What is the process that replaces the soft callus with a hard callus?
Endochondral ossification.
p.7
Muscle Contraction Mechanisms
What is the function of muscle spindles?
They act as stretch receptors, monitoring muscle length.
p.7
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
How are muscle fibers formed during development?
By the fusion of myoblasts.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What forms skeletal muscle fibers?
Skeletal muscle fibers are formed by the fusion of muscle cells called myoblasts.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are the characteristics of Type-2b muscle fibers?
They are fast glycolytic, large fibers with fewer mitochondria, high anaerobic enzyme activity, and fatigue rapidly.
p.9
Muscle Contraction Mechanisms
What is the contraction speed and nature of smooth muscle?
Contraction is slow and sustained.
p.7
Muscle Contraction Mechanisms
What triggers the contraction of a muscle fiber?
An action potential in the neuron releases neurotransmitter.
What initiates the inflammatory response following a bone injury?
Hematoma formation around the fracture.
p.7
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the role of satellite cells in muscle regeneration?
They activate and help regenerate damaged muscle fibers after injury.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are the three layers of connective tissue surrounding muscle fibers?
Epimysium, perimysium, and endomysium.
p.1
Articular Cartilage Structure and Function
What is a key feature of articular cartilage?
It is a remnant of hyaline cartilage without perichondrium.
p.5
Muscle Contraction Mechanisms
What role does troponin play in muscle contraction?
Troponin binds to calcium and regulates the interaction between actin and myosin.
p.9
Muscle Contraction Mechanisms
What do active myosin cross bridges do during contraction?
They slide along actin and create muscle tension.
What do osteoblasts secrete to regulate bone resorption?
TNAP, osteocalcin, and osteoprotegerin.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the structural characteristic of skeletal muscle?
Skeletal muscle is a syncytium and multinucleated.
p.1
Fibrous Cartilage Functions and Locations
Where is fibrous cartilage found?
In intervertebral discs, pubic symphysis, menisci of the knee, and the temporomandibular joint.
p.9
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the role of caldesmon and calponin in smooth muscle?
They are actin-binding proteins that block the myosin binding site.
p.2
Cartilage Development and Types
What is appositional growth in cartilage?
Fibroblasts in the perichondrium differentiate into chondrocytes, secreting new matrix.
p.1
Articular Cartilage Structure and Function
What characterizes the superficial zone of articular cartilage?
Flat chondrocytes surrounded by parallel collagen type II fibers.
p.2
Hyaline Cartilage Characteristics
Why does hyaline cartilage have limited repair ability?
Due to lack of vascularity.
p.6
Muscle Contraction Mechanisms
What stabilizes the lever arm of myosin?
The regulatory light chain.
p.6
Muscle Contraction Mechanisms
What is the role of titin in muscle structure?
It forms an elastic lattice that anchors thick filaments to the Z discs.
p.3
Bone Formation Processes: Endochondral and Intramembranous Ossification
What do mesenchymal cells differentiate into during intramembranous ossification?
Osteoblasts, under the influence of BMPs and other factors.
p.1
Hyaline Cartilage Characteristics
What characterizes hyaline cartilage?
A homogeneous, amorphous matrix.
p.8
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are the three types of cell-cell junctions found in intercalated discs?
Fascia adherens, maculae adherens (desmosomes), and gap junctions.
p.1
Hyaline Cartilage Characteristics
What is the role of chondrocytes in cartilage?
They secrete the cartilage matrix and are found in lacunae.
What are the characteristics of smooth muscle cells?
Elongated, fusiform cells with centrally located nuclei, involuntary contractions, and not striated.
p.9
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What layers do smooth muscle form in the walls of hollow organs?
A longitudinal layer that runs parallel to the organ's long axis and a circular layer that runs along the circumference.
p.4
Bone Structure and Remodeling
What role does osteoadherin play in bone?
Osteoadherin binds strongly to hydroxyapatite crystals, aiding in bone stabilization.
p.2
Bone Formation Processes: Endochondral and Intramembranous Ossification
What forms the primary ossification center?
Osteoprogenitor cells differentiate into osteoblasts, laying down matrix (osteoid) on the spicule framework.
p.3
Bone Structure and Remodeling
What structures are organized in mature bone?
Haversian systems (osteons) consisting of concentric lamellae surrounding a central canal.
p.7
Neuromuscular Junction and Muscle Innervation
What is myasthenia gravis?
A disease of the neuromuscular junction associated with muscle weakness.
p.1
Hyaline Cartilage Characteristics
What types of proteins are found in the matrix of hyaline cartilage?
Multi Adhesive proteins like fibronectin, anchoring, tenascin, and collagen type VI.
p.8
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What hormones are contained in atrial granules and what is their function?
Atrial natriuretic factor and brain natriuretic factor; they are diuretics affecting sodium excretion.
p.2
Articular Cartilage Structure and Function
What is the function of the calcified zone in cartilage?
It anchors cartilage to subchondral bone and leaves a line called the tidemark.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are the dark bands in a sarcomere called?
A bands, which are birefringent and alter polarized light.
p.9
Muscle Contraction Mechanisms
What initiates smooth muscle contraction?
An increase in Ca concentration inside the cell.
p.4
Bone Formation Processes: Endochondral and Intramembranous Ossification
How do osteoblasts contribute to hydroxyapatite crystal formation?
Osteoblasts release matrix vesicles that facilitate the formation of hydroxyapatite from calcium and phosphate.
p.4
Bone Structure and Remodeling
What is the significance of the ruffled border in osteoclasts?
The ruffled border increases the cell's surface area for the secretion of acids and enzymes necessary for bone resorption.
p.6
Muscle Contraction Mechanisms
What happens to the sarcomere and I band during muscle contraction?
They shorten, while the A band remains the same length.
p.6
Muscle Contraction Mechanisms
What occurs during the power stroke of muscle contraction?
The actin is slid towards the M line with the release of a phosphate group.
p.7
Muscle Contraction Mechanisms
What role does calcium play in muscle contraction?
Calcium entry triggers synaptic vesicles to release acetylcholine (Ach).
p.7
Neuromuscular Junction and Muscle Innervation
What is the function of acetylcholinesterase at the neuromuscular junction?
It degrades acetylcholine, ending the depolarization signal to the muscle cell.
What is the function of osteocytes in bone tissue?
They regulate phosphate levels and are involved in mechanotransduction and osteocytic osteolysis.
p.1
Hyaline Cartilage Characteristics
Where is hyaline cartilage found?
In the fetal skeleton, trachea, larynx, nose, bronchi, ribcage, and articulating surfaces of bones.
p.7
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are the characteristics of cardiac muscle fibers?
They are branched, contain intercalated discs, and have striations.
p.1
Fibrous Cartilage Functions and Locations
What provides fibrous cartilage with high tensile strength?
Rich collagen types I and II.
p.9
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
How does the structure of thick filaments in smooth muscle differ from skeletal muscle?
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.
p.2
Cartilage Development and Types
How does interstitial growth occur in cartilage?
Chondrocytes divide within lacunae, expanding the cartilage from within as they secrete a new matrix.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the composition of thick filaments in muscle fibers?
Thick filaments contain myosin 2 molecules arranged in an antiparallel fashion along with associated proteins.
p.2
Bone Formation Processes: Endochondral and Intramembranous Ossification
What happens during matrix calcification in endochondral ossification?
Chondrocytes secrete matrix, which begins to calcify, leading to cell death due to restricted nutrient diffusion.
p.3
Bone Structure and Remodeling
What is the primary characteristic of immature bone (woven bone)?
It has a high cell-to-matrix ratio and is typically found in the fetal skeleton.
p.8
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What role do cardiac macrophages play in heart function?
They help ensure a normal heartbeat and are involved in arrhythmias and ventricular remodeling.
p.1
Fibrous Cartilage Functions and Locations
What is the primary function of fibrous cartilage?
Acts as a shock absorber.
p.4
Bone Structure and Remodeling
What are osteoclasts and their primary function?
Osteoclasts are large, multinucleated cells that resorb bone by secreting enzymes and acids that dissolve hydroxyapatite.
p.4
Bone Structure and Remodeling
What are the two types of bone structure?
The outer bone is compact, while the inner bone is trabecular (spongy), filled with marrow and blood vessels.
p.2
Bone Formation Processes: Endochondral and Intramembranous Ossification
What are the zones of the epiphyseal growth plate?
Zone of reserve cartilage, zone of proliferation, zone of hypertrophy, zone of calcification, zone of ossification.
p.4
Bone Structure and Remodeling
What do osteoclasts release during bone resorption?
Osteoclasts release calcium, phosphate, and growth factors stored in the bone matrix into the bloodstream.
p.6
Muscle Contraction Mechanisms
What is the function of the sarcoplasmic reticulum in muscle contraction?
It serves as a Ca²⁺ ion reservoir and releases calcium during contraction.
p.3
Bone Structure and Remodeling
What role do osteoclasts play in bone remodeling?
They resorb bone, creating a resorption cavity.
p.7
Muscle Contraction Mechanisms
What are intrafusal fibers?
Modified muscle fibers within muscle spindles that detect stretch.
p.8
Muscle Contraction Mechanisms
What phenomenon is crucial for excitation-contraction coupling in cardiac muscle?
Calcium induced calcium release (CICR).
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What are Type-1 muscle fibers known for?
They are slow oxidative, generate great resistance to fatigue, and are useful for long endurance activities.
p.1
Elastic Cartilage Properties
What gives elastic cartilage its high pliability?
The presence of elastin and collagen type II.
p.4
Bone Structure and Remodeling
What is the composition of the bone matrix?
The bone matrix is composed of 90% Type I and V collagen and 10% ground substance, including proteoglycans and glycoproteins.
p.4
Bone Structure and Remodeling
What is the role of PTH and calcitonin in bone metabolism?
PTH stimulates osteoclast activity indirectly via osteoblasts, while calcitonin inhibits bone resorption by suppressing osteoclast activity.
p.6
Muscle Contraction Mechanisms
What initiates the muscle contraction process?
The release of Ca²⁺ from the sarcoplasmic reticulum upon an action potential.
p.8
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the juxtanuclear region in cardiac muscle cells rich in?
Mitochondria, Golgi apparatus, lipofuscin granules, and glycogen.
p.1
Hyaline Cartilage Characteristics
What is the repair capacity of hyaline cartilage?
Limited repair capacity but shows no signs of abrasive wear over time.
p.2
Articular Cartilage Structure and Function
What characterizes the deep (radial) zone of cartilage?
It contains perpendicular collagen fibers.
p.1
Elastic Cartilage Properties
Where is elastic cartilage located?
In the external ear, wall of the external acoustic meatus, epiglottis, and auditory tube.
p.5
Muscle Contraction Mechanisms
What is the function of tropomyosin in muscle contraction?
It protects the myosin binding site on actin in resting muscle.
What are chondroclasts and where are they observed?
Cells observed in the resorbed articular cartilage of joint diseases like rheumatoid arthritis; they may be mature osteoclasts.
p.6
Muscle Contraction Mechanisms
What are the two specific binding sites on the myosin head?
One for ATP with ATPase activity and one for actin.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What is the role of connective tissue in skeletal muscle?
Connective tissue holds muscle fibers together.
p.5
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What distinguishes Type-2a muscle fibers?
They are fast oxidative and glycolytic, capable of anaerobic glycolysis, and generate high peak muscle tension.
What is osteoarthritis?
A condition associated with joint pain, deformity, and destruction of the articular cartilage.
p.9
Muscle Contraction Mechanisms
What happens after myosin light chain kinase is activated?
It phosphorylates the light chain in myosin heads, increasing myosin ATPase activity.
p.4
Bone Structure and Remodeling
What is the function of osteoprotegerin (OPG) in bone remodeling?
OPG acts as a decoy receptor for RANKL, regulating bone resorption by preventing further activation of osteoclasts.
p.3
Bone Formation Processes: Endochondral and Intramembranous Ossification
What factors influence mesenchymal cells to differentiate into osteoprogenitor cells?
BFA-1, RUNX2, IGF-1, and BMPs.
p.7
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What initiates the differentiation of mesodermal progenitor cells into myoblasts?
Signals from PAX3 and PAX7.
p.8
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What markers are used to confirm myocardial infarction (MI) in blood tests?
Subunits TnT and TnI of the cardiac troponin complex.
p.9
Muscle Histology: Skeletal, Cardiac, and Smooth Muscle
What proteins are found in the thin filaments of smooth muscle?
Actin, tropomyosin, caldesmon, and calponin.
What are dense bodies in smooth muscle cells?
Structures that link thin and intermediate filaments to the cell membrane.
p.9
Muscle Contraction Mechanisms
What is the role of the Ca-calmodulin complex in smooth muscle contraction?
It activates myosin light chain kinase.
p.4
Bone Repair and Remodeling
What happens during bone repair after damage?
Osteoclasts create Howship's lacunae, which are later filled by osteoblasts with new bone.
p.6
Muscle Contraction Mechanisms
What determines the speed and strength of muscle contraction?
The interaction between heavy and light chains of myosin.
p.6
Muscle Contraction Mechanisms
What is a motor unit?
A motor neuron and the muscle fibers it supplies.
What are chondrosarcomas characterized by?
Elevated levels of SOX9, collagen types II and X, and aggrecan in biopsies.
p.2
Bone Formation Processes: Endochondral and Intramembranous Ossification
What is the first step in endochondral ossification?
Cartilage model formation from mesenchymal cells differentiating into chondroblasts.
p.6
Muscle Contraction Mechanisms
What is the T tubule system's role in muscle contraction?
It allows for synchronous contraction of all sarcomeres in the myofibril.
p.6
Muscle Contraction Mechanisms
What is a triad in muscle physiology?
A complex of a T tubule and two adjacent terminal cisternae.
p.6
Muscle Contraction Mechanisms
What is the role of acetylcholine receptors in muscle contraction?
They bind ACh, causing depolarization of the postsynaptic membrane.
what are the 4 zones of articular cartilage ?
<p>the superficial zone : flat chondrocytes surrounded by parallel collagen type 2 fibers</p><p>the middle transitional zone : round chodnrocytes with a high concentration of proteoglycans</p><p>the deep radial zone : perpendicular to collagen fibers</p><p>the calcified zone : anchord cartilage to the subchondral bone leaving behind a line called th etidemark</p><p></p>
