Bone Formation: Ossification Processes

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Questions and Answers

What type of hair is fine and downy, found in the fetus during the third trimester?

Vellus

Lanugo (correct)

Terminal

Cortex

Which part of the hair is responsible for nourishing the hair and contains capillaries?

Hair papilla (correct)

Hair bulb

Hair follicle

Hair shaft

What primarily determines the shape and appearance of hair?

Shaft shape (correct)

Color of the hair

Total hair length

Density of hair follicles

What happens to hair when melanin production diminishes?

Hair turns gray Signup and view all the answers

Which layer of hair contains several layers of flattened cells and hard keratin?

Cortex Signup and view all the answers

What type of joint is the humeroradial joint?

Plane joint Signup and view all the answers

Which ligament helps bind the radius to the ulna?

Anular ligament Signup and view all the answers

Which joint structure allows for the largest range of motion in the hip?

Ball-and-socket joint Signup and view all the answers

What is the primary functional type of the knee joint?

Hinge joint Signup and view all the answers

What reinforces the stability of the hip joint?

Muscles and tendons from hip and thigh Signup and view all the answers

What is the first step in endochondral ossification?

Development of fetal hyaline cartilage model Signup and view all the answers

Which hormone is primarily responsible for stimulating chondrocyte activity during bone growth?

Growth Hormone Signup and view all the answers

What occurs during interstitial bone growth?

Lengthwise growth dependent on cartilage growth Signup and view all the answers

What is the primary reason bones change shape and strength throughout life?

Renewal and reshaping of bone mass Signup and view all the answers

What is the role of calcitriol in bone health?

Increases renal Ca2+ reabsorption Signup and view all the answers

In appositional bone growth, what occurs on the internal surface of the bone?

Bone is resorbed Signup and view all the answers

What happens to the epiphyseal plate after adolescence?

It closes and fuses epiphysis and diaphysis Signup and view all the answers

Which of the following factors primarily regulates bone remodeling?

Hormonal activity and mechanical stress Signup and view all the answers

What characterizes woven bone in the early stages of bone development?

Immature and unorganized structure Signup and view all the answers

What effect do glucocorticoids have on growth at the epiphyseal plate?

Interfere with growth Signup and view all the answers

What is the primary function of calcium release from the sarcoplasmic reticulum during muscle contraction?

To bind to troponin and expose myosin binding sites Signup and view all the answers

What happens to the I band and H zone during muscle contraction?

Both lengths shorten Signup and view all the answers

What role does acetylcholinesterase play in muscle relaxation?

It removes acetylcholine from the synaptic cleft Signup and view all the answers

Which of the following correctly describes the role of ATP during the powerstroke of muscle contraction?

ATP binds to myosin, allowing it to release from actin after the powerstroke Signup and view all the answers

What is the function of the DHP channels in muscle contraction?

To trigger the opening of RyR channels allowing calcium flow Signup and view all the answers

Which statement is true regarding the sliding filament mechanism of muscle contraction?

Thin filaments slide over stationary thick filaments towards the center of the A band Signup and view all the answers

What is the primary energy source for muscles during immediate contraction?

Phosphagen system Signup and view all the answers

How does myokinase contribute to ATP production in the muscle?

It transfers phosphate from one ADP to another to generate ATP Signup and view all the answers

What characterizes Type 2b muscle fibers?

Fast and powerful contractions Signup and view all the answers

Which type of contraction involves muscle shortening with tension?

Isotonic contraction Signup and view all the answers

What is the result of asynchronous recruitment of motor units?

Uniform distribution of contraction force Signup and view all the answers

What happens to Type 2b fibers after high-intensity aerobic training?

They become more oxidative and resemble Type 1 fibers Signup and view all the answers

Which of the following describes the process of wave summation?

Temporal summation of twitches leading to increased contraction strength Signup and view all the answers

Which muscle type does not contain sarcomeres?

Smooth muscle Signup and view all the answers

What is a key characteristic of Type 1 muscle fibers?

High amount of myoglobin for oxygen storage Signup and view all the answers

During muscular inactivity, what primarily occurs to skeletal muscle?

Atrophy and reduction of muscle mass and tone Signup and view all the answers

What do synergist muscles primarily do?

Stabilize the body during movement Signup and view all the answers

What is the primary function of the antagonist muscle during movement?

To stabilize a joint and control movement speed Signup and view all the answers

Which of the following adaptations is associated with aerobic endurance training?

Enhanced maximal aerobic power Signup and view all the answers

Which attachment is typically more stationary, the origin or the insertion?

Origin Signup and view all the answers

How do pennate muscles differ from non-pennate muscles?

Pennate muscles produce lower force due to a high angle of pennation Signup and view all the answers

What is the significance of myofibril synthesis in muscular hypertrophy?

Increases muscle fiber size and strength Signup and view all the answers

Study Notes

Ossification

Ossification is the process of bone formation, primarily from cartilage.
Intramembranous ossification forms directly from mesenchyme, without a cartilage model.
Endochondral ossification uses cartilage as a template for bone development.
Woven bone is immature and unorganized and is later replaced by lamellar bone.
The periosteum forms from mesenchyme that condenses around the developing bone.

Endochondral Ossification

Occurs in 6 steps:
- Fetal hyaline cartilage model forms
- Cartilage calcifies and the periosteal collar forms
- The primary ossification center develops in the diaphysis
- The secondary ossification center forms in the epiphysis
- Bone replaces cartilage, except for articular cartilage.
- Lengthwise growth continues until the epiphyseal plate ossifies.

Interstitial Bone Growth

Occurs in the epiphyseal plate, leading to bone lengthening.
Chondrocytes on the epiphyseal side of the plate divide and grow.
Chondrocytes calcify and die as they become deprived of nutrients.
Calcified cartilage is remodeled by bone tissue on the diaphysis side of the plate.

Appositional Bone Growth

Occurs at the outer surface of the bone leading to bone widening.
Bone is added to the external surface and resorbed on the internal surface.
Rate of bone addition is greater than bone resorption.

Bone Recycling

Bone is constantly being renewed and remodeled.
Compact bone is replaced more slowly than spongy bone.
Bone deposition and resorption are regulated by hormones and mechanical stress.

Hormones and Bone

Growth hormone stimulates liver to produce somatomedins, which stimulate chondrocyte activity.
Thyroid hormone regulates metabolic rate and promotes the activity of other hormones.
Sex hormones stimulate bone growth during puberty.
Glucocorticoids can interfere with growth at the epiphyseal plate.
Serotonin can act as a hormone to regulate bone remodeling.

Calcitriol, PTH, and Calcitonin

Calcitriol is the active form of vitamin D, produced by the skin on exposure to UV light.
Calcitriol increases intestinal reabsorption of calcium and phosphate.
Parathyroid hormone is secreted in response to low calcium levels, increasing osteoclast activity, calcium reabsorption in kidneys, and calcitriol production.
Calcitonin is secreted in response to high calcium levels, inhibiting osteoclasts and favoring calcium filtration in the kidneys.

Fractures and Repair

Fractures occur from bone breakage.
Bone repair involves stages of soft tissue formation, hard callus formation, and bony remodeling.

Hair Growth

Hair is made of dead epithelial cells, composed primarily of keratin.
Hair follicle surrounds the hair shaft.
Hair color is determined by melanin production.
Melanocytes are responsible for producing melanin.
There are three types of hair: lanugo, vellus, and terminal hair.

Hair Structure

Hair shaft extends above the skin surface.
Hair root lies below the skin surface.
Hair bulb is found at the base of the follicle and contains living epithelial cells.
Hair papilla is a projection of vascularized connective tissue that supplies nutrients to the hair bulb.

Elbow Joint

Includes three joints:
- Humeroulnar joint, humeroradial joint, and radioulnar joint.
Movements include flexion, extension, pronation, and supination.
Ligaments restrict side-to-side motion.

Hip Joint

Ball-and-socket joint.
Muscles and tendons reinforce stability.
Large range of motion is limited compared to the pectoral girdle.
Acetabular labrum deepens the joint socket.
Reinforcing ligaments include iliofemoral, ischiofemoral, and pubofemoral ligaments.

Knee Joint

Primarily a hinge joint.
Includes three joints:
- Two tibiofemoral joints, and one patellofemoral joint.
Menisci cushion the joint.
Limited rotation and lateral gliding occur.

Muscle Contraction

Muscle contraction is initiated by the arrival of an action potential, which releases calcium from the sarcoplasmic reticulum.
Calcium binds troponin, causing tropomyosin to move away from the myosin-binding sites on actin.
Myosin binds to actin, initiating the power stroke, which shortens the sarcomere during contraction.
Relaxation occurs when calcium is pumped back into the sarcoplasmic reticulum, breaking the cross-bridges between myosin and actin.

ATP and Muscle Metabolism

ATP is essential for muscle contraction and relaxation.
Muscle fibers use different metabolic pathways to supply ATP.
The phosphagen system provides immediate ATP for short-term contractions.
Glycolysis provides ATP for longer-term contractions but requires oxygen.
Different muscle fiber types have different contractile properties.

Muscle Types

Type 1 muscle fibers are slow-twitch fibers, small in diameter, with high amounts of myoglobin and numerous capillaries.
Type 2a muscle fibers are intermediate in size, with a moderate amount of myoglobin.
Type 2b muscle fibers are fast-twitch fibers, large in diameter with high amounts of glycogen and a small amount of myoglobin.

Twitches and Tetanus

Muscle contractions can be graded to produce different levels of force.
Wave summation occurs when muscle twitches are summed together resulting in a sustained contraction.
Incomplete tetanus results from rapid successive action potentials, producing a quivering contraction.
Tetanus is a smooth, sustained contraction from rapid successive action potentials.

Motor Unit Recruitment

Motor units are comprised of a single motor neuron and the muscle fibers it innervates.
Force of contraction is increased by recruiting more motor units.
Asynchronous recruitment helps prevent fatigue.

Muscle Contraction Types

Isotonic contractions maintain constant tension while muscle length changes.
- Concentric contractions shorten the muscle.
- Eccentric contractions lengthen the muscle.
Isometric contractions maintain constant muscle length while tension develops.

Muscular Adaptations: Hypertrophy

Hypertrophy is the increase in muscle fiber size due to training.
Includes increased synthesis of actin and myosin within myofibrils.
Improves power and force production.
Type 2 fibers have greater potential for hypertrophy.

Muscle Fiber Transitions

Muscle fiber types are genetically determined, but training can induce changes within subtypes.
High-intensity resistance training and aerobic endurance training can transform Type 2b to Type 2a muscle fibers.
Transition from Type 1 to Type 2 muscle fibers is less likely.

Body Composition Adaptations to Resistance and Sprint Training

Increased cytoplasmic, sarcoplasmic reticulum, and t-tubule density.
Enhanced calcium release from sarcoplasmic reticulum.
Decrease in blood and muscle pH during exercise.

Body Composition Adaptations to Aerobic Endurance Training

Increased aerobic capacity.
Increased maximal aerobic power.
Increase in size of Type 1 muscle fibers.
Increase in size and number of capillaries and mitochondria.

Effects of Inactivity

Skeletal muscle mass and tone decrease with sedentary lifestyles.
Muscle atrophy is reversible in the early stages.
Dying muscle fibers cannot be replaced.

Muscle Attachments

Muscles attach to bones via tendons or directly via epimesium.
Origin is the proximal (stationary) attachment site.
Insertion is the distal (mobile) attachment site.

Movement and Force Generation

Movements involve the coordinated action of multiple muscles.
Agonist muscle is the primary muscle responsible for movement.
Antagonist muscle opposes the agonist.
Synergist muscle stabilizes the body during movement.

Muscle Fiber Alignment

Pennate muscles have fibers that attach obliquely to the tendon, increasing cross-bridges per unit volume.
Non-pennate muscles have fibers that run parallel to the tendon, generating greater velocity.

Muscle Naming Conventions

Muscles are named based on their location, structure, size, shape, origin and insertion, and function.

Smooth Muscle

Smooth muscle lacks sarcomeres and has spindle-shaped cells with a single nucleus.
Contains dense bodies that act as attachment points for myosin and actin filaments.
Smooth muscle is found in the walls of hollow organs and is responsible for involuntary movements.
Smooth muscle contraction is slow and sustained.

Smooth Muscle Contraction and Relaxation

Smooth muscle contraction is initiated by calcium binding to calmodulin.
Calcium-calmodulin complex activates myosin light chain kinase, which phosphorylates myosin, allowing it to bind actin.
Relaxation occurs when myosin light chain phosphatase removes the phosphate from myosin, breaking the cross-bridges.

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Description

Explore the fascinating processes of ossification, including intramembranous and endochondral ossification. Learn how woven bone is replaced by lamellar bone and the significance of the periosteum. This quiz covers the steps involved in bone growth and development.