Skeletal Muscle Classification Quiz

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Questions and Answers

What is the primary function of the extrinsic eye muscles?

Produce tears to lubricate the eye

Regulate pupil size

Control the shape of the lens

Control the position of the eye (correct)

Which muscle group is responsible for moving food around the cheeks?

Buccinator (correct)

Masseter

Temporalis

Orbicularis oris

Which nerve primarily supplies the muscles of facial expression?

Oculomotor nerve

Facial nerve (correct)

Trigeminal nerve

Hypoglossal nerve

What distinguishes the muscles of the pharynx?

They initiate the process of swallowing. Signup and view all the answers

Which extrinsic eye muscle is innervated by the Trochlear nerve?

Superior oblique Signup and view all the answers

What type of muscle is characterized by fibers arranged parallel to the long axis of the muscle?

Parallel muscle Signup and view all the answers

Which type of muscle has fibers that are arranged at an angle to the tendon?

Pennate muscle Signup and view all the answers

What term describes the muscle that produces a particular action?

Agonist Signup and view all the answers

Which type of muscle is known for its ability to open and close body openings?

Sphincters Signup and view all the answers

What is the point of attachment called that remains fixed during muscle contraction?

Origin Signup and view all the answers

In which type of pennate muscle do the fibers branch around the tendon?

Multipennate Signup and view all the answers

Which muscle is specifically identified as a prime mover in a flexion action?

Biceps brachii Signup and view all the answers

What term refers to muscles that oppose the action of the agonist?

Antagonists Signup and view all the answers

Which muscle is NOT part of the rotator cuff?

Teres major muscle Signup and view all the answers

What is the primary function of the gluteus maximus muscle?

Extension and lateral rotation at the hip Signup and view all the answers

What do the iliopsoas muscles consist of?

Psoas major and iliacus Signup and view all the answers

Which of the following muscles is NOT a part of the adductor group?

Gluteus maximus Signup and view all the answers

What is the main role of the pelvic girdle?

Permits minimal movement and stability Signup and view all the answers

Which muscle is the major extensor of the elbow?

Triceps brachii Signup and view all the answers

What is the role of pronator teres and supinator muscles?

Rotate the radius Signup and view all the answers

Which of the following muscles is primarily responsible for flexing the wrist and abducting it?

Flexor carpi radialis Signup and view all the answers

What structures stabilize the tendons of extensor muscles in the wrist?

Extensor retinaculum Signup and view all the answers

Carpal tunnel syndrome is primarily caused by the compression of which nerve?

Median nerve Signup and view all the answers

Which muscle is NOT a part of the rotator cuff?

Teres major Signup and view all the answers

Which of the following statements about intrinsic muscles of the hand is true?

They include the lumbricals and interossei. Signup and view all the answers

What type of connective tissue structure stabilizes tendons of flexor muscles?

Flexor retinaculum Signup and view all the answers

What is the primary function of the rectus abdominis muscle?

Flexes the vertebral column Signup and view all the answers

Which muscle is primarily responsible for lateral rotation of the shoulder?

Infraspinatus Signup and view all the answers

What muscle is the main muscle of inspiration?

Diaphragm Signup and view all the answers

Which muscle is considered the most superficial among the oblique muscles?

External oblique Signup and view all the answers

What is the primary action of the serratus anterior muscle?

Stabilizes the scapula Signup and view all the answers

Which muscle assists the deltoid for the first 15° of arm abduction?

Supraspinatus Signup and view all the answers

What area does the perineum encompass?

Anteriorto the anus Signup and view all the answers

Which of the following muscles is part of the rotator cuff?

Supraspinatus Signup and view all the answers

What is the function of the external urethral sphincter?

Controls urine movement through the urethra Signup and view all the answers

Where does the pectoralis major muscle originate?

Costal cartilage of ribs Signup and view all the answers

Which muscle primarily flexes the elbow?

Biceps brachii Signup and view all the answers

What is the main role of the pelvic floor muscles?

Support organs in the pelvic cavity Signup and view all the answers

Which muscle is deep to the external oblique?

Internal oblique Signup and view all the answers

What type of movement is the diaphragm primarily responsible for?

Respiration Signup and view all the answers

How long does it take for a keratinocyte to transition from the stratum germinativum to the stratum corneum?

15-30 days Signup and view all the answers

What type of perspiration involves the loss of interstitial fluid by evaporation?

Insensible perspiration Signup and view all the answers

What substance is a precursor for vitamin A found in the skin?

Carotene Signup and view all the answers

Which condition is characterized by a bluish skin discoloration due to low blood oxygen levels?

Cyanosis Signup and view all the answers

What causes xerosis, or dry skin?

Damage to stratum corneum Signup and view all the answers

Melanin production determines skin color primarily through what mechanism?

Melanin production rate Signup and view all the answers

What can result from a deficiency of vitamin D in children?

Rickets Signup and view all the answers

Which type of skin cancer is characterized as malignant melanoma?

Malignant melanoma Signup and view all the answers

Which of the following causes skin color to darken when exposed to sunlight?

Increased melanin production Signup and view all the answers

What effect does immersion in a hypotonic solution have on the skin?

It leads to hydration and wrinkling. Signup and view all the answers

What percentage of body weight does the integument represent?

16% Signup and view all the answers

What is the primary component of the outer layer of the cutaneous membrane?

Epithelial tissue Signup and view all the answers

Which structure is considered an accessory structure of the integument?

Hair Signup and view all the answers

Which layer of the epidermis is primarily responsible for the generation of new skin cells?

Stratum germinativum Signup and view all the answers

In which layer of the epidermis do keratinocytes begin to die and form a protective barrier?

Stratum granulosum Signup and view all the answers

What key protein do keratinocytes produce that is essential for the skin's protective barrier?

Keratin Signup and view all the answers

What type of skin has five layers of keratinocytes?

Thick skin Signup and view all the answers

Which cells in the epidermis are responsible for the sensation of touch?

Merkel cells Signup and view all the answers

What distinguishes the stratum lucidum from other layers of the epidermis?

It is found only in thick skin. Signup and view all the answers

Which of the following is NOT a function of the integument?

Producing hormones Signup and view all the answers

Which layer is considered the 'horny layer' of the skin?

Stratum corneum Signup and view all the answers

What is the main function of Langerhans cells in the skin?

Immune response Signup and view all the answers

Which factor contributes to the thickness of the stratum corneum in thick skin?

Number of cell layers Signup and view all the answers

What role does keratinization play in skin health?

It forms a protective barrier. Signup and view all the answers

What characterizes insensible perspiration?

It consists of interstitial fluid lost by evaporation. Signup and view all the answers

What is the primary function of melanin in the skin?

To protect the skin from ultraviolet rays. Signup and view all the answers

What condition is a result of overproduction of bilirubin in the body?

Jaundice Signup and view all the answers

What is the primary cause of xerosis?

Damage to the stratum corneum. Signup and view all the answers

Which skin color abnormality is associated with loss of melanocytes?

Vitiligo Signup and view all the answers

What is the role of epidermal ridges?

To strengthen the bond between epidermis and dermis. Signup and view all the answers

What vitamin is produced by epidermal cells in response to UV radiation?

Cholecalciferol (Vitamin D3) Signup and view all the answers

Which condition can cause skin to appear pale?

Vasoconstriction of capillaries Signup and view all the answers

What happens to keratinocytes as they move from the stratum germinativum to stratum corneum?

They transition and eventually die as they reach the surface. Signup and view all the answers

What is the effect of immersion in a hypertonic solution on the skin?

It causes dehydration due to osmosis. Signup and view all the answers

What is the primary function of the keratin produced in the stratum granulosum?

To form a protective layer covering the epidermis Signup and view all the answers

Which layer of the epidermis is characterized as the 'clear layer' and is only found in thick skin?

Stratum lucidem Signup and view all the answers

What role do melanocytes play within the stratum germinativum of the epidermis?

They produce melanin pigment Signup and view all the answers

How many layers of keratinocytes are typically found in thick skin?

5 Signup and view all the answers

Which type of cells in the stratum spinosum are involved in the immune response?

Langerhans cells Signup and view all the answers

What process describes the formation of a protective layer of dead cells filled with keratin?

Keratinization Signup and view all the answers

In which part of the integumentary system are exocrine glands primarily located?

Dermis Signup and view all the answers

What is the main characteristic of the epidermis that affects its nutrient supply?

Avascular Signup and view all the answers

Which layer of the epidermis is responsible for the initial cell division?

Stratum germinativum Signup and view all the answers

Which factor influences the thickness of the stratum corneum?

Location of the skin on the body Signup and view all the answers

What is primarily produced in the stratum granulosum that aids in waterproofing the skin?

Keratin Signup and view all the answers

Which of the following is NOT a function of the integumentary system?

White blood cell production Signup and view all the answers

What component of the integument forms the outermost barrier against environmental damage?

Epidermis Signup and view all the answers

What is a likely consequence of a deficiency in vitamin D?

Weakened bones Signup and view all the answers

Study Notes

Classification of Skeletal Muscles

Muscles can be classified based on fascicle organization: parallel, convergent, circular, pennate.
Parallel muscles have fibers parallel to the long axis of the muscle, like the sartorius.
Convergent muscles have a broad area that converges on the attachment site, like the pectoralis muscles.
Circular muscles, also called sphincters, open and close to guard openings of the body, like the orbicularis oris.
Pennate muscles have fascicles forming an angle with the tendon, and can be unipennate, bipennate, or multipennate.

Origin, Insertion, and Action

Origin is the fixed point of attachment of a muscle.
Insertion is the moving point of attachment of a muscle.
Most muscles originate or insert on the skeleton.
Origin is usually proximal to insertion (there are exceptions), but there are exceptions to this rule.
Action is the movement produced by muscle contraction and usually involves pulling the insertion toward the origin (there are exceptions).

Types of Muscles Based on Action

An agonist (prime mover) produces a particular action.
A synergist assists a larger agonist and helps stabilize the origin of the agonist (fixator).
An antagonist opposes the action of the agonist.
Agonists and antagonists work as pairs, one contracting while the other relaxes, allowing movement.

Naming Skeletal Muscles

The term "muscle" is included in the correct names of muscles except for platysma and diaphragm.
Naming can be determined by location, origin and insertion, fascicle organization, relative position, or structure characteristics.

Muscles of Head & Neck

Extrinsic eye muscles originate on the orbital surface and insert on the sclera of the eyeball to control eye position.
Muscles of the tongue, named with "glossus" at the end.
Muscles of the pharynx begin the swallowing process.
Muscles of the neck are divided into anterior, posterior, and lateral groups.

Muscles of Facial Expression

Are mimetic, supplied by the Facial Nerve (VII).

Muscles of Facial Expression: Specific Examples

Occipitofrontalis (Epicranius) has frontal and occipital bellies separated by the epicranial aponeurosis (galea aponeurotica).
Orbicularis oculi closes the eye and produces blinking.
Orbicularis oris constricts the mouth opening.
Buccinator moves food around the cheeks.

Muscles of Mastication

Masseter is the strongest jaw muscle.
Temporalis helps lift the mandible.
Buccinator moves food around the cheeks.
Pterygoids (medial and lateral) are supplied by the Trigeminal Nerve.

Extrinsic Muscles of the Eye

Four recti muscles (superior, inferior, medial, lateral) are responsible for specific eye movements.
Two oblique muscles (superior and inferior) aid in eye movements.
All muscles are supplied by the Oculomotor Nerve (III) except the lateral rectus (VI) and the superior oblique (IV).

Muscles of the Neck: Sternocleidomastoid

This muscle has an exception: the origin is distal to the insertion, and the insertion is pushed away from the origin.

Muscles of the Abdominal Wall

Oblique muscles compress underlying structures and rotate the vertebral column.
Rectus muscles flex the vertebral column and oppose the erector spinae muscles of the vertebral column.

Oblique Muscles: Details

External oblique is the most superficial, fibers run downward and medially.
Internal oblique underlies the external oblique, fibers run upward and medially.
Transversus abdominis is the deepest, fibers run horizontally.

Rectus Group: Rectus Abdominis

Located between the xiphoid process and the symphysis pubis.
Separated in the middle line by linea alba.
Divided transversely by tendinous inscriptions.

Rectus Group: Diaphragm

Divides the thoracic and abdominal cavities.
Main muscle of inspiration.

Muscles of the Pelvic Floor

Support organs of the pelvic cavity and control movement of urine and stool.
Flex the sacrum and the coccyx.

Perineum

Area of skin anterior to the anus extending to the vaginal opening (female) or base of the testicles (male).
Rich in nerve endings.
Site of episiotomy.

Appendicular Muscles

Muscles of the pectoral girdle: Trapezius, deltoid, latissimus dorsi, rhomboids, levator scapulae, serratus anterior, and intercostals.
Muscles of the upper limbs: Biceps brachii, triceps brachii, brachialis, pronator teres, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, palmaris longus, flexor carpi radialis, flexor digitorum superficialis, flexor carpi ulnaris, extensor carpi ulnaris.
Muscles of the pelvic girdle: Gluteus maximus, gluteus medius, adductor magnus, iliopsoas, pectineus, tensor fascia latae, semitendinosus, semimembranosus, gracilis, sartorius.
Muscles of the lower limbs: Biceps femoris, rectus femoris, vastus lateralis, vastus medialis, gastrocnemius, soleus, fibularis longus, tibialis anterior, extensor digitorum longus.

Muscles of the Pectoral Girdle

Trapezius is superficial, covers the back and neck, and inserts on the clavicle and scapular spine.
Rhomboids and levator scapulae are deep to the trapezius, originate on cervical and thoracic vertebrae, and insert on the medial scapular border.
Serratus anterior is on the chest, originates along the ribs and inserts on the anterior scapular margin.

Muscles Move Upper Limbs

Muscles move the arm: pectoralis major, latissimus dorsi.
Muscles move the forearm: biceps brachii, triceps brachii, brachialis.
Muscles move the hand and fingers: pronator teres, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, palmaris longus, flexor carpi radialis, flexor digitorum superficialis, flexor carpi ulnaris.

Muscles Move the Arm: Details

Pectoralis major adducts and medially rotates the shoulder, and flexes the shoulder.
Latissimus dorsi extends the shoulder.

Muscles Move the Arm: Rotator Cuff

Deltoid is the major abductor of the arm.
Supraspinatus assists the deltoid for the first 15 degrees of abduction.
Infraspinatus and teres minor produce lateral rotation at the shoulder.
Subscapularis and teres major produce medial rotation at the shoulder.

Rotator Cuff: Details

Composed of four muscles: subscapularis, supraspinatus, infraspinatus, and teres minor.
Originate from the scapula.
Combine to form a "cuff" over the humerus head.
Form a single tendon that inserts on the greater tubercle of the humerus.
Help lift and rotate the arm and stabilize the ball of the shoulder within the joint.

Rotator Cuff Tears

Causes include acute injuries and repetitive overhead work.
Common cause of pain and disability in adults.

Muscles Move the Forearm & Hand: Flexors and Extensors

Flexors are mainly located on the anterior and medial surfaces of the arm and forearm.
Extensors are mainly located on the posterior and lateral surfaces of the arm and forearm.

Muscles Move the Forearm: Origin

Muscles originate from the scapula (biceps brachii, triceps brachii - long head), humerus, or the forearm bones.

Flexors of the Forearm

Biceps brachii is the major flexor of the elbow, originating on the scapula with two heads (long and short) and inserting on the radial tuberosity.
Brachialis and brachioradialis assist the biceps brachii as synergists.

Extensors of the Forearm

Triceps brachii is the major extensor of the elbow, originating on the scapula and humerus with three heads (long, medial, and lateral), and inserting on the olecranon.

Pronators & Supinators of the Forearm

Pronator teres and supinator originate on the humerus and ulna, insert on the radius, and rotate the radius (pronation and supination).

Muscles Move the Hand & Fingers

Extrinsic muscles are located outside the hand in the forearm, with only tendons crossing the wrist.
Intrinsic muscles are located entirely within the hand.

Extrinsic Muscles of the Hand

Extrinsic muscles move the hand and fingers.

Flexors of the Hand

Flexor carpi radialis flexes and abducts the wrist.
Palmaris longus flexes the wrist.
Flexor carpi ulnaris flexes and adducts the wrist.

Extensors of the Hand

Extensor carpi radialis longus and brevis extend and abduct the wrist.
Extensor carpi ulnaris extends and adducts the wrist.

Intrinsic Muscles of the Hand

Intrinsic muscles are located within the hand.

Tendon Sheaths

Wide bands of connective tissue that stabilize tendons:
Extensor retinaculum on the posterior wrist stabilizes extensor muscles,
Flexor retinaculum on the anterior wrist stabilizes flexor muscles.

Carpal Tunnel Syndrome

Thickening of the flexor retinaculum narrows the carpal tunnel, compressing the median nerve.
Leads to numbness, pain, and impaired nerve function.

Rotator Cuff Muscles: Correct Identification

The rotator cuff consists of:
- Subscapularis
- Teres major
- Supraspinatus
- Teres minor
- Infraspinatus

Muscles of the Pelvic Girdle

The pelvic girdle is tightly bound to the axial skeleton, allowing for limited movement and few muscles.

Muscles Move Lower Limbs

Muscles move the thigh, leg, foot, and toes.

Muscles Move the Thigh

Gluteal muscles cover the lateral surface of the ilium.
Lateral rotators extend from the acetabulum to the greater trochanter.
Adductors are situated along the medial aspect of the thigh.
Iliopsoas muscle is a group of two muscles working together.

Gluteal Muscles: Details

Gluteus maximus is the largest and most posterior gluteal muscle, inserting on the iliotibial tract and responsible for hip extension and lateral rotation.
Gluteus medius and minimus are anterior to the gluteus maximus, inserting on the greater trochanter of the femur.
Tensor fascia latae works with the gluteus maximus and stabilizes the iliotibial tract.

Adductors: Details

Adductor magnus performs adduction, flexion, and medial rotation (superior part) and adduction, extension, and lateral rotation (inferior part).
- Adductor longus
- Adductor brevis
- Pectineus
- Gracilis
Gracilis adducts, flexes, and medially rotates the thigh.

Iliopsoas Muscle: Details

Consists of two hip flexors: psoas major and iliacus.
Originates on the lumbar vertebrae and iliac fossa.
Share one tendon.
Inserts on the lesser trochanter.

Integumentary System

Largest system of the body
16% of body weight
1.5 to 2 m2 surface area

Components

Cutaneous membrane (skin)
Accessory structures: hair, mammary glands, ceruminous glands, nails

Cutaneous Membrane

Outer epidermis (epithelium)
Inner dermis (connective tissue)

Accessory Structures

Derived from embryonic epidermis
Located in dermis
Project through the skin surface

Blood & Nerve Supply

Blood supply: blood vessels in the dermis
Nerve supply: sensory receptors for pain, temperature, touch, and pressure

Functions

Protects underlying tissues and organs
Maintains body temperature
Excretes water, salts, and organic wastes
Synthesizes vitamin D3
Stores lipids
Sensation: pain, temperature, touch, pressure

Epidermis

Stratified squamous epithelium
Avascular: nutrients and O2 diffuse from capillaries in the dermis
Keratinocytes: most abundant cells; organized in layers; contain large amounts of keratin

Types of Skin

Thin skin: most of the body, 4 layers
Thick skin: palms and soles, 5 layers

Layers (Strata) of the Epidermis

Five strata of keratinocytes in thick skin from basal lamina to free surface:
- Stratum germinativum
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Four strata of keratinocytes in thin skin from basal lamina to free surface:
- Stratum germinativum
- Stratum spinosum
- Stratum granulosum
- Stratum corneum

Stratum Germinativum (Basale)

The "germinative layer"
Most basal layer
1–3 layers of cells
Many germinative (stem - basal) cells
Attached to basement membrane by hemidesmosomes

Cells of Stratum Germinativum

Basal (germinative) keratinocytes: dominant cells, replace lost cells
Merkel cells: found in hairless skin, touch receptors
Melanocytes: produce melanin pigment, migrate from the dermis to the stratum germinativum of the epidermis

Stratum Spinosum

The "spiny layer"
Produced by division of stratum germinativum
8–10 layers of keratinocytes bound by desmosomes

Cells of Stratum Spinosum

Keratinocytes: some continue to divide, increasing thickness of epithelium; shrink until cytoskeleton sticks out (spiny)
Langerhans cells: dendritic cells; skin macrophages; active in immune response (antigen-presenting cells)

Stratum Granulosum

The "grainy layer"
3–5 layers of keratinocytes
Cells stop dividing and start producing:
- Keratin: tough, fibrous protein; covers the epidermis; makes up hair and nails
- Keratohyalin: dense protein granules; cross-link keratin fibers

Cells of Stratum Granulosum

Keratinocytes: do not divide; produce protein fibers; nuclei and organelles disintegrate; dehydrate and die; create tightly interlocked layer of keratin surrounded by keratohyalin

Stratum Lucidum

The "clear layer"
ONLY in thick skin
3–5 layers of keratinocytes
Keratinocytes: dead; flat; dense; filled with keratin

Stratum Corneum

The "horny layer"
Exposed surface of skin
15 to 30 layers of keratinized dead cells
Significantly thicker in thick skin
Water resistant
Sheds and is replaced every 2 weeks

Keratinization (Cornification)

Forming a protective layer of dead cells filled with keratin
Occurs on all exposed skin surfaces except eyes

Skin Life Cycle

Takes 15–30 days for a keratinocyte to move from stratum germinativum to stratum corneum

Perspiration

Elimination of fluid through skin pores
Insensible perspiration: interstitial fluid lost by evaporation through the stratum corneum (500 ml/day)
Sensible perspiration: water (sweat) excreted by sweat glands (variable amount)

Water Loss Through Skin

Dehydration results from:
- Damage to stratum corneum, e.g., burns and blisters (insensible perspiration)
- Immersion in hypertonic solution, e.g., seawater (osmosis)
Xerosis = dry skin

Water Gain Through Skin

Hydration: results from immersion in hypotonic solution, e.g., freshwater (osmosis); causes stretching and wrinkling of skin

Skin Color (Complexion)

Depends on:
- Pigments:
  - Carotene
  - Melanin
- Blood circulation:
  - RBCs

Carotene

Orange-yellow pigment
Found in orange vegetables (carrots)
Accumulates in epidermal cells and fatty tissues of the dermis
Precursor of vitamin A

Melanin

Brown-black pigment
Produced by melanocytes in stratum germinativum
Stored in transport vesicles (melanosomes)
Transferred to keratinocytes
Skin color depends on melanin production, not number of melanocytes
Protects skin from sun damage by UV rays

Freckles & Nevi

Freckles: small pigmented areas, mainly on the face, increase with sun exposure
Nevus (mole): benign melanoma

Capillaries & Skin Color

Hemoglobin pigment in RBCs contributes to skin color:
- Vasodilation: red skin
- Vasoconstriction: pale skin
Pallor: skin and mucous membranes, usually associated with anemia (low hemoglobin concentration)

Cyanosis

Bluish skin discoloration
Due to severe hypoxia (decreased blood O2)
Causes: extreme cold, cardiovascular disease, respiratory disease

Common Abnormal Skin Colors

Jaundice: yellow color, buildup of bilirubin pigment (hyperbilirubinemia)
Vitiligo: autoimmune disease, loss of melanocytes, loss of skin color

Skin & Vitamin D

Epidermal cells produce cholecalciferol (vitamin D3): requires UV radiation from sunlight
Liver and kidneys activate vitamin D (calcitriol)
Function: enhances absorption of Ca and P from intestine

Vitamin D Deficiency

Children: rickets
Adults: osteomalacia

Malignant Skin Tumors

Basal Cell Carcinoma
Squamous Cell Carcinoma
Malignant Melanoma

Epidermal Ridges & Dermal Papillae

Strengthen the bond between epidermis and dermis
Epidermal ridges:
- Formed by stratum germinativum
- Fingerprints
Dermal papillae:
- Project through epidermal ridges
- Increase the area of basal lamina

Do identical twins have identical fingerprints?