Functional Anatomy

Agonist muscles are the primary muscles responsible for a specific movement, while antagonist muscles oppose that movement. For example:

1. Bicep Curl:

   • Agonist: Biceps Brachii
   • Antagonist: Triceps Brachii

2. Leg Extension:

   • Agonist: Quadriceps
   • Antagonist: Hamstrings

3. Chest Press:

   • Agonist: Pectoralis Major
   • Antagonist: Latissimus Dorsi

The major muscle groups include:

1. Deltoids
2. Pectorals
3. Biceps
4. Abdominals
5. Trapezius
6. Triceps
7. Latissimus Dorsi
8. Quadriceps
9. Gluteals
10. Hamstrings
11. Gastrocnemius (calf)

The reference position of the body is called the anatomical position.

Muscles, bones, and joints work together to allow twisting, turning, bending, straightening, and rotating movements.

Most movements have an opposite to them.

Flexion is the movement that involves bending and decreasing the angle between two bones.

Extension is the movement that involves straightening and increasing the angle between two bones, which is the opposite of flexion.

Abduction is the movement of a bone away from the centerline of the body in either the horizontal or vertical plane.

Adduction is the movement of a bone towards the centerline of the body in either the horizontal or vertical plane, which is the opposite of abduction.

Circumduction is the movement of a bone so that the end describes a circle, creating a conical shape as it moves around.

Rotation refers to the movement of a bone around its longitudinal axis.

Supination is the movement of the bones of the forearm so that the radius and ulna are parallel, resulting in the palms facing upwards.

Pronation is the movement of the bones of the forearm so that the radius and ulna cross over each other, resulting in the palms facing downwards.

Inversion is the movement of the sole of the foot inwards at the ankle joint.

The key characteristics of skeletal muscle tissue include:

1. Contractibility - The ability to shorten and generate force.
2. Extendibility - The ability to be stretched without damage.
3. Elasticity - The ability to return to its original shape after being stretched.

The different types of muscle contractions include:

1. Eccentric - Muscle lengthens while producing force.
2. Concentric - Muscle shortens while producing force.
3. Isometric - Muscle length remains the same while producing force.

The origin and insertion points of skeletal muscles determine their action by:

• Origin - The fixed attachment point that does not move during contraction.
• Insertion - The movable attachment point that moves towards the origin during contraction.

The relative positions of these points influence the direction and type of movement produced by the muscle.

The cranium protects the brain and forms the structure of the skull.

The clavicle is known as the collarbone, extending horizontally from the top of the rib cage.

The rib cage consists of ribs that protect the heart and lungs.

The femur is the longest bone in the human body, extending from the hip to the knee.

The patella, or kneecap, protects the knee joint and aids in leg movement.

The fibula is the outer bone of the lower leg, extending from the knee to the ankle.

Metatarsals are the bones in the foot located between the ankle and the toes.

The mandible is the jawbone that allows for chewing and speaking.

The humerus is the upper arm bone, extending from the shoulder to the elbow.

The ulna is the inner bone of the forearm, extending from the elbow to the wrist, and helps in forearm rotation.

Carpals are the bones of the wrist that allow for wrist movement.

Metacarpals are the bones of the hand located between the wrist and the fingers, providing structure and support.

Phalanges are the bones of the fingers and toes, allowing for dexterity and movement.

The tibia is also known as the shinbone, extending from the knee to the ankle.

Tarsals are the bones of the ankle that provide stability and support for the foot.

1. Involuntary Muscles: Also known as smooth muscles, found in internal organs like the intestine, and are not under conscious control.

2. Cardiac Muscles: Found only in the heart, these muscles are also not under conscious control and are responsible for pumping blood throughout the body.

3. Voluntary Muscles: Also called skeletal muscles or striped muscles, these are under our control and enable movement.

The three main types of muscle tissue are:

1. Skeletal Muscle: Voluntary control, responsible for movement of the skeleton.
2. Smooth Muscle: Involuntary control, found in digestive, respiratory systems, and blood vessels.
3. Cardiac Muscle: Involuntary control, makes up the heart muscle and contracts throughout a human's life without exhaustion.

• Spindle-shaped, nonstriated, uninucleated fibers
• Occurs in walls of internal organs
• Involuntary

• Striated, branched, uninucleated fibers
• Occurs in walls of the heart
• Involuntary

• Striated, tubular, multinucleated fibers
• Usually attached to the skeleton
• Voluntary

The primary function of cardiac muscle tissue is to pump blood throughout the body, and it is involuntary in nature.

• Controlled by nerve impulses
• Capable of contraction and stretching with force while retaining elasticity
• Subject to wasting (atrophy) or growth (hypertrophy)

Contractibility refers to the ability of skeletal muscle to contract forcefully when stimulated. It follows the 'All or none principle', meaning the muscle will either contract with full force or not at all, depending on whether the signal from the brain exceeds a certain threshold.

Elasticity is the ability of skeletal muscles to return to their original length after contraction or extension.

Extensibility refers to the muscle's ability to stretch without being damaged. Skeletal muscle can stretch beyond its normal resting length, up to one and a half times its normal length.

The two ends of a muscle are called the origin and the insertion. The origin is at the non-moving end, while the insertion is at the moving end.

Tendons are critical components of skeletal muscles, connecting muscles to bones at both ends, facilitating movement across joints.

Muscles must cross a joint to create movement because the contraction of the muscle pulls on the tendon at the insertion point, allowing the joint to move.

The Biceps and Triceps are examples of muscles that cross the elbow joint, with their tendons serving as origin and insertion points for movement.

The origin is where the bone originates or starts, and it is the stationary bone that the muscle attaches to. This represents the more stable joint or attachment.

The insertion is where the bone attaches to another bone, specifically the point where the tendon joins the moving bone.

The two basic types of skeletal muscle action are isometric contraction and isotonic contraction. Isotonic contractions further divide into concentric and eccentric contractions.

An isometric contraction occurs when the muscle contracts but does not shorten, resulting in no movement.

A concentric contraction occurs when the muscle shortens while generating force, resulting in movement.

An eccentric contraction occurs when the muscle lengthens while generating force, also resulting in movement.

Isotonic contractions cause the muscle to change length and generate movement of a body part.

The two types of isotonic contractions are concentric and eccentric.

During concentric contractions, the muscle shortens as it contracts.

Bending the elbow from a straight position to a flexed position causes the bicep brachii muscle to contract and shorten.

Concentric contractions occur frequently in daily and sporting activities.

Eccentric contractions occur when the muscle lengthens as it contracts, in contrast to concentric contractions where the muscle shortens. Eccentric contractions are less common than concentric contractions.

An example of an eccentric contraction is when moving the elbow from a flexed position to a straightened position, where the bicep is lengthening and contracting simultaneously.

Isometric contractions occur when there is no change in the length of the contracting muscle, meaning the muscle generates force without moving the joint. The force produced depends on the muscle's length at the point of contraction, with each muscle having an optimum length for maximum force production.

One example of an isometric contraction is when you grip something, such as a tennis racket. In this case, there is no movement in the joints of the hand, but the muscles are contracting to maintain a steady hold on the racket.

The amount of force a muscle can produce during isometric contractions is influenced by the length of the muscle at the point of contraction. Each muscle has an optimum length at which it can generate maximum isometric force.

The bicep undergoes a concentric contraction during elbow flexion, where the muscle shortens as it generates force to lift the forearm.

The tricep undergoes an eccentric contraction during elbow extension, where the muscle lengthens while controlling the movement of the forearm.

There are three main types of muscle contractions:

1. Isometric Contraction - Muscle length does not change.
2. Isotonic Contraction - Muscle changes length while maintaining tension.
   • Concentric - Muscle shortens.
   • Eccentric - Muscle lengthens.

The contraction in which the muscle does not change its length is called Isometric Contraction.

In muscle anatomy, the term origin refers to the point where a muscle attaches to a stationary bone, typically located closer to the center of the body. It is the fixed attachment point that does not move during muscle contraction.

Elasticity in muscle tissue refers to the ability of muscle fibers to return to their original length after being stretched or contracted. This property allows muscles to withstand stretching and maintain their shape and function during movement.

During a full bicep curl, the following types of contractions occur:

1. Concentric Contraction - As you lift the weight towards your shoulder, the biceps muscle shortens, causing the arm to flex.
2. Eccentric Contraction - As you lower the weight back down, the biceps muscle lengthens while still under tension, controlling the descent of the weight.
3. Isometric Contraction - At the top of the curl, if you hold the weight in place, the biceps may engage in isometric contraction to maintain the position without changing length.

The primary functions of skeletal bones include:

1. Support - Provides structural support for the body.
2. Protection - Protects vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).
3. Storage - Stores minerals such as calcium and phosphorous.
4. Red Blood Cell Production - Occurs in the red marrow of long bones.
5. Movement - Provides attachment points for skeletal muscles, facilitating movement.

Joints are sites where bone meets bone and are classified according to the amount and type of movement they permit.

Ligaments connect bone to bone across joints, providing stability and preventing dislocation. They are slightly elastic, allowing for some small movement of the bones at the joint.

Immoveable or fibrous joints are joints where bones are fixed or fused together by strong bands of fibrous tissue. They allow no movement and primarily serve the function of protection. Examples include sutures in the skull, the pelvis, the sacrum, and the sternum.

Slightly moveable or cartilaginous joints are joints where the bone ends are separated by a disc or plate of cartilage. Only small amounts of movement are possible. Examples include the vertebrae and the joints where the ribs join the sternum.

• Bone ends are covered with cartilage
• The cavity of the joint contains a lubricating fluid called synovial fluid
• Ligaments usually hold the bones together
• They are the most common type of joint in the body
• Examples include: knee, elbow, ankle, hip, shoulder, finger, wrist

The types of freely moving/synovial joints include:

1. Hinge - allows movement in one plane, like a door.
2. Pivot - allows rotation around a single axis.
3. Gliding - allows sliding movements between flat surfaces.
4. Ball and Socket - allows movement in multiple directions, like the shoulder and hip.
5. Saddle - allows movement in two planes, resembling a saddle shape.
6. Condylar - allows movement but with limited rotation, like the wrist.

• Convex surface fits into concave surface
• Movement is only possible in one plane
• Movement is similar to a door swinging on its hinges
• Examples include the elbow, knee, and knuckle.

The primary characteristic of ball and socket joints is that the ball of one bone fits into the socket of another, allowing for the greatest range of movement among joint types.

Examples of ball and socket joints in the human body include the shoulder joint and the hip joint.

• Bone surfaces are almost flat
• Allow only a very slight gliding motion
• When many gliding joints work together, they can produce significant movement

Examples of gliding joints include:

• Carpal bones
• Tarsal bones

A saddle joint has a saddle-like structure where one bone fits into the other. This allows for a range of motion, particularly enabling the thumb to be placed across the hand. An example of a saddle joint is found between the carpal and metacarpal of the thumb.

A pivot joint consists of a ring-like structure of one bone that fits around the pivot-like structure of another bone, allowing for rotational movement.

Examples of pivot joints include:

1. Radio-ulna joint
2. Joint between the 1st and 2nd vertebrae (allows head rotation)

An ovoid or condylar joint is characterized by an oval-shaped head of one bone fitting into a shallow cavity on another bone, allowing for movement in two anatomical planes.

Ovoid or condylar joints allow movement in two anatomical planes, enabling a range of motion that includes flexion, extension, abduction, and adduction.

Examples of ovoid or condylar joints include:

• Carpals of the wrist and the radius
• Articulation between the metacarpals of the palm and the phalanges of the fingers

Flexion/Extension, Abduction/Adduction, Circumduction

Flexion/Extension

A little movement in all directions

Immovable joints are also referred to as fibrous joints.

Slightly moveable joints are referred to as cartilaginous joints.

Freely moveable joints are also referred to as synovial joints.

There are six different types of freely moveable joints.

A hinge joint is classified as a uniaxial joint.

The ball-and-socket joint allows the most movement.

One type of freely moveable joint is the ball-and-socket joint. It allows for rotational movement and movement in multiple directions. An example is the shoulder joint, where the humerus fits into the scapula, allowing for a wide range of motion.

Eversion is the movement of the sole of the foot outwards at the ankle joint, which is the opposite of inversion.

Dorsiflexion is the movement of the top of the foot towards the tibia, which is the opposite action to plantar flexion.

Plantar flexion is the movement of the top of the foot away from the tibia, achieved by pointing the toes.

Elevation is the movement that involves raising the shoulder girdle upwards in relation to the head.

Depression is the movement that involves lowering the shoulder girdle downwards in relation to the head, which is the opposite of elevation.

The origin is the tendon attachment at the non-moving end of the muscle.

The insertion is the tendon attachment at the moving end of the muscle.

Muscles must cross a joint for movement to occur, and movement occurs at that joint.