Muscoskeletal System Flashcards
Types of muscles
- Skeletal muscle
- Smooth muscle
- Cardiac muscle
Skeletal muscle functions
- Support body
- Allow movement
- Compress venous structures to propel blood and lymph
- Shivering
Skeletal muscle features
- Striated due to sarcomeres
- Multinucleated
- Has red and white fibers
Red fibers
Slow-twitch.
- High myoglobin content (aerobic)
- Mostly in muscles that contract slowly but sustain activity
White fibers
Fast-twitch.
- Less myoglobin, so lighter in color
- Less mitochondria, rely more on glycolysis
- Mostly in muscles that contract fast, but fatigues easily
Smooth muscle functions
- Involuntary movement
2. Regulation of BP
Smooth muscle features
- Single nucleus in center of cell
- Contain actin and myosin, but not well-organized
- Capable of more sustained contractions
Tonus
Constant state of low-level contraction
Myogenic activity
Contraction of smooth or cardiac muscle without nervous system input.
Cardiac muscle features
- Primarily uninucleated, but many do contain 2
- Involuntary, but appears striated
- Connected by intercalated discs that have many gap junctions
- Relies on calcium for contraction
Sarcomere
Thick and thin filaments
- Z-line
- M-line
- I-band
- H-zone
- A-band
During contraction, what lines decrease and what stays constant
- H-zone, I-band, distance between Z-lines, and distance between M-lines become smaller
- A-band size remains constant
Myofibrils
Back-to-back sarcomeres attached to one another
Sarcoplasmic reticulum
Modified ER that has a high calcium concentration that surrounds myofibrils
Sarcoplasm
Modified cytoplasm of myocyte
Sarcolemma
Cell membrane. Can propagate action potential using transverse (T) tubules
Myocyte
contains many myofibrils arranged in parallel (muscle fibers). Numerous nuclei
Muscle
Many myocytes in parallel
Muscle contraction
- Start: neuromuscular junction, nervous system communicate via efferent neurons
- Travel down neuron until nerve terminal, ACh released into synapse
- Depolarization down sarcolemma to T-tubules
- When action potential reaches SR, Ca released
, which binds to troponin triggering changes in tropomyosin. - Free globular heads of myosin binds to exposed sites on actin
- Relaxation by ACh degradation
Role of ATP in muscle contraction
- Myosin carrying ADP + Pi bound to myosin-binding site after calcium trigger in tropomyosin structure
- ATP binds to myosin head, the hydrolysis into ADP releases myosin from actin
Skeletal structure
- Axial: basic central framework - skull, vertebral column, ribcage, hyoid bone
- Appendcular skeleton: limbs, pectoral girdle, pelvis
Hyoid bone
In anterior neck, used for swallowing
Bone composition
- Compact bone: dense and strong
2. Spongy (cancellous) bone: spongy
Spongy bones
- Trabeculae: bony spicules (points)
- Bone marrow: fills cavities between trabeculae
- Long bones
Bone marrow types
- Red marrow: filled with hematopoietic stem cells
2. Yellow marrow: fat and relatively inactive
Long bones
- cylindrical shafts (diaphyses), then metaphysis, end with epiphysis
- Outer part: compact, inner part : spongy
Periosteum
Fibrous sheath that surrounds long bone to protect it and serve as site of muscle attachment. Need to be healthy for bone marrow
Tendons vs. Ligaments
- Tendons: muscle to bone
2. Ligaments: bone to bone
Review microscopic bone structure
Harvesian canal, lacunae and osteocyte, cannaculi, periosteum, volkmann’s canal, ostean
Bone matrix: organic components
- Collagen
- Glycoproteins
- Other peptides
Bone matrix: inorganic components
They harden together to form hydroxypatite crystals
- Calcium
- Phosphate
- Hydroxide ions
Osteons/haversian systems
Structures of bony matrix of organic and inorganic components.
Lacunae
House osteocytes
Canaliculi
Allow exchange of nutrients and wastes between osteocytes, Haversian, and Volkmann’s canals
Osteoclasts
- Macrophages of bone that reabsorb it.
2. Polynucleated
Chondrin
elastic, firm matrix
Cartilage
- Softer, more flexible than bone
2. Avascular (no blood and lymphatic vessels), not innervated
Endochondral ossification
hardening of cartilage into bone
Intramembraneous ossification
Undifferentiated mesenchymal tissue transformed into bone. In bones of skull
Mesenchymal tissue
embryonic connective tissue
Synovial capsule
enclose joint cavity (arituclar cavity)
Synovium
layer of soft tissue, secrete synovial fluid that lubricate movement in joints
Articular cartilage
Coats articular surfaces of the bone so that impact is restricted to lubricated joint cartilage
