Muscles and Skeletal Flashcards
What is a skeletal muscle made up of?
Skeletal muscles are made up of muscle fibres, which are made up of myofibrils.
Myofibril is composed of overlapping strands of contractile protein called myosin and thinner protein strands called actin.
Each contractile protein is known as a sarcomere.
Explain the structure of the muscle.
A band (centre of the sarcomere) - a dark region where the myosin and actin filaments overlap.
I band - lighter bands between the dark bands in which only actin is present.
H zone - region within each A band in which only myosin is present
Z line - marks the end of the sarcomere and the beginning of the next
What makes up actin?
Actin filaments also contain two other proteins known as troponin and tropomyosin, which are involved in the mechanism of muscle contraction.
Explain the sliding filament theory.
Calcium is released and binds with troponin, altering its shape. It is now able to displace tropomyosin, which blocks the myosin and actin binding. This enables myosin heads to attach to the actin filaments. As the myosin heads to attach to the actin binding sites, they tilt and the actin to slide past. As thy move, the myosin heads become detached and then bind to the next binding site.
What are the four types of bone cells?
Osteoprogenitor - undifferentiated cells (pre osteoblast)
Osteoblasts - form matrix and collagen fibres but can’t divide (bone forming)
Osteocytes - principal cells of bone tissue, mature cells (inactive osteoblasts)
Osteoclasts - serve to break down bone tissue (bone reabsorbing)
Explain the microscopic structure of compact bone.
Made up of osteons or Haversian systems. Osteons are made up of concentric layers called lamellae. In the centre of the osteons are central canals that contain blood and lymphatic vessels and nerves. Branching of the central canals are Volkmann’s canals which run the nerves to the periosteum. Within the lamellae are the lacunae which are small spaces, which has canaliculi containing osteocytes.
What is cartilage and what does it consist of?
Cartilage is a connective tissue.
It consists of a firm no cellular matrix called chondrin. Embedded in the chondrin are collagen fibres. The cellular component of cartilage are mature chrondrocytes. Cartilage begins with immature cartilage cells caked chondroblasts. They gradually become surrounded by matrix and trapped within the lacunae.
Describe hyaline cartilage
- Cartilage contains many closely packed collagen fibres throughout the matrix.
- Collagen fibres are extremely fine.
- They give strength and flexibility.
- Found in trachea, bronchi and at the ends of bones (articulate cartilage)
Describe elastic cartilage
- Contains collagen fibres similar to those in hyaline cartilage but they are not so closely packed together.
- Many conspicuous elastic fibres
- Provides flexible elastic support
- Found in external ear, nose
Describe fibrocartilage
- Has a course appearance from the thick collagen fibres arranged in bundles.
- Collagen fibres are not as compacted as hyaline cartilage, so can be compressed slightly,
- Found in parts of the body where the weight of the body is being supported (intervertebral discs, articulated discs, synovial joints).
What are the three categories of joints?
Fixed joints - allow little or no movement of the bones
Slightly moveable joints - allow the bones a small degree of movement.
Synovial joints - designed to lubricate and cushion the bones of the joint so they can move freely.
What are the types of synovial joints?
Ball and socket joint - hip and femur Hinge joint - elbow and knee Gliding joint - vertebrae Saddle joint - thumb Pivot joint - cervical vertebrae and neck Ovoid joint - wrist
