Muscular System
The muscular system generally functions to control the movement of the skeleton, to stabilize joints, maintain posture, produce heat, manipulate facial expressions for emotional conveyance and protection from damage (closing eyes, motion of arms to protect from falling or from an incoming object). The nomenclature is an extension of skeletal anatomy which includes the shape, number of heads and length of muscle. The origin is at the proximal portion of the limb and insertion is at the distal end of the limb. A muscles nomenclature typically gives an indication of the function of the muscle.
Muscles are peripheral, multi-nucleated cells that have a cell membrane called sarcolemma (sarco = flesh lemma = membrane). The cytoplasm is called sarcoplasm and within the sarcoplasm are myofibrils. Myofibrils are composed of myofilaments which are composed of actin and myosin. They are both aligned and give the appearance of striations that can be seen when viewed under a microscope. There are three types of muscle histology; smooth, cardiac and skeletal, each with unique structure, function and location.
Myosin, also called A bands and Actin, also called Z bands constructs a matrix, which are called I bands. Coming down through the I bands are Z bands and the area in between the Z bands are called the sarcomere which is the structural and functional unit of skeletal muscle. During contraction, the Z bands approach each other and decrease the sarcomere.
Nerve impulses are transferred to the sarcolemma and the response is transferred internally to the sarcoplasmic reticulum (smooth endoplasmic reticulum) which discharges a calcium ion that triggers the Z bands to contract resulting in a sliding filament of muscle contraction.
The effective action of muscles are to flex, extend, adduct, abduct, supinate (palm up), pronate (palm down) and circumrotate. The following is a list of relevant muscles of the head, neck and body, that includes a description of their shape, origin (proximal beginning), insertion (distal attachment) and functional description
Muscles of the Orbit
Lateral Rectus - lateral side of eyeball in orbit
Superior Rectus - superior side of eyeball in orbit
Medial Rectus - medial side of eyeball in orbit
Inferior Rectus - inferior side of eyeball in orbit
Superior Oblique - Innervated by the trochlear nerve, the smallest cranial nerve yet has the longest course
Levator Palpebrae - origin is superior aspect of the orbit and insertion is to the upper eyelid; raises the eyelid (droopy eyelid indicates a 3rd Cranial Nerve Lesion)
Muscles of the Head and Neck
Frontalis - covering of the frontal bone, no bony attachment, used to raise eyebrows and wrinkle the forehead
Orbicularis Oculi - Round muscle around the orbit, closes the eyelid
Nasalis - Cheek bone
Orbicularis Oris - Round muscle around the mouth, closes the mouth, origin is cheek muscles insertion is contralateral mouth.
Muscles of the cheek - Buccinator (means trumpet, purses lips to expel air) origin is maxilla and mandible and insertion is contralateral of mouth, closes the mouth with contraction. useful for chewing, smiling, motor portion of the Vth cranial nerve, can push food back into mouth when moves laterally.
Muscles of the jaw; temporalis originates on squamous portion of temporal bone and insertion on coronoid process of mandible; contracts it closes the jaw; can exert significant amount of pressure, very powerful muscles. masseter means chewer, originates on the zygomatic arch and insert on ramus of jaw to close it
Platysma - flat muscle anterior neck
Sternocleidomastoid - Sternum, clavicle, mastoid process in Temporal Bone (Mastoid - a conical process of the temporal bone behind the ear, to which neck muscles are attached and which has air spaces linked to the middle ear.)
Muscles of the Arms
Arm and leg muscles are designed for strength, forearm muscles are designed for dexterity.
Rotator Cuff: Infraspinatus
Supraspinsatus - the most superior of the four rotator cuff muscles, it is a small triangular shaped muscle at the posterior and superior aspect of the scapula
Teres Minor
Teres Major
Trapezius - trapezoid shape; origin is occiput and insertion is vertebral column, cervical and thoracic vertebrae.
(ligamental nuchae is the ligament that attaches all of the spines of cervical and thoracic vertebrae)
Deltoid - thick, triangular shaped muscle that forms the rounded contour of the shoulder, origin is scapula and clavicle insertion on the deltoid tuberosity of the humerus
Biceps - two heads, long head and short head, it is a powerful supinator and flexes the forearm, both attach to the scapula,
Triceps Brachii- three headed muscle, long head, lateral head, and medial head
Brachioradialis - comes from the humerus to radius, lateral forearm, gives shape of the lateral forearm, anterior portion have flexors of wrist and fingers, posterior have extensors
Flexor Carpi Radialis/Flexor Carpi Ulnaris - Muscles opposite of the brachioradialis, Carpi Radialis is larger and more medial, ulnaris is smaller and more lateral
Thenar Muscles: Opponens Pollicis is the largest of the thenar muscles and lies underneat the other two. Abductor Pollicis Brevis (APB), is found anterior to the Opponens Pollicis and proximal to the Flexor Pollicis Brevis, The Flexor Pollicis Brevis (FPB) is the most distal to the thenar muscles.
Thenar Eminence - big muscle at the base of the thumb
Hypothenar Eminence - big muscle opposite and below the base of the thumb
Dorsal Interosseous Muscles - there are four (1-4) dorsal interosseous muscles that insert into the extensor expansion of the corresponding extensor digitorum tendon
Muscles of the Trunk
Lattisimus Dorsi - means broad, is inferior and posterior, lower back, lumbar and thoracic vertebrae, originates from thoracolumbar fascia, a layer of strong connective tissue, fascia comes up from the ilium, thoracolumbar fascia attaches to the crest of the ilium and lower thoracic spines, attaches to the lasttisiumus dorsi and blends with the muscle and inserts on the anterior intertuburcular groove of the humerus; it medial rotates the humerus
Pectoralis Major - Anterior Muscles of the Chest lateral to the manubrium, sternum and xiphoid, adducts the humerus, medial rotates the humerus
Xiphoid - the Xiphoid is the smalliest region of the sternum, and is made up of cartilage at birth but develops into bone as an adult, it serves as an attachment point for organs and large muscles that make the floor of the diaphragm; phrenic nerve attachment
Intercostals at ribs -
Abdominals - Rectus Abdominus - protect and support the abdominal and pelvic viscera; have spleen and pancreas that need to support and protect, all anterior, they contract to flex the spine/vertebral column. in between the xiphoid and pubic bones with the umbilicus at midline have two bellies of muscle in layers. in the middle they connect with the aperneurosis. there is a thin midline that doesn't have any muscle but a layer of connective tissue called the linea alba, no blood vessels, just a white line.
External oblique - supports and protects the abdominal and pelvic viscera, flexes the vertebral column, aids in vomiting, defecation and childbirth
Muscles of the pelvic floor
Levator ani - originates on the pubic bone and ischium inserts on the coccyx posteriorly and median raphe; in women there are three openings, urethra, vagina and anus; levator ani is medial and lateral support, median raphe is posterior to the anus, strengthens the anus
superficial transversus
Anal Sphincter - the anal sphincter is a thin, circular muscle that wraps around the anal canal
Muscles of the Hips and Leg
There are 19 muscles here in general to flex, extend, adduct and abduct.
Fascia Lata is a think strong encasement of connective tissue fascia around thigh muscles; fascia lata, there is an iliotibial band
Gluteal muscles; pelvis, gluteus maximus, ilieum to femor medius and minimus
Iliopsoas - at the crease of the proximal lower extremites, action is to, there is a major artery here.
Thigh muscles - crosses from anterior iliac spine to medial proximal tibial
Sartorius - tailors muscle, flexes the hip, flexes the knee joint
Quadriceps; big thigh muscles; anterior thigh encased in fascia lata
Rectus Femoris - comes from the ilium, insert quadriceps tendon surrounding the patella and patellar ligament inserts on tibial tuberosity
Vastus Lateralis - comes from proximal femur
Vastus Intermedius -comes from proximal femur
Vastus Medialis - comes from proximal femur
Hamstrings; give shape to posterior thigh and consist of these three muscles:
Biceps Femoris
Semimembranosis
Semitendinosus
Anterior Leg
Tibialis Anterior - lateral head of tibia to first metatarsal and first tarsal bone
Posterior leg
Gastrocnemius - bi-headed muscle, gives the shape to posterior calf, very large, originates at the medial and lateral epicondyles of the femur
Soleus - the soleus muscle is a flat, broad muscle of the calf that lies inferior to the gastrocnemius muscle
Peroneus Longus - starts at the top of the fibula and traverses the outside of the leg inferior to the knee; it moves ankles, flexes the foot and maintains balance
Intrinsic Muscles of the Foot
Abductor Hallucis - midline muscle of the arch of the foot
Flexor Digitorum Brevis - superior aspect at the foot, distal to the plantar aponeurosis tendon
Muscles are peripheral, multi-nucleated cells that have a cell membrane called sarcolemma (sarco = flesh lemma = membrane). The cytoplasm is called sarcoplasm and within the sarcoplasm are myofibrils. Myofibrils are composed of myofilaments which are composed of actin and myosin. They are both aligned and give the appearance of striations that can be seen when viewed under a microscope. There are three types of muscle histology; smooth, cardiac and skeletal, each with unique structure, function and location.
Myosin, also called A bands and Actin, also called Z bands constructs a matrix, which are called I bands. Coming down through the I bands are Z bands and the area in between the Z bands are called the sarcomere which is the structural and functional unit of skeletal muscle. During contraction, the Z bands approach each other and decrease the sarcomere.
Nerve impulses are transferred to the sarcolemma and the response is transferred internally to the sarcoplasmic reticulum (smooth endoplasmic reticulum) which discharges a calcium ion that triggers the Z bands to contract resulting in a sliding filament of muscle contraction.
The effective action of muscles are to flex, extend, adduct, abduct, supinate (palm up), pronate (palm down) and circumrotate. The following is a list of relevant muscles of the head, neck and body, that includes a description of their shape, origin (proximal beginning), insertion (distal attachment) and functional description
Muscles of the Orbit
Lateral Rectus - lateral side of eyeball in orbit
Superior Rectus - superior side of eyeball in orbit
Medial Rectus - medial side of eyeball in orbit
Inferior Rectus - inferior side of eyeball in orbit
Superior Oblique - Innervated by the trochlear nerve, the smallest cranial nerve yet has the longest course
Levator Palpebrae - origin is superior aspect of the orbit and insertion is to the upper eyelid; raises the eyelid (droopy eyelid indicates a 3rd Cranial Nerve Lesion)
Muscles of the Head and Neck
Frontalis - covering of the frontal bone, no bony attachment, used to raise eyebrows and wrinkle the forehead
Orbicularis Oculi - Round muscle around the orbit, closes the eyelid
Nasalis - Cheek bone
Orbicularis Oris - Round muscle around the mouth, closes the mouth, origin is cheek muscles insertion is contralateral mouth.
Muscles of the cheek - Buccinator (means trumpet, purses lips to expel air) origin is maxilla and mandible and insertion is contralateral of mouth, closes the mouth with contraction. useful for chewing, smiling, motor portion of the Vth cranial nerve, can push food back into mouth when moves laterally.
Muscles of the jaw; temporalis originates on squamous portion of temporal bone and insertion on coronoid process of mandible; contracts it closes the jaw; can exert significant amount of pressure, very powerful muscles. masseter means chewer, originates on the zygomatic arch and insert on ramus of jaw to close it
Platysma - flat muscle anterior neck
Sternocleidomastoid - Sternum, clavicle, mastoid process in Temporal Bone (Mastoid - a conical process of the temporal bone behind the ear, to which neck muscles are attached and which has air spaces linked to the middle ear.)
Muscles of the Arms
Arm and leg muscles are designed for strength, forearm muscles are designed for dexterity.
Rotator Cuff: Infraspinatus
Supraspinsatus - the most superior of the four rotator cuff muscles, it is a small triangular shaped muscle at the posterior and superior aspect of the scapula
Teres Minor
Teres Major
Trapezius - trapezoid shape; origin is occiput and insertion is vertebral column, cervical and thoracic vertebrae.
(ligamental nuchae is the ligament that attaches all of the spines of cervical and thoracic vertebrae)
Deltoid - thick, triangular shaped muscle that forms the rounded contour of the shoulder, origin is scapula and clavicle insertion on the deltoid tuberosity of the humerus
Biceps - two heads, long head and short head, it is a powerful supinator and flexes the forearm, both attach to the scapula,
Triceps Brachii- three headed muscle, long head, lateral head, and medial head
Brachioradialis - comes from the humerus to radius, lateral forearm, gives shape of the lateral forearm, anterior portion have flexors of wrist and fingers, posterior have extensors
Flexor Carpi Radialis/Flexor Carpi Ulnaris - Muscles opposite of the brachioradialis, Carpi Radialis is larger and more medial, ulnaris is smaller and more lateral
Thenar Muscles: Opponens Pollicis is the largest of the thenar muscles and lies underneat the other two. Abductor Pollicis Brevis (APB), is found anterior to the Opponens Pollicis and proximal to the Flexor Pollicis Brevis, The Flexor Pollicis Brevis (FPB) is the most distal to the thenar muscles.
Thenar Eminence - big muscle at the base of the thumb
Hypothenar Eminence - big muscle opposite and below the base of the thumb
Dorsal Interosseous Muscles - there are four (1-4) dorsal interosseous muscles that insert into the extensor expansion of the corresponding extensor digitorum tendon
Muscles of the Trunk
Lattisimus Dorsi - means broad, is inferior and posterior, lower back, lumbar and thoracic vertebrae, originates from thoracolumbar fascia, a layer of strong connective tissue, fascia comes up from the ilium, thoracolumbar fascia attaches to the crest of the ilium and lower thoracic spines, attaches to the lasttisiumus dorsi and blends with the muscle and inserts on the anterior intertuburcular groove of the humerus; it medial rotates the humerus
Pectoralis Major - Anterior Muscles of the Chest lateral to the manubrium, sternum and xiphoid, adducts the humerus, medial rotates the humerus
Xiphoid - the Xiphoid is the smalliest region of the sternum, and is made up of cartilage at birth but develops into bone as an adult, it serves as an attachment point for organs and large muscles that make the floor of the diaphragm; phrenic nerve attachment
Intercostals at ribs -
Abdominals - Rectus Abdominus - protect and support the abdominal and pelvic viscera; have spleen and pancreas that need to support and protect, all anterior, they contract to flex the spine/vertebral column. in between the xiphoid and pubic bones with the umbilicus at midline have two bellies of muscle in layers. in the middle they connect with the aperneurosis. there is a thin midline that doesn't have any muscle but a layer of connective tissue called the linea alba, no blood vessels, just a white line.
External oblique - supports and protects the abdominal and pelvic viscera, flexes the vertebral column, aids in vomiting, defecation and childbirth
Muscles of the pelvic floor
Levator ani - originates on the pubic bone and ischium inserts on the coccyx posteriorly and median raphe; in women there are three openings, urethra, vagina and anus; levator ani is medial and lateral support, median raphe is posterior to the anus, strengthens the anus
superficial transversus
Anal Sphincter - the anal sphincter is a thin, circular muscle that wraps around the anal canal
Muscles of the Hips and Leg
There are 19 muscles here in general to flex, extend, adduct and abduct.
Fascia Lata is a think strong encasement of connective tissue fascia around thigh muscles; fascia lata, there is an iliotibial band
Gluteal muscles; pelvis, gluteus maximus, ilieum to femor medius and minimus
Iliopsoas - at the crease of the proximal lower extremites, action is to, there is a major artery here.
Thigh muscles - crosses from anterior iliac spine to medial proximal tibial
Sartorius - tailors muscle, flexes the hip, flexes the knee joint
Quadriceps; big thigh muscles; anterior thigh encased in fascia lata
Rectus Femoris - comes from the ilium, insert quadriceps tendon surrounding the patella and patellar ligament inserts on tibial tuberosity
Vastus Lateralis - comes from proximal femur
Vastus Intermedius -comes from proximal femur
Vastus Medialis - comes from proximal femur
Hamstrings; give shape to posterior thigh and consist of these three muscles:
Biceps Femoris
Semimembranosis
Semitendinosus
Anterior Leg
Tibialis Anterior - lateral head of tibia to first metatarsal and first tarsal bone
Posterior leg
Gastrocnemius - bi-headed muscle, gives the shape to posterior calf, very large, originates at the medial and lateral epicondyles of the femur
Soleus - the soleus muscle is a flat, broad muscle of the calf that lies inferior to the gastrocnemius muscle
Peroneus Longus - starts at the top of the fibula and traverses the outside of the leg inferior to the knee; it moves ankles, flexes the foot and maintains balance
Intrinsic Muscles of the Foot
Abductor Hallucis - midline muscle of the arch of the foot
Flexor Digitorum Brevis - superior aspect at the foot, distal to the plantar aponeurosis tendon