Sistema Locomotor: Sistema Muscular

Unit 3: Locomotor System (II): Muscular System

• The muscular system consists of skeletal muscles and tendons.

Functions of the Muscular System

• Produces movement
• Maintains posture via muscle tone
• Controls body temperature through muscle contraction
• Participates in ventilation by facilitating inspiration and expiration
• Supports the visceral mass

Anatomy of a Skeletal Muscle

• Formed by striated muscle fibers that have sarcolemma and sarcoplasm
• Muscle fibers are grouped in bundles
• Satellite cells participate in regeneration

Connective Tissue

• Connective tissue surrounds the muscle and muscle fibers and contains blood vessels and nerves
• 3 layers of connective tissue include epimysium, perimysium, and endomysium
• Epimysium covers the entire muscle
• Perimysium surrounds bundles of fibers
• Endomysium surrounds each individual fiber

Muscle Fibers

• Cells that contain a membrane called the sarcolemma
• Sarcoplasm contains myofibrils composed of actin and myosin myofilaments
• Myofibrils are surrounded by sarcoplasmic reticulum, that stores calcium ions, (Ca+2)
• Each fiber has mitochondria and T tubules connected to each other
• The function of T tubules is to facilitate the transmission of the nerve impulse
• The repetition of myofilaments forms the functional unit of the muscle: the sarcomere

Tendons

• Bands of dense connective tissue
• Connect muscles to bones, skin, or other muscles
• Provide great resistance to stretching
• A flat tendon is called an aponeurosis

Types of Muscles by Shape

• Long muscles are fusiform in appearance and have tendons at the ends
• Examples of long muscles include biceps, triceps, and sartorius
• Wide muscles are as long as they are wide and have a flattened appearance
• Examples of wide muscles include the transverse abdomen and diaphragm
• Short muscles have small dimensions
• Examples of short muscles include those in the hands and feet
• Annular muscles have a ring shape and are located around orifices
• Examples include the orbicular muscle of the lips and the sphincter muscle of the anus

Types of Muscles by Fiber Arrangement and Insertion Type

• Acintados have fibers oriented in the direction of the muscle's axis and are often long muscles
• Penniform muscles have fibers inserting on the sides of the tendon at an angle, similar to a feather
• Semipenniform muscles have fibers inserting on only one side of the tendon at an angle

Head Muscles

• Muscles responsible for facial expression
• Muscles of mastication
• Muscles of the tongue and pharynx
• Muscles that move the eyeball
• Muscles associated with the nasal cavity

Facial Expression Muscles

• Orbicularis oris closes the mouth and action of the beak (kissing/pouting)
• Buccinator compresses as the cheeks
• Risorius pulls the face back at the corners and creates a smile
• Mentoniano elevates the chin and lower lip
• Depressors of the angle of the mouth are responsible for descending the lips
• Platsyma facilitates the creation of pouting expressions
• The zygomatic major and minor aids the action of smiling
• Occipito frontalis assists elevating the eyebrows
• Temporoparietal allows for movement of the ears
• Orbicular of the eye closes the eyelids
• Levator of the eyelid elevates the upper eyelid

Mastication Muscles

• Temporalis elevates and retracts the mandible
• Masseter elevates the mandible and controls pressure

Tongue and Pharynx Muscles

• The tongue is moved by extrinsic muscles, which participates in chewing, swallowing, and speech
• Pharynx is responsible for swallowing

Globe of the Eye Muscles

• Rectus superior moves the globe up and inward
• Rectus inferior moves the globe down and inward
• Rectus lateral and medial moves the globe outward
• Oblique superior moves the globe down and outward
• Oblique inferior moves the globe up and outward

Nasal Fossae Muscles

• Procerus is located between the eyebrows
• Nasalis dilates the nasal orifices
• Mirtiform or septum depressor reduces the nasal orifices and lowers the nasal wings
• Elevator of the wing of the nose elevates the nasal wings

Neck Muscles

• Sternocleidomastoid allows for turning and tilting the head
• Laryngeal muscles consist of extrinsic and intrinsic muscles:
  • They stabilize the larynx during swallowing
  • Control the tension of the vocal cords
• Scalenes, that are posterior, participate in flexion of the neck
• Longus colli are in front of the cervical vertebrae, which assists in movements of flexion and rotation of the head

Trunk Muscles

• Trunk muscles include spinal column muscles, oblique and rectus muscles, and pelvic floor muscles

Spinal Column Muscles

• Associated with the spine from the first vertebra to the sacrum
• Functions include extension and flexion of the column, and rotation of the column

Oblique and Rectus Muscles

• External and Internal intercostals elevate and descends the ribs
• Obliques of the abdomen: internal and external
• Rectus abdomens occupies the central zone, with a connective band that forms the linea alba
• Diaphragm intervenes in pulmonary ventilation

Pelvic Floor Muscles

• Support the organs of the pelvic cavity
• Flex the sacrum and coccyx
• Control the passage of substances through the urethra and anus

Shoulder Girdle Muscles

• Muscles include those that stabilize the shoulder girdle and muscles involved in arm movements

Muscles That Stabilize The Shoulder Girdle

• Trapezius aids in movement of the shoulders
• Levator scapulae and rhomboids elevates and rotates the scapula
• Serratus anterior contributes to fixing the scapula and participates in the shoulder movement
• Subclavius displaces the clavicle, shoulder, and scapula forward with the pectoral minor

Muscles Involved With Shoulder Movement

• Pectoral major assists with flexion of the shoulder, rotation, and adduction of the humerus
• Deltoids abduct, flex, rotate, and extend the humerus
• Latissimus dorsi produces the shoulder extension together with the teres major
• Teres major, together with the teres minor, infraspinatus, and subscapularis, rotate the shoulder

Upper Limb Muscles

• Includes muscle involved with movement of the forearm and muscles involved with movement of the hand and fingers

Muscles Involved in Forearm Movement

• Triceps brachii: posterior, causes its extension
• Biceps brachii: anterior, causes arm flexion and supination of the forearm

Muscles Involved in Hand and Finger Movement

• Extrinsic: located in the forearm
  • Extensor muscles are on the back of the forearm, and flexors are at the front
  • Only tendons enter into the hand and the fingers
• Internals: originate in the carpus and the metacarpus and allow for the extension and the flexion of the fingers in the joints of the phalanxes in which, only the tendons arrive

Pelvic Girdle Muscles

• Psoas major facilitates the contraction flexes the hip, which originates in the lumbar vertebrae. Which unites the iliac muscle, forming the iliopsoas
• Adductors: pectineus and gracilis approximate the leg to the central axis of the body (adduction)
• Gluteus maximus, medius, and minimus form the buttock and are responsible for the extension and rotation of the hip
• Tensor fascia lata: flat muscle that attaches to the iliotibial tract
• Sartorius is mainly a synergistic muscle, which assists in hip flexion, abduction, and femoral rotation, knee flexion, and tibial rotation

Lower Limbs

• Lower limbs are muscle involved in leg and foot movements

Muscles Involved in Leg Movement

• Extensors: 3 vastus muscles and rectus femoris muscle
  • The extensors make up the quadriceps femoris
  • These muscles attach to the tibia and give rise to the extension of the leg
• Flexors: hamstring muscles
  • The flexors attach to the tibia and fibula
  • Contraction produces flexion of the knee

Muscles Involved in Foot and Toe Movement

• Plantar flexibility:
  • Gastrocnemius (calves)
  • Soleus
  • Attach to the calcaneal (Achilles) tendon
• Tibialis anterior opposes the plantars
• Foot also contains interior muscles