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Skeletal system and tissues; Joints and skeletal muscle (Skeletal System…
Skeletal system and tissues;
Joints and skeletal muscle
Skeletal System and Tissues
Compact bone and spongy bone characteristics/features
Compact bone
Dense outer layer.
Spongy bone
Internal to compact bone. "Trabecular bone." Honeycomb of small flat pieces. Open spaces between the trabeculae are filled with red or yellow bone marrow
Components of a long bone
Epiphyseal line
Between the diaphysis and each epiphysis of an adult long bone. A remnant of the epiphyseal plate.
Compact bone
Dense outer layer.
Epiphysis
Bone ends. Joint surface of each epiphysis is covered with a thin layer of hyaline cartilage.
Spongy bone
Internal to compact bone. "Trabecular bone." Honeycomb of small flat pieces. Open spaces between the trabeculae are filled with red or yellow bone marrow.
Diaphysis
Shaft. Forms the long axis of a lone bone.
Medullary cavity
The very center of the diaphysis of long bones- contains no bone tissue. In adults, it is filled with yellow bone marrow.
Major structural components of the skeletal system
Cartilages
Elastic
Better able to tolerate repeated bending
Epiglottis
Outer ear
Fibrocartilage
Resists both strong compression and strong tension/pulling forces
Anulus fibrosus portion of discs between vertebrae
Articular discs of some joints e.g. the menisci of the knee
Hyaline
Provides support through flexibility and resilience
Attachment of ribs to sternum
Most of the cartilage in respiratory structures
Articular cartilage that covers the ends of adjoining bones in movable joints
Forms the embryonic skeleton
Ligaments
Connect bone to bone.
Bones
35% organic; 65% inorganic. Cells and extracellular matrix.
Short bone: Cube-like shape- e.g. carpals and tarsals.
Flat bone: Can be curved (frontal bone).
Long bone: Longer than it is wide
Irregular bone: oddly-shaped. Vertebrae.
Tendons
Connect bone to muscle.
Joints/Articulations
Where 2 bones meet for purpose of movement.
Red and yellow bone marrow
Red bone marrow- Gelatinous material. As an embryo/fetus, it fills all spaces inside bones (until about 7 years old). As adults, in vertebrae, coxal bones, sternum, ribs, and skull. Spongy bone is location of red bone marrow.
Yellow bone marrow- Nutrient storage (fat).
Major functions of the skeletal system
Protection
Vertabrae protects spinal cord
Rib cage protects organs of thorax
Skull protects brain
Mineral Storage
Calcium
Phosphate
Movement
Together with the muscular system
Blood cell formation
Red bone marrow
Support
Framework for connection of soft tissue
Tendons
Muscle to bone
Ligaments
Bone to bone
Energy Storage
Yellow bone marrow
Types of bone cells
Bone cells that produce or maintain the tissue
Osteoblasts
Osteogenic cells
Osteocytes
Bone cell responsible for resorption
Osteoclasts
Joints
Cartilaginous joints
Adjoining bones united by cartilage
Synchondrosis
Immobile
e.g. Epiphyseal plates, immovable joint between the 1st rib's costal cartilage and the manubrium of the sternum.
Hyaline cartilage
Symphysis
Fibrocartilage
Hyaline cartilage present in the form of articular cartilage
Slightly movable
e.g. Intervertebral discs, pubic symphysis of the pelvis
Synovial joint components
Synovial fluid
Slippery and lubricating. Shock absorption. Nourishes the articular cartilage.
Reinforcing ligaments
Some synovial joints are reinforced and strengthened by bandlike ligaments.
Articular capsule
2-layered
Outer: Fibrous layer of dense irregular connective tissue continuous with the periosteum layer of the joining bones. Strengthens the joint.
Inner: Synovial membrane composed of loose connective tissue. Lines the joint capsule and covers all the internal joint surfaces not covered by cartilage. Functions to make synovial fluid.
Nerves and vessels
Sensory nerve fibers that innervate the articular capsule. Detect pain and monitor stretching. Rich blood supply
Articular disc
Disc of fibrocartilage. Articular disc or "meniscus."
e.g. TMJ, sternoclavicular joint, knee joint.
Bursae and tendon sheaths
Contain synovial fluid. Reduce friction.
Bursa- Flattened fibrous sac lined by a synovial membrane.
Tendon sheath- Specialized type of bursa. Wraps around a tendon.
Joint (articular) cavity
A potential space that holds a small amount of synovial fluid.
Articular cartilage
Cover the ends of opposing bones- Composed of hyaline cartilage. Absorb compressive forces placed on the joint.
Fibrous joints
Adjoining bones united by collagenic fibers
Gomphosis
Periodontal ligament
Immobile..
Syndesmosis
Longer bundles of fibrous tissue (ligaments). Movement depends on length of fibers.
Slightly mobile (amphiarthrosis)
e.g.: Distal tibiofibular articulation
Immobile
e.g.: Interosseous membrane
Suture
Immobile (synarthrosis)
Location: Skull
Short, interconnecting fibers
Six structural types of synovial joints
(all are diarthroses / freely movable)
Hinge
Uniaxial movement- Flexion and extension.
Elbow joints, interphalangeal joints.
Pivot
Uniaxial movement- Rotation.
Proximal radioulnar joints, atlantoaxial joint.
Plane
Nonaxial movement: Gliding.
Intercarpal joints, intertarsal joints, joints between vertebral articular surfaces.
Condylar
Biaxial movement- Adduction and abduction; Flexion and extension.
Metacarpophalangeal (knuckle) joints, wrist joints.
Saddle
Biaxial movement- Adduction and abduction; Flexion and extension.
Carpometacarpal joints of the thumbs
Ball-and-socket
Multiaxial movement. Flexion and extension; Adduction and abduction; Rotation.
Shoulder joints and hip joints.
Skeletal muscle
Connective tissue layers
Perimysium
Covers each fascicle (group). Fibrous connective tissue.
Epimysium
An outer layer of dense irregular connective tissue surrounds the whole skeletal muscle (binds it together).
Endomysium
Within a fascicle, each muscle fiber is surrounded by endomysium. Composed of loose connective tissue: Mostly reticular fibers. Allows space for very small blood vessels to run next to muscle fibers.
Deep Fascia
Binds whole muscles together. Dense irregular connective tissue.
Components of a skeletal fiber
Transverse (T) tubules
Deep invaginations of the sarcolemma that run between each pair of terminal cisterns.
Mitochondria
Supply energy for muscle contraction.
Sarcoplasmic reticulum
Smooth endoplasmic reticulum- Storage of calcium.
Sarcolemma
The plasma membrane.
Myofibrils
Smaller than muscle fibers. Cylinder-shaped organelles with striations. Main component of the sarcoplasm. Composed of sarcomeres arranged end-to-end.
Other microscopic skeletal muscle components
I-band
LIGHT. Thin filaments only. 2 regions on either side of the A-band.
H-zone
Central part of an A-band, where no thin filaments reach. Thick filaments only.
A-Band
Thick and thin filaments overlap. DARK.
Z-disc (line)
Boundaries of sarcomere. Actin is attached.
M-line
Thick filaments linked by accessory proteins.
Sarcomere- Unit of contraction. Composed of myofilaments made up of contractile proteins.
Thin filaments made of actin protein
Thick filaments made of myosin protein with myosin heads
Properties
Excitability
The ability to respond to stimulus. Nerve signals or other stimuli excite muscle cells; this causes electrical impulses to travel along the cell's plasma membrane.
Extensibility
Ability to stretch (within limits).
Contractility
Generate tension or force when pulling on an attachment point. 2 kinds of myofilaments.
Actin
Myosin
Elasticity
Ability to return to original shape after contraction/extension.
Functions
Maintain posture and stabilize joints
Skeletal muscles continuously contract to maintain posture. Muscle tone is a constant, low-level contraction of muscles that helps stabilize and strengthen many synovial joints.
Generate heat
Muscle contraction produces heat.
Open and close body passageways
Sphincter muscles function as valves.
Produce movement
Contents of hollow organs
Blood
Bones