Histology

Endochondral ossification.

They act as stretch receptors, monitoring muscle length.

By the fusion of myoblasts.

Skeletal muscle fibers are formed by the fusion of muscle cells called myoblasts.

They are fast glycolytic, large fibers with fewer mitochondria, high anaerobic enzyme activity, and fatigue rapidly.

Contraction is slow and sustained.

An action potential in the neuron releases neurotransmitter.

Hematoma formation around the fracture.

They activate and help regenerate damaged muscle fibers after injury.

Epimysium, perimysium, and endomysium.

1:12.

It is a remnant of hyaline cartilage without perichondrium.

Troponin binds to calcium and regulates the interaction between actin and myosin.

They slide along actin and create muscle tension.

TNAP, osteocalcin, and osteoprotegerin.

Skeletal muscle is a syncytium and multinucleated.

In intervertebral discs, pubic symphysis, menisci of the knee, and the temporomandibular joint.

They are actin-binding proteins that block the myosin binding site.

Fibroblasts in the perichondrium differentiate into chondrocytes, secreting new matrix.

Flat chondrocytes surrounded by parallel collagen type II fibers.

Due to lack of vascularity.

The regulatory light chain.

It forms an elastic lattice that anchors thick filaments to the Z discs.

Osteoblasts, under the influence of BMPs and other factors.

The SOX9 gene.

A homogeneous, amorphous matrix.

Fascia adherens, maculae adherens (desmosomes), and gap junctions.

They secrete the cartilage matrix and are found in lacunae.

Elongated, fusiform cells with centrally located nuclei, involuntary contractions, and not striated.

Injury.

A longitudinal layer that runs parallel to the organ's long axis and a circular layer that runs along the circumference.

Osteoadherin binds strongly to hydroxyapatite crystals, aiding in bone stabilization.

Osteoprogenitor cells differentiate into osteoblasts, laying down matrix (osteoid) on the spicule framework.

Haversian systems (osteons) consisting of concentric lamellae surrounding a central canal.

A disease of the neuromuscular junction associated with muscle weakness.

Multi Adhesive proteins like fibronectin, anchoring, tenascin, and collagen type VI.

Atrial natriuretic factor and brain natriuretic factor; they are diuretics affecting sodium excretion.

It anchors cartilage to subchondral bone and leaves a line called the tidemark.

A bands, which are birefringent and alter polarized light.

An increase in Ca concentration inside the cell.

Osteoblasts release matrix vesicles that facilitate the formation of hydroxyapatite from calcium and phosphate.

The ruffled border increases the cell's surface area for the secretion of acids and enzymes necessary for bone resorption.

They shorten, while the A band remains the same length.

The actin is slid towards the M line with the release of a phosphate group.

Calcium entry triggers synaptic vesicles to release acetylcholine (Ach).

It degrades acetylcholine, ending the depolarization signal to the muscle cell.

They regulate phosphate levels and are involved in mechanotransduction and osteocytic osteolysis.

In the fetal skeleton, trachea, larynx, nose, bronchi, ribcage, and articulating surfaces of bones.

They are branched, contain intercalated discs, and have striations.

Rich collagen types I and II.

Thick filaments have 2 heavy chains and 4 light chains, oriented in one direction on one side and in the opposite direction on the other side, with asymmetrically tapered bare ends.

Chondrocytes divide within lacunae, expanding the cartilage from within as they secrete a new matrix.

Thick filaments contain myosin 2 molecules arranged in an antiparallel fashion along with associated proteins.

Chondrocytes secrete matrix, which begins to calcify, leading to cell death due to restricted nutrient diffusion.

M line proteins.

It has a high cell-to-matrix ratio and is typically found in the fetal skeleton.

Intercalated discs.

Diad.

They help ensure a normal heartbeat and are involved in arrhythmias and ventricular remodeling.

Acts as a shock absorber.

Z lines.

Osteoclasts are large, multinucleated cells that resorb bone by secreting enzymes and acids that dissolve hydroxyapatite.

The outer bone is compact, while the inner bone is trabecular (spongy), filled with marrow and blood vessels.

Zone of reserve cartilage, zone of proliferation, zone of hypertrophy, zone of calcification, zone of ossification.

Osteoclasts release calcium, phosphate, and growth factors stored in the bone matrix into the bloodstream.

It serves as a Ca²⁺ ion reservoir and releases calcium during contraction.

Acetylcholine (ACh).

They resorb bone, creating a resorption cavity.

Modified muscle fibers within muscle spindles that detect stretch.

Calcium induced calcium release (CICR).

They are slow oxidative, generate great resistance to fatigue, and are useful for long endurance activities.

The presence of elastin and collagen type II.

The bone matrix is composed of 90% Type I and V collagen and 10% ground substance, including proteoglycans and glycoproteins.

PTH stimulates osteoclast activity indirectly via osteoblasts, while calcitonin inhibits bone resorption by suppressing osteoclast activity.

The release of Ca²⁺ from the sarcoplasmic reticulum upon an action potential.

Mitochondria, Golgi apparatus, lipofuscin granules, and glycogen.

Limited repair capacity but shows no signs of abrasive wear over time.

Perichondrium.

It contains perpendicular collagen fibers.

In the external ear, wall of the external acoustic meatus, epiglottis, and auditory tube.

It protects the myosin binding site on actin in resting muscle.

Cells observed in the resorbed articular cartilage of joint diseases like rheumatoid arthritis; they may be mature osteoclasts.

One for ATP with ATPase activity and one for actin.

Connective tissue holds muscle fibers together.

They are fast oxidative and glycolytic, capable of anaerobic glycolysis, and generate high peak muscle tension.

The sarcomere.

A condition associated with joint pain, deformity, and destruction of the articular cartilage.

It phosphorylates the light chain in myosin heads, increasing myosin ATPase activity.

OPG acts as a decoy receptor for RANKL, regulating bone resorption by preventing further activation of osteoclasts.

BFA-1, RUNX2, IGF-1, and BMPs.

Signals from PAX3 and PAX7.

Subunits TnT and TnI of the cardiac troponin complex.

Actin, tropomyosin, caldesmon, and calponin.

Structures that link thin and intermediate filaments to the cell membrane.

Four distinct zones.

It activates myosin light chain kinase.

Osteoclasts create Howship's lacunae, which are later filled by osteoblasts with new bone.

The interaction between heavy and light chains of myosin.

A motor neuron and the muscle fibers it supplies.

Elevated levels of SOX9, collagen types II and X, and aggrecan in biopsies.

Cartilage model formation from mesenchymal cells differentiating into chondroblasts.

It allows for synchronous contraction of all sarcomeres in the myofibril.

A complex of a T tubule and two adjacent terminal cisternae.

They bind ACh, causing depolarization of the postsynaptic membrane.

the superficial zone : flat chondrocytes surrounded by parallel collagen type 2 fibers

the middle transitional zone : round chodnrocytes with a high concentration of proteoglycans

the deep radial zone : perpendicular to collagen fibers

the calcified zone : anchord cartilage to the subchondral bone leaving behind a line called th etidemark