Basic Structure and Physiology of the Skeltal an

Basic Anatomy & Physiology of the Skeletal and Muscular Systems

Chapters 5 & 6

Learning Outcomes (Skeletal)

• State the major functions of the skeletal system
• Label and describe the structure of a long bone
• Label and describe the microscopic structure of a bone
• Compare and contrast the 3 types of bone cells
• Describe the process of bone remodeling
• Describe how PTH and calcitonin help regulate calcium
• Identify joints based on function
• Describe the major skeletal disorders discussed in class

Vocab Terms (Skeletal)

• Hematoma
• Fibrous callous
• Bony callous
• Parathyroid hormone
• Calcitonin
• Fibrous joint
• Cartilaginous joint
• Synovial joint
• Ligaments
• Fracture
• Transverse fracture
• spiral fracture
• comminuted fracture
• compound fracture

• Epiphysis
• Diaphysis
• Epiphyseal plate
• Red Marrow
• Yellow Marrow
• Articular Cartilage
• Osteon
• Osteocyte
• Lacuna
• Canaliculi
• Haversian Canal
• Osteoblast
• Osteoclast
• Bone remodeling

• green stick fracture
• osteoporosis
• osteogenesis imperfecta
• arthritis
• sprain

The Skeletal System Basics and Physiology

Major Functions of Skeletal System​​

• Support

• Protection

• Movement

• Storage

• Hematopoiesis

Basic Bone Structure

• Click on the on the photo to learn more about the structures of a basic long bone.

Microscopic Bone Structure

• Click on the on the photo to learn more about the microscopic bone structure.

Types of Bone Cells

Click on each bone cell to learn about their functions.

Bone Remodeling/Healing

Fibrocartilage callus forms

Bone remodeling occurs

Hematoma forms

Bony callus forms

Click on the play button to watch a video on the process of bone remodeling. Take notes while you watch.

Endocrine Control of Calcium Homeostasis

Parathyroid Hormone (PTH)

Calcitonin

• Gland: thyroid gland
• Stimulus for release: increased blood calcium (Ca2+)
• Target: osteoblasts

• Effect: increases osteoblast activity to use excess calcium in blood to create new bone tissue.
• Ultimately decreases blood calcium levels

• Gland: parathyroid glands (yellow dots on thyroid gland above)
• Stimulus for release: decreased blood calcium (Ca2+)
• Target: osteoclasts

• Effect: increases osteoclast activity to break down bone and release calcium into bloodstream.
• Ultimately increases blood calcium levels

Drag and drop the statements to fill in the feedback loop regarding calcium homeostasis

Blood calcium levels increase

Blood calcium levels decrease

Thyroid gland releases calcitonin

Parathyroid glands release PTH

Osteoclasts break down bone and release calcium into bloodstream

Osteoblasts use excess calcium in blood to create new bone tissue

Drag and drop the statements to fill in the feedback loop regarding calcium homeostasis

Osteoblasts use excess calcium in blood to create new bone tissue

Thyroid gland releases calcitonin

Blood calcium levels decrease

Parathyroid glands release PTH

Blood calcium levels increase

Osteoclasts break down bone and release calcium into bloodstream

Joints/Articulations

Click on each type of joint to learn more about their specific functions

A joint, also called an articulation, is a site where 2 or more bones meet. 2 functions:1. securely holds bones together 2. allow the skeleton to move when muscles contract **Note: many joints also have ligaments which provides additional support

Skeletal Disorders

Fractures

Osteoporosis

• reduced bone density
• Osteoclasts more active than osteoblasts
• increased risk of fracture
• more common in women >65 years old

Osteogenesis Imperfecta (OI)

• “Brittle bone disease”
• Genetic disorder that affects collagen -> reduces flexibility of bones -> cannot withstand outside force

Arthritis

• inflammation of joints
• Usually caused by “wear and tear” -> degenerating cartilage

• Symptoms: pain, swelling, redness, crepitus

Sprain

• Damage to ligament
• Usually caused by overuse or excessive stretching
• Symptoms: pain, swelling
• Ligaments have poor blood supply -> difficult to heal

Muscular System Basics & Physiology

Learning Outcomes (Muscular)

• State the major functions of the muscular system
• Compare and contrast the 3 types of muscular tissue
• Label and describe the basic structure of a muscle
• Label and describe the microscopic structure of a sarcomere
• Describe the steps of the sliding filament theory
• Identify and describe major movements
• Identify and describe the major muscular disorders discussed in class

Vocab Terms (Muscular)

• cross bridge
• power stroke
• rigor mortis
• flexion
• extension
• adduction
• abduction
• circumduction
• rotation
• dorsiflexion
• plantar flexion
• strain
• myasthenia gravis
• ALS
• Tetanus
• Botulism

• Skeletal muscle
• cardiac muscle
• smooth muscle
• muscle fiber
• myofibril
• sarcomere
• fascicle
• muscle
• tendon
• sliding filament theory
• actin
• myosin
• myosin binding sites

What are the functions of the muscular system?

• Contract to permit movement
• Maintain posture & body position
• Stabilize joints
• Generate Heat

Types of Muscle

Basic Muscle Structure

• Muscle fiber
• Myofibril
• sarcomere
• Fascicle
• Muscle
• Tendon

Microscopic Structure of a Sarcomere

Sliding Filament Theory

• Mechanism of muscle contraction
• Overarching goal
• Shorten the sarcomeres
• Myosin must interact with actin to “slide” the actin filaments towards the center of the sarcomere

Sliding Filament Theory: Step 1

The Neuromuscular Junction

• When an action potential reaches the axon terminal, ____ enters the axon terminal which causes the synaptic vesicles to release a neurotransmitter called ___________
• _________ binds to receptors on the surface of the muscle fiber and generates an action potential across the muscle.

Sliding Filament Theory: Step 1 (animated)

Sliding Filament Theory: Step 2

Intramuscular calcium release

• When the action potential spreads across the muscle fiber, it causes ____ to be released from the ________ ________ (a special structure in muscles that stores calcium)

Sliding Filament Theory: Step 3

Troponin Binding

• Calcium binds to _______ on the actin filament.
• This causes _________ to change shape and expose ________-binding sites

Sliding Filament Theory: Step 4

Cross-Bridge Formation & Powerstroke

• _____ on the myosin head breaks to provide the energy needed to form a _________ (myosin head attaches to actin filament)
• ADP + P release from myosin head to pull the actin filament towards the middle of the sarcomere (__________)

Sliding Filament Theory: Step 5

Cross-Bridge Release

• _____ must be added back to the myosin head to allow it to detach from the actin filament

Sliding Filament Theory

The process of forming a cross-bridge, power stroke, and then releasing the cross-bridge is repeated to allow the myosin heads to “walk” the actin filaments towards the center of the sarcomere.

Why does rigor mortis occur after death?

Body Movements

Flexion & Extension

Flexion decreases the angle of a joint - bringing 2 bones together

• In the video - when she lifts the weight

Extension increases the angle of a joint - increasing the distance between 2 bones

• In the video - when she lowers the weight

Adduction & Abduction

Abduction - moves a limb away from the body midline

• In the video - when she is raising the weights

Adduction - moves a limb toward the body midline

• In video - when she is lowering the weights

Circumduction

Circular movement

Rotation

Twisting motion at a joint

Dorsiflexion and Plantar Flexion

Up and down movements of the foot at the ankle

Dorsiflexion - point toes towards head

Plantar Flexion - points toes away from head

Muscular Disorders

Strain

Myasthenia Gravis

Amyotrophic Lateral Sclerosis AKA: ALS/Lou Gehrig’s Disease

Tetanus

Botulism

Haversian Canal

Central canal within an osteon through which blood vessels and nerves pass. The Haversian canal branches off into smaller canals known as canaliculi. This brings a blood supply to all of the bone cells throughout the compact bone tissue.

Storage

• Bones serve as a storage site calcium

Protection

Bones provide a hard, protective structure around vital organs. For Example:

• Skull protects brain
• Vertebral column protects spinal cord
• Thoracic cage protects heart & lungs

Diaphysis

"shaft" of long bone

The diaphysis (shaft) contains a cavity known as the medullary cavity which is surrounded by compact bone tissue

• In children, the medullary cavity contains red bone marrow
• In adults, the red bone marrow of the medullary cavity is replaced with yellow marrow (fat storage)

Movement

Muscles attach to bones. When they contract, it moves our skeleton @ joints

Lacuna

Plural: lacunae

Tiny cavities within bone tissue which contains osteocytes (mature bone cells) Each lacuna has a blood supply delivered to them by canaliculi (tiny canals that branch off from the Haversian canal to deliver blood to each lacuna)

Hematopoiesis

Blood cell formation

Red bone marrow is the site of all blood cell formation

Cartilagenous Joints

Slightly movable

Two bones are linked with hyaline cartilage. They generally have more movement than a fibrous joint, but less movement than synovial joints. Some examples include:

• Vertebral column
• thoracic cage - where ribs meet sternum
• pubic symphisis (where pubic bones meet)

Support

Our skeleton provides a scaffolding for muscles to attach to.

Fibrous Joints

Immovable

Fibrous joints are immovable joints - bones are tightly bound together by fibrous connective tissue. Common examples of fibrous joints:

• sutures of the skull
• tooth sockets

Spongy bone

Bone tissue found primarily in the ends of long bones (epiphysis). Contains red bone marrow which is the site of hematopoiesis

Osteoclast

Bone-destroying cells

Osteoclasts dissolve bone tissue that is old or damaged. They may also dissolve bone tissue when the body needs calcium to be released from storage and into the bloodstream.

Osteon

The functional unit of compact bone tissue. Composed of concentric rings made of collagen + calcium salts around a central canal (Haversian Cancal) which supplies the bone tissue with blood vessels and nerves

Articular Cartilage

Hyaline cartilage found at the ends of long bones. It provides cushion & protection to prevent bones from rubbing against each other at a joint.

• Hint: "articulation" refers to where two bones meet (a joint)

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Epiphyseal Plate

"Growth Plate"

A flat plate of cartilage (known as hyaline cartilage) that is seen in young, growing bone. It allows for lengthwise growth of a long bone. At the end of puberty, hormones stop long bone growth and the epiphyseal plate is completely replaced by bone.

Osteoblast

Bone-building cell

These cells replace hyaline cartilage with bone tissue as you grow and develop throughout childhood. They also are involved in bone repair. After a bone has been fractured, osteoblasts are involved in laying down new bone tissue at the site of the fracture.

Epiphysis

End of long bone

• Contains red bone marrow which is the site of hematopoiesis

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Osteocytes

Mature bone cells

Found primarily within lacuna of the osteon

Synovial Joints

Freely movable joints

Joints in which the ends of bones are separated by a joint cavity that contains synovial fluid (provides lubrication and cushioning). These joints are the most movable. Examples include

• joints of the limbs (shoulder, elbow, wrist, hip, knee, ankle)

Epiphysis

ends of long bone

Contains red bone marrow - site of hematopoiesis