Muscle & Integumentary System

Unit 9 - Muscle & Integumentary System

• Muscles
• Nearly ½ body’s weight.
• ~600 human skeletal muscles.
• Specialized for one purpose → transforming ATP into mechanical energy of motion.
• Types:

1. Cardiac
2. Skeletal
3. Smooth muscle

• Overview

1. Muscle

• Muscle Cells and Types of Muscle

• Muscle Tissue

• Muscles of the Head

• Muscles of the Thoracic and Abdominal Regions

• Muscles of the Shoulder and Upper Limb

• Muscles of the Hip and Lower Limb

2. Integument

• Anatomy of the Skin

• Anatomy of Hair, Nails, and Glands

• Muscular Tissue - Muscle Characteristics
• Muscle characteristics

1. Excitability/responsiveness

• To chemical signals, stretch, and electrical signals.

1. Conductivity

• Waves of excitation through muscle fibre.

1. Contractility

• Shortens when stimulated.

1. Extensibility

• Capable of being stretched between contractions.

1. Elasticity

• Returns to its original rest length after stretching.
• Skeletal muscle
• Striated muscle attached to bone:
  • Striations from arrangement of internal contractile proteins.
• Voluntary.
• Muscle cell = muscle fibre (myofibre):
  • Can be 30cm long!

• Myofilaments
• Fibrous proteins that carry out the contraction:

1. Thick:

• Hundreds of gold-club shaped myosin molecules.
• Heads directed outward in a helical array.

1. Thin:

• Two intertwined strands of fibrous actin:
  • String of globular actin subunits that can bind to head of myosin molecule.

1. Elastic:

• Made of a huge springy protein called titin:
  • Run through the core of each thick filament and anchor it.

• Muscle Fiber (Muscle cell)
• Sarcolemma
  • Plasma membrane of a muscle fibre.
• Sarcoplasm
  • Cytoplasm of muscle fiber.
    • Myofibrils
    • Glycogen
    • Myoglobin (Binds to 1 oxygen)
• Multiple nuclei
• Many Mitochondria
• Sarcoplasmic reticulum (SR)
  • Smooth ER forms a network around each myofibril.
• T (transverse) tubules - tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the side.

• Neuromuscular Junction
• Skeletal muscle only contracts when stimulated by a nerve.
• Denervation atrophy is shrinkage of a paralyzed muscle when a nerve is disconnected.

• Smooth Muscle
• Slower than other muscle types:
  • Can remain contracted for a long time without fatigue.
• Forms layers within walls of hollow organs.
• Can provide fine control in some locations:
  • Piloerector muscles.
  • Iris smooth muscle controls pupil size.
• Myocyte:
  • Fusiform shape with one nucleus.
  • Have thick and thin filaments, but not aligned with each other (no striations).
• Types of Smooth Muscle
• Multiunit smooth muscle
  • Occurs in some of the largest arteries and air passages, piloerector muscles, iris of eye.
  • Autonomic innervation forms motor units:
    • Each motor unit contracts independently.
• Single-unit smooth muscle:
  • More common.
  • Called visceral muscle, two layers, inner circular and outer longitudinal.
  • Cells are electrically coupled via gap junctions.
• Comparison of Skeletal, Cardiac, and Smooth Muscle:

• Functions of Muscle

1. Movement

• Physically moving, moving body contents in breathing, circulation, and digestion.
• Communication (speech, writing, expressions)

1. Stability

• Maintain posture by preventing unwanted movements, stabilize joints, and presence of antigravity muscles.

1. Control of body openings and passages

• Sphincters are internal muscular rings that control movement of food, blood, etc.

1. Heat production

• Skeletal muscle produces as much as 85% of our body heat.

1. Glycemic control

• Absorb and store glucose, which helps regulate blood sugar.
• Connective Tissues and Fascicles

1. Endomysium

• Thin sleeve of loose connective tissue around each fibre.

1. Perimysium

• Thicker layer of connective tissue that wraps fascicles (bundles of muscle fibres).

1. Epimysium

• Fibrous sheath surrounding entire muscle.

1. Fascia

• Sheet of connective tissue that separates neighbouring muscles or muscle groups from each other.

• Fascicles and Muscle Shapes

1. Fusiform (thick in the middle, tapered at each end)
2. Parallel (uniform with parallel fascicles)
3. Triangular (convergent, fan-shaped)
4. Pennate (feather-shaped), which has three types:
5. Unipennate (muscle on one side of tendon)
6. Bipennate (muscle on both sides of tendon)
7. Multipennate (multiple “feathers”)
8. Circular (sphincters, which form certain body openings)

• Compartments
• Group of functionally related muscles enclosed by fascia:
  • Contains nerves and blood vessels that supply the muscle group.
• Intermuscular septa:
  • Very thick fascia that separate one compartment from another.
• Muscle Attachments
• Muscles attach to bones through extension of connective tissue components:

1. Indirect:

• Tendons connect muscle to bone.
  • Collagen fibers of the endo-, peri-, and epimysium continue into the tendon and from there into the periosteum and matrix of bone.

1. Direct (fleshy):

• Little separate between muscle and bone.
• Muscle seems to emerge directly from bone (but there's a small gap between muscle and bone).

Indirect:

Direct:

• Muscle Origins and Insertions
• Origin
  • Bony attachment at stationary end of muscle.
• Belly
  • Thicker, middle region between origin and insertion.
• Insertion
  • Bony attachment to mobile end of muscle.
• Some anatomists prefer proximal vs distal or superior vs inferior.
• Functional Groups of Muscles
• An action is the effect produced by a muscle, whether it is to produce or prevent movement.
• Muscles seldom act independently, movement is the combined action of multiple muscles.
• Action of muscle depends on what other muscles are doing.
  • Gastrocnemius usually flexes the knee.
  • If quadriceps (anterior thigh) prevents knee flexion, gastrocnemius flexes the ankle, causing plantar flexion.
• Categories of Muscle Action
• Prime Mover (Agonist):
  • Muscle that produces most of force during joint action.
• Synergist:
  • Muscle that aids prime mover.
• Antagonist:
  • Muscle that opposes prime mover.
    • Often prevents overextension of joint.
• Fixator
  • Prevents a bone from moving.
    • Rhomboids prevents scapula from moving.
• For elbow flexion:
  • Prime mover-brachialis.
  • Synergist-biceps brachii.
  • ANtagonist-triceps brachii.
  • Fixator-rhomboids (hold scapula in place).
• Naming
• Latin names.
• Describes distinctive aspects of the structure, location, or action of a muscle.
• i.e - depressor labii inferioris. (Depressing the inferior part of labii)

• Muscles of Facial Expression
• Muscles of facial expression attach dermis and subcutaneous tissues.
• Tense skin and produce facial expressions.
• Innervated by facial nerve (CN VII)
• Paralysis cause face to sag.
• Found in scalp, forehead, around the eyes, nose, and mouth, and in the neck.

• Muscles of Chewing and Swallowing
• Extrinsic muscles of the tongue (Table 10.2):
  • Tongue is very agile organ.
  • Pushes food between molars for chewing (mastication).
  • Forces food into the pharynx for swallowing (deglutition).
  • Crucial importance to speech.
• Intrinsic muscle of tongue:
  • Vertical, transverse, and longitudinal fascicles.

• Muscles of Chewing
• 4 pairs of muscles produce biting and chewing movements of mandible.
  • Depression: to open mouth
  • Elevation: biting and grinding
  • Protraction: incisors can cut
  • Retraction: make rear teeth meet
  • Lateral and medial excursion: grind food.

1. Temporalis
2. Masseter
3. Medial pterygoid
4. Lateral pterygoid

• Innervated by mandibular nerve, a branch of the trigeminal (CN V)
• Muscles Acting on the Head
• Attachments:
  • Inferior: vertebral column, thoracic cage, and pectoral girdle.
  • Superior: cranial bones.
• Actions:
  • Flexion (tipping head forward)
    • Sternocleidomastoid
    • Scalenes
  • Extension (holding head erect)
    • Trapezius
    • Splenius capitis
    • Semispinalis capitis

• Muscles of Respiration
• Breathing requires use of muscles enclosing thoracic cavity

1. Diaphragm

• Muscular dome between thoracic and abdominal cavities.
• Contraction flattens diaphragm.
• Diaphragm rises when relaxes.

1. External intercostals

• Elevate ribs.
• Expand thoracic cavity.
• Create partial vacuum causing inflow of air.

1. Internal intercostals

• Depresses and retracts ribs.
  Compresses thoracic cavity.
• Expelling air.
• Muscles that Support the Anterior Abdominal Wall
• External abdominal oblique:
  • External layer of lateral abdominal muscles.
  • Supports viscera, breathing, unilateral contraction causes contralateral rotation (twist) of waist.
• Internal abdominal oblique:
  • Intermediate layer of lateral abdominal muscles.
  • Unilateral contraction causes ipsilateral rotation (bend) of waist.
• Transverse abdominal:
  • Deepest of lateral abdominal muscles.
  • Horizontal fibres.
  • Compresses abdominal contents.
  • Similar action to the external oblique.
• Rectus abdominis:
  • Flexes lumbar vertebral column.
  • Produces forward bending at waist.
  • Extends from sternum to pubis.
  • Segments (“six pack”).
• Lateral Abdominal Muscles

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• Muscles of the Anterior Abdominal Wall

• Muscles of the Back
• Actions of back muscles involve:
  • Extension, rotation, lateral flexion of vertebral column.
  • Upper limb movement.
• Most prominent superficial back muscles:

1. Latissimus dorsi
2. Trapezius

• Muscles Acting on Vertebral Column
• Deep muscles of the back:
• Erector spinae

1. Iliocostalis
2. Longissimus
3. Spinalis

• From cranium to sacrum.
• Extension and lateral flexion of vertebral column (sitting and standing erect, straighten back after one bends at waist).
• Muscles Acting on the Shoulder
• Posterior Compartment of Pectoral Girdle
  • Trapezius
  • Levator Scapulae
  • Rhomboids

• Muscles Acting on the Shoulder
• Anterior compartment of pectoral girdle
• Pectoralis minor
  • Ribs 3 to 5 coracoid process of scapula
  • Draws scapula laterally
• Serratus anterior
  • All ribs to medial border of scapula
  • Draws scapula laterally and forward
  • Prime mover for reaching and pushing

Muscles Acting on the Shoulder

• A group of muscles attach on the axial skeleton and also on clavicle or scapula
• Scapula loosely attached to thoracic cage
  • Capable of great movement
  • Rotation, elevation, depression, protection, retraction
• Clavicle braces the shoulder and moderates movement

Muscles Acting on the Shoulder

• Latissimus Dorsi
• Trapezius
• Deltoid
• Rhomboids
• Supraspinatus
• Infraspinatus
• Teres minor
• Erector spinae

Muscles Acting on the Arm

• 9 muscles cross shoulder joint and attach to humerus
• 2 axial muscles attaching on axial skeleton

1. Pectoralis major:

• Flexes, adducts, medially rotates humerus

1. Latissimus dorsi:

• Adducts and medially rotates humerus
• 7 muscles with scapular attachments

1. Deltoid

• rotates and abducts arm
• Intramuscular injection site

1. Teres major

• Extension and medial rotation of humerus

1. Coracobrachialis

• Flexes and medially rotates arm
• Remaining 4 = rotator cuff,
  • Reinforce shoulder joint

Muscles Acting on the Arm

Rotator Cuff Muscles

• Acronym “SITS muscles”
  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis
• Tendons merge with joint capsule of shoulder as cross on route to humerus
  • Holds head of humerus into glenoid cavity
  • Supraspinatus tendon easily damaged

Muscles Acting on Elbow and Forearm

• Elbow and forearm capable of Flexion, Extension, Pronation, Supination
• Carried out by muscles in both brachium (arm) and anytebrachium, (forearm)
  • Elbow Flexors: Anterior
    • Brachialis (prime mover)
    • Biceps brachii (synergistsic flexor)
    • Brachioradialis (synergistic flexor)
  • Elbow Extensor: Posterior
    • Triceps brachii

Actions of the Rotator Muscles on the Forearm

Supinator:

• Supinates forearm

Pronator quadratus:

• Pronates forearm

Pronator teres:

• Supports pronator quadartus in pronation

Flexor Muscles Acting on the Hand

Flexors

• Flexor carpi radialis
• Flexor carpi ulnaris

Extensor Muscles Acting on the Hand

Extensors

• Extensor digitorum
• Extensor carpi radialis longus
• Extensor carpi ulnaris

Overview

Muscles of thehip and lower limb

Muscles Acting on the Hip and Lower Limb

• Bodys largest muscles found in lower limb
• For strength needed to stad, maintain balance, walk, and run
• Several cross and act on two or more joints

Muscles Acting on Hip and Femur:

Anterior muscles of hip:

1. Iliacus

• Flexes thigh at hip
• I;iacus portion arises from iliac crest and fossa

1. Psoas major

• Flexes thigh at hip
• Arises from lumbar vertebrae
• Common tendon on femur

Muscles Acting on the Hip and Femur

Lateral and posterior muscles of hip

1. Gluteus maximus

• Forms mass of the buttock
• Prime hip extensor
• Provides most of lift when you climb stairs

1. Gluteus medius and minimus

• Abduct and medially rotate thigh

Muscles Acting on the Hip and Femur

• Medial (adductors) of thigh:

1. Adductor brevis
2. Adducytor longus
3. Adductor magnus
4. Gracilis
5. pectineus

Muscles Acting on Knee and Leg

• Amnteiro (extensor) of thigh
• Contains large quadriceps femoris muscle
  • Prime mover of knee extension
  • Most powerful muscle in body
• 4 heads- rectus femoris, vastus lateralis, vastus medialis, and vasrus intermedius
  • Converge on single (patellar) tendon
  • Extends to patella
  • Continues as patellar ligament to attach attach to tibial tuberosity
• Sartorius: longest muscle in the body

Muscles Acting on Knee and Leg

• Psoterioir (knee flexor) compartment of thigh
  • Contains hamstring muscles
  • Lateral to medial:

1. Biceps femoris
2. Semitendinosus
3. Semimebranosus

Muscles Acting on Foot

Posteriori compartment

• Superficial group:

1. Gastrocnemius:

• Plantar flexes foot
• Flexes knee

1. Soleus:

• Plantar flexes foot

1. Plantaris:

• Weak synergist

Muscles Acting on the Foot

Anterior compartment of the leg:

• Tibialis anterior
  • Dorsiflexes the foot at the ankle
  • Helps resist backward tipping

Common Athletic Injuries

• Muscles an tendons vulnerable to sudden and intense stress
• Common injuries include:
  • Compartment syndrome
  • Pulled hamstings
  • Pulled groin
  • Rotator cuff injury

Anatomy of the Skin

Integumentary System

Consists of:

1. Skin and accessory organs
2. Hair
3. Nails
4. Cutaneous glands

• Most vulnerable organ
  • Exposed to radiation, trauma, infection, injurious chemicals

Structure of Skin and Subcutaneous Tissue

The Epidermis

• Kertinized stratified squamous epithelium
  • Includes dead cells at skin surface packed with tough keratin protein
• avascualr - dpends on diffusion of nutrients from underlying connective tissue
• Spare nerve endings for touch and pain

Layers of the Epidermis

1. Stratum basale (deepest epidermal layer)

• Single layer of stem cells and keratinocytes

1. Stratum spinosum

• Several layers of keratinocytes
• Named for appearance of cells after histological preparation (spiny)

1. Stratum ghranulosukm

• 3-5 layers of flat kertinocytes
• Cells contain dark-staining keratohyalin

1. Stratum lucidum

• Thin, pale layer found only in thick skin
• Keratinocytes packed with clear protein

1. Stratum corenum (surface layer)

• Several layers (up to 30) of dead, scaly, keratinized cells
• Reisys abradion, penetration, water loss

Layers of Dermis

Wavy, conspicuous boundrary with the superficial epidermis

• Dermal papillae- upwards, finger-like extensions of dermis
• Epidermal ridges are downward waves of dermis
  • Prominent waves on fingers produce friction ridges (fingerpirnts)
    • Papillary layer - superficial layer of dermis
      • Thin zone near dermal papilla
      • Allows for mobility of leukocytes
      • Rich in small blood vessels
    • Reticular zone- deeper and thicker layer of dermis
      • Dense, irregular connective tissue
      • Stretch marks (striae) - tears in collagen fibers caused by stretching of skin.

Hypodermis

• Common site of drug injection due to many blood vessels
• Subcutaneous tissue
  • Pads body and binds skin to underlying tissues
• Subcutaneous fat
  • Energy reservoir
  • Thermal insulation
  • Thicker in women, thinner in infants, elderly

Skin Colour

Melanin: produced by melanocytes, accumulates in keratinocytes

Darker skin

• Melanocytes produce more melanin and breaks down more slowly
• Melanin granules more spread out in keratinocytes and seen throughout epidermis

Lighter Skin

• Melanin clumped near keratinocyte nucleus
• Little melanion seen beyond stratum basale

Anatomy of Hair, Nails, and Glands

Structure of the Hair and its Follicle

• Mostly dead, keratinized cells
  • Pliable soft keratin makes up starum coreneu, of skin
  • Compact hard keratin makes up hair and nails
• 3 zones
  • Bulb
  • Root
  • Shaft

Follicle = diganole tube that contains hair root

Hair Colour and Texture

• Texture from cross sectional shape of hair
  • Straight = round
  • Wavy = oval
  • Curly = flat
• Colour from pigment granules in cortex
  • Brown/black = eumelanin
  • Red= pheomelanin
  • Blond = some pheomelanin and little eumelanin
  • Gray/white = little or no melanin

• Nails
• Clear, hard derivatives of the stratum corneum.
  • Thin, dead cells packed with hard keratin.
• Nail plate (hard part of nail):
  • Free edge
  • Nail body
  • Nail root
• Nail fold
• Nail groove
• Nail bed
• Nail matrix - growth zone
• Eponychium (cuticle)
• Cutaneous Glands