L5 The Muscular System Overview

The Muscular System

• There are over 600 named skeletal muscles in the human body
• Muscle tissue is present almost everywhere in the body

Muscles

• Muscles are a type of tissue that can contract to produce movement
• There are three main types of muscle tissue: skeletal, smooth, and cardiac

Types of Muscle Tissue

• Skeletal muscle: Voluntary, striated, attached to bones and cross joints
• Smooth muscle: Found in viscera and blood vessels, involuntary, non-striated
• Cardiac muscle: Found in the heart (myocardium), involuntary, striated, autorhythmic

Skeletal Muscle

• Voluntary muscle
• Striated muscle tissue
• Attached to bones and crosses joints

Attachment of Skeletal Muscle

• Origin: The fixed end of the muscle, typically proximal to the insertion
• Insertion: The movable end of the muscle, attached to another structure
• Tendon: Connective tissue that attaches muscle to bone
• Aponeurosis: Broad, flat tendon
• Raphe: A seam of fibrous tissue that connects muscle to muscle

Muscle Functional Groups

• Prime movers: Primary muscles responsible for a specific movement
• Synergists: Muscles that assist the prime movers
• Antagonists: Muscles that oppose the action of the prime movers
• Fixators: Muscles that stabilize the origin of the prime mover

Skeletal Muscle Structure

• Epimysium: Dense irregular connective tissue that surrounds the entire muscle belly
• Perimysium: Connective tissue septa that divides the belly into fascicles, which contain bundles of muscle fibers
• Endomysium: Fine connective tissue extensions of the perimysium that surround individual muscle fibers

Muscles of the Upper Limb

• Shoulder girdle: Muscles connect the upper limb to the thoracic cage, vertebral column, and scapula
• Upper arm: Muscles in the anterior and posterior compartments
• Forearm: Muscles in the anterior and posterior compartments
• Hand: Muscles in the thenar and hypothenar eminences, tendons of flexor muscles, and other small muscles

Shoulder Girdle Muscles

• Muscles connecting the upper limb to the thoracic cage:
  • Pectoralis major: Flexes and adducts the upper arm
  • Pectoralis minor: Depresses and protracts the scapula
• Muscles connecting the upper limb to the vertebral column:
  • Trapezius: Elevates, depresses, retracts, and rotates the scapula
  • Latissimus dorsi: Extends, adducts, and medially rotates the upper arm
• Muscles connecting the scapula to the humerus:
  • Deltoid: Abducts, flexes, and extends the shoulder joint

Muscles of the Upper Arm

• Anterior compartment:
  • Biceps brachii: Flexes the elbow and supinates the forearm
  • Brachialis: Flexes the elbow
• Posterior compartment:
  • Triceps brachii: Extends the elbow joint

Muscles of the Forearm

• Anterior compartment:
  • Flexors of the wrist and fingers
• Posterior compartment:
  • Extensors of the hand and fingers

Muscles of the Hand

• Thenar eminence: Muscles control the thumb
• Hypothenar eminence: Muscles control the little finger
• Tendons: Tendons of the long flexors pass through the hand
• Other small muscles: Carry out fine motor control

Muscles of the Lower Limb

• Gluteal region: Muscles that control movements of the hip joint
• Thigh: Muscles divided into anterior, posterior, and medial compartments
• Leg: Muscles divided into anterior, posterior, and lateral compartments
• Foot: Muscles that control movements of the foot

Gluteal Region Muscles

• Gluteus maximus: Extends the hip joint
• Gluteus medius: Abducts the thigh at the hip joint
• Gluteus minimus: Abducts the thigh at the hip joint

Muscles of the Thigh

• Anterior compartment:
  • Quadriceps femoris: A powerful extensor of the knee joint
• Posterior compartment:
  • Hamstring group (biceps femoris, semitendinosus, semimembranosus): Flexors of the knee joint
• Medial compartment:
  • Adductors of the thigh

Muscles of the Leg

• Anterior compartment:
  • Extensors of the ankle and toes
• Posterior compartment:
  • Flexors of the ankle and toes
  • Tibialis posterior: Inverts the foot
• Lateral compartment:
  • Peroneus longus and peroneus brevis: Evert (turn outward) the foot

Muscles of the Foot

• Muscles in the foot control fine movements

Muscles of the Thorax

• Intercostal muscles: Help with breathing
• Diaphragm: Primary muscle of respiration
• Serratus posterior superior: Elevate the ribs
• Serratus posterior inferior: Depress the ribs

Muscles of the Abdomen

• External oblique: Flexes and rotates the vertebral column
• Internal oblique: Flexes and rotates the vertebral column
• Transversus abdominis: Compresses the abdomen
• Rectus abdominis: Flexes the vertebral column
• Quadratus lumborum: Extends and laterally flexes the vertebral column
• Psoas major: Flexes the hip joint
• Iliacus: Flexes the hip joint

Muscles of the Pelvis

• Levator ani: Forms the pelvic diaphragm and supports pelvic organs

Muscles of the Head

• Scalp: Occipitofrontalis muscle
• Facial expression: Muscles that control facial expressions
• Mastication: Muscles that control chewing

Muscles of the Scalp

• Occipitofrontalis: Raises eyebrows and wrinkles the forehead

Muscles of Facial Expression

• Eyelids:
  • Levator palpebrae superioris: Lifts the upper eyelid
  • Orbicularis oculi: Closes the eyelid
• Lips:
  • Orbicularis oris: Closes the mouth
• Cheeks:
  • Buccinator: Compresses the cheeks and helps with chewing

Smooth Muscle

• Spindle-shaped cells with a single, centrally located nucleus
• Non-striated and involuntary, controlled by the autonomic nervous system
• Found in blood vessels, glands, gastrointestinal tract, and lower respiratory tract

Cardiac Muscle

• Cylindrical cells with branches that connect end-to-end
• One centrally located nucleus, with intercalated discs
• Involuntary and autorhythmic, controlled by the autonomic nervous system
• Found only in the myocardium (heart muscle tissue)

Nerve Supply of Muscles

• Smooth and cardiac muscles: Autonomic nerves (sympathetic and parasympathetic)
• Skeletal muscles: Somatic nerves (e.g., spinal nerves)

Explore the fascinating details of the muscular system, including the three main types of muscle tissue: skeletal, smooth, and cardiac. This quiz covers their characteristics, functions, and structural relationships, enhancing your understanding of how muscles operate in the human body.