Anatomy EXAM 3 - SI TEST PREP

Osteocyte

mature bone cell

Osteoblast

Cells that make bone

Osteoclast

Cell that breaks down bone

Chondrocyte

Mature cartilage cell

Osteon

Unit of compact bone; made up of concentric circles called Haversian Canals

Calcitonin

Hormone that increases the deposition of calcium into the bones

Mesenchymal cells

Stem cells found in bone marrow

Osteoid

Organic, unmineralized part of bone matrix

Resting Zone

Cartilage on epiphyseal side of epiphyseal plate, inactive

Proliferation Zone

Cartilage on diaphysis side of epiphyseal plate, rapidly dividing, active, lengthening occurs because new cells are formed & old cells are pushed upward

Hypertrophic Zone

A part of the growth plate in the skeletal system where chondrocytes mature & prepare to calcify

Calcification Zone

Surrounding cartilage matrix calcifies, chondrocytes die

Ossification Zone

Calcified cartilage, covered with new bone by osteoclasts, replaced with spongy bone

Growth hormone

Most important hormone, stimulates epiphyseal plate, infancy & childhood

Thyroid hormone

Watches activity of growth hormone

Testosterone

A hormone that is produced used for maintaining & gaining bone mass in men

*Excess hormones cause abnormal growth

Parathyroid hormone

(PTH) A hormone that regulates calcium levels in the blood & bones

Complete fracture

Full break

Incomplete fracture

Not full break

Open (compound)

Skin is penetrated

Closed (simple)

Skin is NOT penetrated

Reduction

realignment of broken bone ends

Closed reduction

Manipulates position

Open reduction

Surgery/pins

Hematoma

Blood clot from torn blood vessels

What is in mature bone cells, maintaining the bone matrix, detecting mechanical stress on bone, may trigger deposition of new bone matrix?

Osteocyte

What does the loss of protein in the bones result in?

Brittle bones

What is the result of insufficient calcium in the bones?

Soft bones

The formation & development of bone connective tissue, also known as “osteogenesis”, 8th - 12th week of embryonic development, continuing through adolescence:

Ossification

Are osteons only found in compact bones?

Yes

When is the embryonic skeleton completed?

12 weeks gestation (1st trimester)

Where does hematopoiesis occur?

In the bone marrow

What are the 2 types of bone marrow?

1. Red

2. Yellow

Red bone marrow is active bone marrow, while yellow bone marrow is inactive; yellow in color because it is filled with adipose:

True

When is osteoid secreted?

During embryonic period & when new bone is formed

When does mesenchyme form & what does it condense?

Forms periosteum, condenses outer layer of spongy bone

What replaces spongy bone?

Compact bone

When do chondroblasts divide less often?

Near the end of adolescence

When does bone lengthening cease?

Females: 18 years

Males: 21 years

When do bones thicken?

Response to increased muscle activity or stress of weight on body

What percent of bone mass is recycled each week?

5 - 7%

What is apoptosis?

Plays a role in absorption, osteoclasts undergo it, & it controls cell death

What produces calcitonin?

Produced by parafollicular cells of thyroid gland, response to high calcium

What does wolf’s law state?

Bones grow & remodel in response to demands placed on them

3 types of muscle tissue

1. Skeletal

2. Cardiac

3. Smooth

Skeletal muscle (voluntary)

Attached to bones of skin, longest of all muscles & have striations (stripes), contract rapidly, tire easily, very powerful

Skeletal muscle fibers

Contract to help move bones & keep body shape

Voluntary muscles

Can be consciously controlled

Cardiac muscle (involuntary)

Only in heart, makes up heart walls, striated

Involuntary muscles

CANNOT be controlled

Smooth muscle (involuntary)

Not striated, found in walls of hollow organs, examples are stomach, urinary bladder, & airways

Muscle tissue characteristics

Excitability, contractility, elasticity, extensibility

Muscle functions

Produce movement, maintain posture & body position, to stabilize joints, & to generate heat as they contract

Skeletal muscle anatomy

Each muscle receives a nerve, artery, & vein

Actin filaments

Thin filaments

Myosin filaments

Thick filaments

Thick filaments

Composed of protein myosin

Thin filaments

Composed of fibrous protein actin

Tropin

Regulatory protein bound to actin

What muscle is the longest of all muscles due to its vast contractibility?

Skeletal muscle

What form of muscle cannot be controlled due to its connections with the nervous system?

Involuntary muscle

What are examples of muscle tissue characteristics?

Excitability, contractility, elasticity, extensibility

What is the plasma membrane of a muscle cell called?

Sarcolemma

The perimysium surrounds which of the following structures?

Fascicle

The attachment of a muscle to a movable bone is known as the _______.

Insertion

The connective tissue covering surrounding an entire muscle is called the ______.

Epimysium

What molecule stores oxygen in muscle cells?

Myoglobin

What are the 5 types of bone cells?

1. Osteoblast : Build bone by synthesizing matrix

2. Osteocytes : Mature bone cells maintaining matrix, sensing stress

3. Osteoclasts : Break down bone for remodeling/resorption

4. Osteoprogenitor Cells : Stem cells differentiating into osteoblasts

5. Bone Lining Cells : Cover bone surfaces, regulate mineral exchange

In order, what are the steps of endochondral ossification?

1. Cartilage model forms; Mesenchyme differentiates into a hyaline cartilage template

2. Cartilage grows; Chondrocytes hypertrophy, matrix calcifies

3. Primary ossification center forms; Blood vessels invade, osteoblasts replace cartilage with bone

4. Secondary ossification centers develop; Bone forms at epiphyses

5. Epiphyseal plate persists; Cartilage remains for longitudinal growth, later ossifies

What does troponin do when calcium binds to it?

Shifts tropomyosin to expose myosin-binding sites

How does calcium contribute to muscle contraction?

Binds to troponin, exposing actin’s myosin-binding sites for cross-bridge cycling

How does the parathyroid hormone increase calcium levels?

Stimulates osteoclasts, enhances kidney calcium reabsorption, & activates vitamin D

List the 3 primary mechanisms for ATP production in cells?

Creatine phosphate, Anaerobic pathway, Aerobic pathway

What is rigor mortis?

Postmortem muscle stiffening due to ATP depletion, locking myosin to actin

What is intramembranous ossification?

Bone formation directly from mesenchymal tissue without a cartilage precursor

Types of joints:

1. Synovial : Separated by fluid joint cavity (ex → Limb joints)

2. Cartilaginous : United by cartilage (hyaline), (ex → Pubic symphysis, intervertebral disc)

3. Fibrous : United by dense fibrous connective tissue (ex → sutures, gomphoses, syndesmosis)

What is the correct order of stages in fracture repair?

1. Hematoma formation

2. Fibrocartilaginous callus

3. Bony callus

4. Remodeling

What disorder is characterized by low bone density & increased fracture risk due to impaired bone remodeling?

Osteoporosis

Which condition involves excessive, irregular bone growth due to unbalanced osteoclast/osteoblast activity

Paget’s disease

What is osteomalacia in children caused by?

Vitamin D definciency

What does acetylcholinesterase do?

Breaks down acetylcholine in the synaptic cleft to prevent continuous stimulation

List the zones of the epiphyseal plate & their primary activities:

• Resting (inactive chondrocytes)

• Proliferation (chondrocyte division)

• Hypertrophic (matrix calcification)

• Ossification (bone replacement)

What is the sliding filament model of muscle contraction?

Actin slides past myosin, shortening the sarcomere via ATP-driven cross-bridges

List 4 characteristics of muscle tissue:

• Excitability

• Contractibility

• Extensibility

• Elasticity

What factors contribute to joint stability?

Ligaments, muscle tone, joint shape, synovial fluid/capsule

What 2 substances are primarily stored in muscle tissue?

Glycogen & myoglobin

What factors influence the velocity & duration of a muscle contraction?

Fiber type, load, motor unit recruitment

What are the 7 functions of the skeletal system?

1. Support

2. Protection

3. Movement

4. Mineral Storage

5. Blood Cell Production

6. Fat Storage

7. Hormone Regulation

What occurs during repolarization?

Membrane potential returns to negative as potassium exits the cell

What channels open & close during repolarization?

Sodium channels close, potassium channels open

What type of muscle fiber is best suited for endurance activities such as long-distance running?

Slow oxidative (Type 1) : High endurance, fatigue-resistant, rich in mitochondria & myoglobin

What triggers synaptic vesicles to release acetylcholine due to calcium entry?

Action potential at the axon terminal

What is the role of the axon terminal in the neuromuscular junction?

Releases acetylcholine into the synaptic cleft upon calcium influx

What defines a motor unit?

One motor neuron & all muscle fibers in innervates

Describe isotonic contractions:

Muscle length changes

Describe isometric contractions:

Muscle length stays constant

What are 3 phases of a muscle twitch?

• Latent period

• Contraction

• Relaxation

What sarcomere region contains both actin & myosin filaments?

A band

What factors primarily control bone remodeling?

Hormones, mechanical stress, cytokines/growth factors