM→ FASCICLE

EPIMYSIUM → WHOLE MUSCLE

Question 25

Outline the organisation of muscles

Answer 25

myofilaments → Myofibrils → Myofibers → muscle fascicle → muscle

Question 26

What are T-Tubules and identify their function

Answer 26

T-tubules are invaginations of the plasma membrane of myofibers which allows electrical impulses to travel deep into the myofilaments.

Question 27

Describe the main features of the contractile apparatus of the sarcomere:

Answer 27

Question 28

What are the 3 types of muscle fibers?

Answer 28

1. Slow oxidative: Least powerful uses Aerobic cellular respiration (LONG DISTANCE RUNNING)
2. Fast oxidative- glycolytic : aerobic and ANAEROBIC CELLULAR RESPIRATION →Fatigue quicker than type 1
3. Fast glycolytic : mainly anaerobic cellular respiration (SPRINTING)

Question 29

What are tendons made out of?

Answer 29

Dense regular connective CT; abundant collagen fibres

Question 30

What is atrophy?

Answer 30

Muscular atrophy: decrease in myofibril

Disuse atrophy: Long term relaxation of muscle

Denervation atrophy: from disease eg motor neuron disease

Question 31

What is an identifiable feature for cardiac muscles?

Answer 31

One muscle fibre; Mononuclear cell with a central nucleus and a large mitochondria

Question 32

What is the function of the intercalated disks?

Answer 32

allows multiple cells to work together and the transmission of electrical impulses