Muscles

Muscle = Latin Musculus = “Little Mouse”

Function of Muscles –

1. Movement of Skeleton

2. Control of Openings ex: mouth, anus

3. Stabilize Joints & Maintain Posture

4. Produce Heat when cold

5. Facial Expressions ex: happy, sad, fearful

6. Protection ex: eyes, mouth, internal organs

Nomenclature – Naming of Muscles

1. Shape ex: deltoid upside-down delta

2. Number of Heads or points of attachment ex: bicep = 2 heads

3. Length Short = Brevis, Long = Longus

ex: extensor carpus radalis longus

4. Location ex: biceps brachei – arm

biceps femoris – thigh

intercostal – between ribs

temporalis – over temporal bone

5. Attachments ex: sternocleidomastoid (sternum-clavicle-mastoid)

Function of Muscles –

1. Flexor & Extensor - fold and straighten

2. Adductor & Abductor – bring together and take away

3. Supinator & Pronator – palm up and palm down

Prime function of a muscle is to move or contract.

The Antagonist function is to relax

Attachment to Limbs –

Origins – proximal (nearest to midline) region of limb

Insertion – Distal (distance end away from midline) region of limb

Ex:

Origin Coracoid Process & Acromium Biceps brachii Insertion Proximal Radius

Histology of Muscles – 3 types

1. Smooth or Visceral – around hollow organs or tubes

2. Cardiac – heart

3. Skeletal or Striated – Attached to bones

These differ in structure, function and location.

Smooth or Visceral or Involuntary Muscle –

Made of single cells with a central nucleus and found in sheets held together by connective tissue.

Largest Smooth Muscles = Uterus and Digestive tract – peristalsis - slow rhythmic contractions

Greatest endurance = Pupil of eye, it is always working

Two muscles – radial and circular muscles

Smooth Muscle

Cardiac Muscle –

Tubular cells with central nuclei.

They are branched and have intercalated discs along the fibers that help facilitate the spread of the contraction and have striations.

Nuclei

Intercalated disc

Intercalated discs also increase the strength of the connection between cardiac muscle cells.

Cardiac Muscle

Skeletal Muscle –

Longest Muscle cells in the Sartorius 35cm or 14” long

Smallest Muscles in the Inner Ear 10u

Peripherally Multinucleated Cells make up fibers stronger than steel

Terms:

Sarcolemma “flesh” Cell membrane of a muscle cell

Sarcoplasm is the cytoplasm of muscle cells

Sarcomere is the functional unit of muscle contraction.

Actin and Myosin (sarcomere) Myofilaments Myofibrils

Muscle contract due to nerve impulse coming to sarcolema

Impulse Sarcolema Sarcolemic Reticulum Ca++ released

This causes the actin and myosin to slide together

“ Sliding Filament Theory”

Figure 08.07

Figure 08.08

Figure 08.09a

Figure 08.09b

Muscles of the Body

How many muscles do you have?

It was 638 until 1996 when a new muscle was found that connects from the orbit to the mandible so now it is 639.

Levator Palpabra

Splenius Capitis

Trapezius

Muscle of Head

Muscles of Head

Muscles of the Jaw –

7. Temporalis

O – Squamous portion of Temporal Bone

I – Coronoid process of Mandible

A – Close Jaw

8. Masseter – “chewer”

O – Zygomatic Arch

I – Angle and Ramus of Mandible

A – Close Jaw

Levator Palpabra

Splenius Capitis

Trapezius

Big Muscles of Trunk

1. Trapezius – tapezoid shaped found superior posterior

O – Occipital Bone & Ligamentum Nuchae (attaches to all the spines of Thoracic & Cervical vertebrae)

I – Spine of Scapula & Lateral 1/3 of Clavicle

A – Adduct scapula, depress scapula, raise scapula & extend head

Ligamentum Nuchae Scapula

ClavicleHead

2. Latissimus Dorsi –”Broad” lower back - Inferior Posterior

O – Thoraco Lumbar Faccia

I – Anterior Intertubercular Groove of Humerus

A – Medial Rotate Humerus, Adduct Humerus, Depress Humerus

3. Rotator Cuff - Connects Scapula to Humerus

Four Muscles – 1. Supraspinous Muscle

2. Infraspinous Muscle

3. Subscapularis Muscle

4. Teris Minor

O – Scapula

I – Proximal Humerus

A – Adduct & Abduct Humerus, rotate Humerus medial & lateral

Scapula

Humerus

Acromium

Ligamentum nuchae

Rotator Cuff

Aponeurosis

Arm & Forearm –

Muscles of the arm are for strength

Muscles of the forearm are for dexterity

Arm Muscles – Between shoulder and elbow

Biceps – 2 heads or points of origin (short and long head)

O – 1. Coracoid Process short head

2. Lip of Glenoid Fossa long head

I – Radial Tuberosity

A – Powerful Supinator (Hold a bowl of soup)

Flexor

Figure 08.21

Triceps – 3 heads – Posterior arm

1 on Scapula , 2 on proximal end of Humerus

O – Infra Glenoid Tubercle

Proximal Humerus stretching from medial to lateral

I – Olecranon Process of the Ulna (Elbow)

A – Extends forearm & stabilizes elbow joint

Forearm Muscles -

Brachio Radialis Muscles – Gives shape to forearm

Anterior Muscles flexor of wrist and fingers

Posterior Muscles Extensor of wrist and Fingers

Thenar Eminence – Large muscle at the base of the thumb

Figure 08.22

Anterior Superior Trunk Muscles -

1. Pectoralis Major – Chest Muscles

O – Sternum, Medial Clavicle, 2-6 Costal Cartilage

I – Outer lip of Intertubercular Groove of Humerus

A – Adduct & Medial Rotate Humerus

2. Deltoid – Gives shape to the shoulder

O – Lateral Clavicle & spine of Scapula

I – Deltoid Tuberosity of Humerus

A – Abduct Humerus and assist Bicep and Tricep

Abdominal Muscles –

All anterior muscles for the support and protection of abdominal & pelvic viscera. Contraction of these muscles flexes vertebral column.

1. Rectus Abdominus – Rectus = “straight” – major visible abdominal muscles known as a “six-pack”.

O – 5,6 & 7 Costal Cartilage and Xiphoid Process

I – Pubic Bone & Pubic Symphysis

Linea Alba – “white line” No blood vessels just connective tissue

Sternum

Rectus Abdominus

Pubic Bone

Linea Alba

Costal Cartilage Wrapped in aponeurosis of the External Obliques,

Internal Obliques & Transverse

Rectus Abdominus

E.O.

I.N.

Trans

Linea Alba

External Obliques – Very important muscles and aponeurosis

O – Lower RibsI - Linea AlbaAction -

1. Support & Potect Pelvic Viscera

2. Flex Vertebral Column

3. Aids in Breathing

4. Aids in Vomiting

5. Aids in Defecating

6. Aids in Childbirth

7. Used for laughing, coughing and sneezing

Folded bottom of aponeuroces forms Inguinal Canal. Testes descend through this canal after birth in males.

Inguinal Hernia – Intestines can get stuck in canal and get squeezed

Muscles of the Hip - 19 muscles in hip

Function - Flex & Extend, Adduct & Abduct, Circumduct

Two Groups of Muscles –

1. Gluteal Muscles – Posterior Pelvis / Buttock

Give shape to posterior pelvis

Humans have the largest Gluteal Muscles

Females have fat pads on top of the muscle

3 Muscles – Gluteal Maximus, Gluteal Medius and Gluteal Minimus

O – Ilium I – Posterior Ilium, Ileotibal band &

Greater Trochanter of Femur

Figure 08.26

2. Anterior Thigh Muscles –

1. Sartorius – called the “Taylor’s Muscle” – Let you sit cross legged.

O – Anterior Iliac Spine

I – Medial Proximal Tibia

A – Flex Hip Joint & Flex Knee Joint

2. Quadricep – 4 muscles

They are held together by Faccia Lata a tough fibrous wrapping

1. Rectus Femoris

2. Vastus Lateralis

3. Vastus Intermedus

4. Vastus Medialis

O – Ilium & Proximal Femur I – Quadriceps Tendon to Patella Tendon and Tibial Tuberosity.

A – Extends Leg

Figure 08.25

iliotibial band

Medial Thigh Muscle – Grailis “slender”

O – Pubic Bone I – Medial Proximal Tibia A – Adduct Thigh & Flex Knee

Posterior Thigh Muscles –

Hamstring - 1. Biceps Femoris

2. Semimembranosus

3. Semitendenosus

O – ischium I - Proximal Medial Tibia A - Extend Hip & Flex knee

Figure 08.27

Anterior Leg –

Front of Tibia has no muscles just periosteum containing nerves that’s why is hurts so much when you hit you shin.

Tibilas Anterior – Along sides of tibia connects to Dorum “top” of foot so you can pull you foot up.

Posterior Leg –

1. Gastrocnemius – superficial - gives shape to calf, large in humans

O – epicondyles of Femur I – Calcaneus (heel) via the Achilles Tendon

A – Extends foot called Plantar Flexon “plant on ground”

2. Soleus – deep muscle –

O – Proximal Fibia & Fibula I – Achilles Tendon A – Plantar Flexon

Figure 08.28

Figure 08.30

Figure 08.15

Figure 08.16