Lecture 6: Bone and Muscle Tissue Flashcards
What is bone tissue?
=> Specialized CT
→ Derived from mesenchyme of embryonic CT
What is the function of bones in the skeletal system:
Support
Movement
Protection
Mineral storage
Energy metabolism
Blood formation (HEMOPOIESIS)
What is the main structure of bones
Cells:
- Osteogenic
- Osteoblasts (immature, creating bone)
- Osteocytes (mature, maintaining bone)
- Osteoclasts
Extracellular Matrix
→ 90% collagen fibers → Mineral deposition in matrix leads to calcification
What are osteogenic cells?
Unspecialized stem cells which are first derived the mesenchyme tissue and located in the inner portion of the periosteum and endosteum
What are osteoblast cells?
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
What are osteocytes?
Mature cells that monito bone tissue,
Found in lacunae structures btw lamellae
Arranged in concentric circles called osteons
Pathways btw lacunnae called CANALLICULI
What are osteoclasts?
Fusion of monocytes of macrophages
Engulf bone tissue and return to blood stream (RESORBTION)
Attach to bone matrix
Use lysosomes to break down matrix
What are the two classifications for bone tissue?
→ Primary (immature, woven)
Secondary (mature lamellae) Collagen fibres arranged into osteons
How are bones supplied?
Each section of the bone ; metaphyseal, epiphysial, diaphyseal which each have their own vein artery and nerve.
Describe the bone structure of compact bone
OSTEONS (functional unit)
→Central Canal contains VAN
→ Lacuna (houses osteocytes)
Communication between osteons occur via Volkmann’s canal.
Label
What are the phases of bone formation before and after birth?
Before Birth
-
Intermembranous
- endochondral
After Birth:
Length
Width
*
Describe the process of intramembranous growth:
Development of the ossification centre → Calcification → Trabeculae forms (holes for VAN to fit in) → mesenchyme at peripheral end of bone develops periosteum
Describe the process of endochondral ossification?
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
Describe how bones grow in width:
Appositional Growth; Will grow on pre-existing surface of bone beneath periosteum .
Describe how bones grow in length?
Interstitial growth of cartilage: bone growth via formation of new cartilage within existing cartilage mass..
What are the zones of growth on the epiphyseal plates?
Zones of resting cartilage- PROXIMAL
Zones of proliferating cartilage
zones of hypertrophic cartilage
zone of calcified cartilage -DISTAL
What does Wolff’s Law state?
Bones in a healthy person or animal will adapt to the load its placed under
What is the function of muscle tissue?
Movement
stability
storage and transport of substances
heat production (BYPRODUCT OF KINETIC ENERGY)
How does motion occur?
The conversion of chemical ATP energy to mechanical energy by the contractile apparatus of muscle cells
What is the contractile apparatus of muscle tissues?
SARCOMERE!
composed of actin (THIN) and myosin (THICK) filaments arranged in the direction of contraction
What is a cytoplasm, plasma membrane, and smooth endoplasmic reticulum in terms of a myocell?
Cytoplasm: sarcoplasm
Plasma membrane; sarcolemma
Smooth endoplasmic reticulum ; sarcoplasmic reticulum {STORES AND RELEASES Ca)
What are the 3 types of muscle tissue?
- Skeletal- striated, voluntary,
-
Cardiac= striated, involuntary, intercalated discs
- Smooth= no striations, involuntary eg visceral organs
What nerve supply innervates skeletal muscles and how fascicles are organised?
SOMATIC NERVOUS SYSTEM
composed of fascicles which are bounded by connective tissue layers.
ENDOMYSIUM → MYOFIBRIL
PERIMYSIUM→ FASCICLE
EPIMYSIUM → WHOLE MUSCLE
Outline the organisation of muscles
myofilaments → Myofibrils → Myofibers → muscle fascicle → muscle
What are T-Tubules and identify their function
T-tubules are invaginations of the plasma membrane of myofibers which allows electrical impulses to travel deep into the myofilaments.
Describe the main features of the contractile apparatus of the sarcomere:
What are the 3 types of muscle fibers?
- Slow oxidative: Least powerful uses Aerobic cellular respiration (LONG DISTANCE RUNNING)
- Fast oxidative- glycolytic : aerobic and ANAEROBIC CELLULAR RESPIRATION →Fatigue quicker than type 1
- Fast glycolytic : mainly anaerobic cellular respiration (SPRINTING)
What are tendons made out of?
Dense regular connective CT; abundant collagen fibres
What is atrophy?
Muscular atrophy: decrease in myofibril
Disuse atrophy: Long term relaxation of muscle
Denervation atrophy: from disease eg motor neuron disease
What is an identifiable feature for cardiac muscles?
One muscle fibre; Mononuclear cell with a central nucleus and a large mitochondria
What is the function of the intercalated disks?
allows multiple cells to work together and the transmission of electrical impulses
