The Skeletal System: Functions and Structure

Functions of the Skeletal System

• The skeletal system provides support for the body.
• It protects internal organs from injury.
• It facilitates movement by providing attachment points for muscles.
• It stores minerals like calcium and phosphorus.
• It produces red blood cells in the bone marrow.

Bone Count

• Babies have approximately 300 bones at birth.
• Adults have 206 bones.

Bone Structure

• Compact bone provides strength and support.
• Spongy bone contains red bone marrow for blood cell production.
• Bone marrow is involved in the production of blood cells.

Vertebral Column

• The vertebral column consists of 33 irregularly shaped bones called vertebrae.
• The vertebrae are divided into five categories based on their location in the backbone.
• The first cervical vertebra is called the atlas.
• The second cervical vertebra is called the axis.
• The atlas allows the head to nod "yes".
• The axis allows the head to shake "no".
• Each vertebra has a hollow center for the spinal cord to pass through, providing protection.
• Cartilage is present between vertebrae.

Movement Types - Adduction

• Adduction involves movement toward the midline of the body.
• Abduction involves movement away from the midline.
• Jumping jacks involve upwards movement.

Movement Types - Abduction

• Abduction is a movement away from the midline.
• Raising the arms out to the sides of the body is an example of shoulder abduction.
• Adduction is a movement towards the midline.
• Squeezing the legs together is an example of hip adduction.

Movement Types - Circumduction

• Circumduction is a circular movement of a body part that combines flexion, abduction, extension, and adduction.
• Rotation is movement around a fixed axis or spinning a body part on its center.
• Moving the arm at the shoulder to trace a circle with the hand is an example of circumduction.
• Turning the head from side to side is an example of rotation.

Movement Types - Flexion and Extension

• Flexion is bending a limb or joint.
• Extension is straightening a limb or joint, increasing the angle between body parts.
• Straightening the knees when standing up is an example of extension.

Movement Types - Supination and Pronation

• Supination of the foot occurs when weight rolls onto the outer edges of the feet.
• Pronation occurs when the foot rolls inward during walking or running.

Functions of the Skeletal System

• The skeletal system supports the body.
• It facilitates movement.
• It protects internal organs.
• It produces blood cells.
• It stores and releases minerals and fat.

Vertebrae Count

• Cervical: 7
• Thoracic: 12
• Lumbar: 5
• Sacrum: 5
• Coccyx: 4

Other Body Parts

• Ribcages
• Pelvis
• Cranium

Examples of Movements in Exercises

• Star Jump: Abduction
• Kicking a ball: Extension of the leg
• Turning the key in the door lock: Rotation
• Pitching a softball: Circumduction

Bone Classification - Long Bone

• Long bones are found in the limbs.
• They serve as levers for movement.
• Long bones have a greater length than width.
• They are mostly compact bone.
• Examples include the femur, humerus, ulna, radius, tibia, and fibula.

Bone Classification - Short Bone

• Short bones are very strong but have less movement.
• They are nearly equal in length and width.
• Short bones are mostly spongy bone with an outer layer of compact bone.
• Examples include carpals and tarsal bones.

Bone Classification - Flat Bone

• Flat bones are usually thin.
• They consist of two layers of compact bone covering a thin layer of spongy bone.
• Flat bones provide protection and a large area for muscle attachment.
• Examples include the cranium, sternum, and ribs.

Bone Classification - Irregular Bone

• Irregular bones mainly provide protection and support.
• Examples include the mandible and vertebrae.
• They don’t fit into other bone classification categories due to their complex shapes.

Bone Classification - Sesamoid Bone

• Sesamoid bones relieve tension and stress on tendons and muscles, acting as an additional attachment point.
• An example is the patella.
• Sesamoid bones are commonly found embedded within a muscle or tendon near joint surfaces.
• They are classified based on shape or function.

Connective Tissues

• Muscles are attached to bones; when a muscle contracts, they pull on bones to create movement.
• Joints are where two bones meet.
• Ligaments connect bone to bone to create a joint.
• Tendons are connective tissue that connects muscle to bone and provides stability to the joint.
• Joints have three different classifications: fixed, cartilaginous, and synovial.

Joint Classifications - Fixed

• Movement: None
• Examples: Skull, pelvis

Joint Classifications - Cartilaginous

• Movement: Slight movement
• Examples: Ribs, sternum

Joint Classifications - Synovial

• Movement: Free movement
• Examples: Hip, knee, ankle

Synovial Joints

• Synovial joints are the most common type of joint in the body, allowing for the greatest amount of movement.
• Articular cartilage encases the ends of the bones within the joint cavity.
• Synovial fluid acts as a lubricant, allowing bones to move smoothly across each other without rubbing.

Synovial Joints - Examples

• Ball and Socket joint allows flexion, extension, adduction etc, and is found in the shoulder and hip.
• Hinge joints allow flexion and extension and are found in the knee and elbow.
• Condyloid joints allow flexion, extension, abduction, circumduction and are found in the wrist.

Muscular System

• The muscular system is responsible for the movement of the human body.
• Approximately 700 named muscles attach to the bones of the skeletal system.
• Muscles make up roughly half of a person’s body weight.
• The muscular system maintains bodily processes such as breathing and digestion and supports the circulatory system.

Skeletal Muscles

• Skeletal muscles are attached to bones and consciously controlled for everyday activities.
• They are known as voluntary muscles.

Smooth Muscles

• Smooth muscles maintain bodily processes that cannot be consciously controlled.
• They are known as involuntary muscles.

Cardiac Muscle

• Cardiac muscle is involuntary.
• Cardiac muscle makes up the walls of the heart.

Muscle Types - Skeletal Muscle

• Type: Voluntary
• Examples: Biceps, Triceps, Quadriceps, Hamstrings
• Location: Attached to bones via tendons
• Contraction Type: Voluntary (controlled by the brain and nervous system)
• Function: Enables movement, maintains posture and stability, produces heat

Muscle Types - Smooth Muscle

• Type: Non-striated, Involuntary
• Examples: Stomach, Intestines, Blood Vessels, Bladder
• Location: Found in the walls of organs (digestive tract, blood vessels, uterus)
• Contraction Type: Involuntary (controlled automatically by the nervous system)
• Function: Helps in digestion, regulates blood flow, supports organ function

Muscle Types - Cardiac Muscle

• Type: Striated, Involuntary
• Examples: Heart Muscle (Myocardium)
• Location: Only found in the heart
• Contraction Type: Involuntary (beats on its own with signals from the heart’s pacemaker)
• Function: Pumps blood throughout the body, maintains circulation and oxygen delivery, works 24/7 without tiring

Cardiovascular System

• The circulatory system consists of the heart, blood, and blood vessels.
• It circulates blood, transporting oxygen, nutrients, and water to cells.
• It removes wastes.
• It helps maintain body temperature.
• It fights disease by circulating white blood cells and antibodies.
• The superior vena cava (SVC) conveys venous blood from the upper half of the body and returns it to the right atrium.
• Arteries carry oxygen away from the heart.

Heart Facts

• The average heart is close to the size of an adult fist.
• At rest, the heart pumps blood around the body at between 60 to 70 bpm.
• Maximum heart rate is roughly 220 minus age.
• Blood vessels supply blood to the working parts of the body, including arteries, capillaries, and veins.

Blood Vessels - Arteries

• Arteries carry blood that is rich in oxygen away from the heart.

Blood Vessels - Capillaries

• Capillaries are small blood vessels where the exchange of nutrients and wastes occurs between the body cells and the blood.

Blood Vessels - Veins

• Veins carry blood that is low in oxygen back to the heart.

Acute Responses to Exercise

• The body responds physiologically to meet the increased energy demands of the activity.
• These immediate short-term responses last only for the duration of the activity and the recovery period.
• Acute responses vary depending on the intensity and duration of exercise.

Cardiac Output

• CO = HR x SV
• Stroke Volume is the amount of blood pumped out of the left ventricle per beat (ml/beat).
• Cardiac Output is the amount of blood the LV pumps per minute (L/beat).
• Cardiac Output will change if stroke volume and heart rate increases or decreases.

Respiratory System

• The respiratory system brings air from the atmosphere into the lungs.
• It supplies oxygen to the body.
• It removes carbon dioxide.

Respiratory System - Inspiration

• Inspiration is the movement of air from the external environment into the lungs (breathing in).

Respiratory System - Expiration

• Expiration is the movement of air out of the lungs to the external environment (breathing out).

Respiratory Volumes - Respiratory Rate

• Respiratory Rate is the number of breaths taken within a minute.

Respiratory Volumes - Tidal Volume

• Tidal Volume is the amount of air breathed in and out in one breath.

Respiratory Volumes - Ventilation

• Ventilation combines inspiration and expiration during a one minute period.
• Minute ventilation is calculated by: tidal volume X respiratory rate

Respiratory Volumes - Residual Volume

• Residual Volume is the amount of air left in the lungs following a maximal exhalation.

Respiratory Volumes - Vital Capacity

• Vital Capacity is the maximum amount of air that can be expired (breathed out) after a maximal inspiration.

Respiratory Volumes - Total Lung Capacity

• Total Lung Capacity is the volume of air that can be held in the lungs after a maximum inspiration, approximately 6L for males and 4.2L for females.

Gas Exchange (Pulmonary Diffusion)

• Pulmonary diffusion is the process to describe the exchange of gases in the lungs through a thin membrane, from high to low concentration.
• The alveoli/capillary interface is the location where the exchange of gases, including oxygen (O2) and carbon dioxide (CO2), occurs between the bloodstream and lungs.
• CO2 wants to move from a high concentration in the capillaries to a low concentration in the alveoli.
• CO2 and O2 are exchanged across a thin membrane, blood is oxygenated and returns back to the heart, and CO2 is exhaled out of the body.