Anatomy: Generalities, Head, Neck

Questions and Answers

What is a primary characteristic that distinguishes cardiac muscle from skeletal muscle?

Cardiac muscle can be voluntarily controlled.

Cardiac muscle contains multiple nuclei per cell.

Cardiac muscle primarily functions to allow for body movement.

Cardiac muscle features branching, striated cells with intercalated discs. (correct)

What type of stimulation primarily governs the contractions of cardiac muscle?

Intrinsic myogenic stimulation with modifications from the autonomic nervous system. (correct)

Hormonal stimulation solely from adrenal glands.

Electrical stimulation from external devices.

Voluntary stimulation through conscious control.

Which of the following correctly describes the location of cardiac muscle?

It is located exclusively in the heart and adjacent large vessels. (correct)

It is primarily found in the limbs and head.

It is distributed throughout the torso and abdomen.

It forms the walls of blood vessels.

Which of these features is common to all types of muscle but presents differently in cardiac muscle?

Striated appearance. Signup and view all the answers

How do contractions of cardiac muscle primarily differ from those of skeletal muscle?

Cardiac muscle contractions are slower, rhythmic, and involuntary. Signup and view all the answers

Which of the following muscles is NOT developed from the branchial arches?

Longissimus Signup and view all the answers

Which cranial nerve primarily innervates the muscles arising from the first branchial arch?

Trigeminal nerve Signup and view all the answers

Which of the following muscles is innervated by the glossopharyngeal nerve?

Stylopharyngeus Signup and view all the answers

What type of muscle is classified as epaxial?

Skeletal muscles located dorsal to the vertebral column Signup and view all the answers

Which statement about the branchiomeric musculature is correct?

The anterior belly of the digastric is innervated by the trigeminal nerve. Signup and view all the answers

What is a specific attachment point for the visceral fascia in the neck?

Hyoid bone Signup and view all the answers

Which fascia surrounds the cervical vertebral unit?

Prevertebral fascia Signup and view all the answers

What is the inferior attachment point of the visceral fascia?

Superior mediastinum Signup and view all the answers

Which of the following structures does NOT attach to the superior aspect of the visceral fascia?

Thyroid cartilage Signup and view all the answers

Which fascia lies deep to the deep investing fascia in the neck?

Visceral fascia Signup and view all the answers

What is the superior attachment point of the deep investing fascia?

Inferior border of mandible Signup and view all the answers

Which structure does the deep investing fascia NOT blend with?

Transverse processes of cervical vertebrae Signup and view all the answers

What forms the structure known as the Alar fascia?

Division of the anterior component of the prevertebral fascia Signup and view all the answers

Which of the following is NOT an inferior attachment of the deep investing fascia?

Inferior border of the hyoid bone Signup and view all the answers

Which anatomical landmark serves as an inferior attachment of the deep investing fascia?

Clavicles Signup and view all the answers

Which layer of the scalp is described as the 'dangerous layer' and why?

Loose areolar tissue, due to its potential space for infection spread Signup and view all the answers

What phenomenon explains why an incised wound that involves the first three layers of the scalp gapes if it is along the coronal plane?

The orientation of the fibers in the scalp layers Signup and view all the answers

Which characteristic of the 4th layer of the scalp contributes to diffuse bleeding?

It contains valveless veins allowing free communication of blood Signup and view all the answers

Why do clean wounds in the scalp heal more rapidly compared to other areas?

The vascular supply allows for increased delivery of nutrients Signup and view all the answers

What is the unique feature of the emissary veins in the scalp that impacts infection risk?

They connect superficial and deep venous systems in the scalp Signup and view all the answers

What is the primary action of the occipital belly of the occipitofrontalis muscle?

Moves the scalp on the skull Signup and view all the answers

Which nerve is responsible for innervating both the occipital belly and frontal belly of the occipitofrontalis muscle?

Facial nerve Signup and view all the answers

What is the action performed by the orbicularis oculi muscle?

Closes the eye tightly Signup and view all the answers

Which structure serves as the origin for the occipital belly of the occipitofrontalis muscle?

Highest nuchal line of occipital bone Signup and view all the answers

What is the insertion point for the orbicularis oculi muscle?

Skin around the margin of the orbit Signup and view all the answers

Which type of muscle contracts involuntarily and is influenced by the autonomic nervous system?

Smooth muscle Signup and view all the answers

Which cranial nerve innervates the muscles of facial expression?

Facial nerve Signup and view all the answers

What is a characteristic feature of skeletal muscles compared to smooth muscles?

Skeletal muscle has multiple nuclei Signup and view all the answers

Which muscle is exclusively innervated by the glossopharyngeal nerve?

Stylopharyngeus muscle Signup and view all the answers

Which type of muscle primarily supports functions like peristalsis and controlling blood vessel diameter?

Smooth muscle Signup and view all the answers

What differentiates cardiac muscle from other muscle types?

It has intercalated discs Signup and view all the answers

What is the primary control mechanism for skeletal muscle contractions?

Voluntary nervous system Signup and view all the answers

Which muscles are primarily innervated by the vagus nerve?

Brachial muscles of the fourth and sixth arches Signup and view all the answers

What is the primary function of cardiac muscle?

Pumps blood from the heart Signup and view all the answers

Which characteristic is unique to cardiac muscle cells?

Branched structure with intercalated discs Signup and view all the answers

How is the contraction of cardiac muscle stimulated?

By intrinsic myogenic activity Signup and view all the answers

What type of muscle is classified as striated due to its appearance under the microscope?

Both cardiac and skeletal muscle Signup and view all the answers

What distinguishes skeletal muscle from cardiac muscle?

Skeletal muscle is under voluntary control Signup and view all the answers

Where is cardiac muscle predominantly located?

Exclusively in the heart Signup and view all the answers

Which system primarily modifies the rate and strength of cardiac muscle contractions?

Autonomic nervous system Signup and view all the answers

Which type of muscle is NOT associated with the control mechanism involving the autonomic nervous system?

Skeletal muscle Signup and view all the answers

What percentage of a mixed nerve trunk is motor fibers?

60% Signup and view all the answers

What triggers muscle fiber degeneration during denervation?

Activation of atrophy-related signaling Signup and view all the answers

Disuse atrophy primarily results from what action?

Insufficient muscle use Signup and view all the answers

What effect does denervation have on skeletal muscles?

Rapid degeneration and activation of atrophy signaling Signup and view all the answers

What is the consequence of muscle disuse in the context of energy management?

Reduced energy demands of the body Signup and view all the answers

Which muscle groups should be emphasized for their importance in nerve supply?

Muscles of the upper and lower extremities, trunk, and neck Signup and view all the answers

What is the primary outcome of stopping muscle use?

Rapid muscle degeneration Signup and view all the answers

The presence of sympathetic fibers within a nerve trunk contributes to which of the following?

Regulation of involuntary actions Signup and view all the answers

What is a primary factor influencing the naming of muscles?

The depth or position of the muscle Signup and view all the answers

What term is used to describe a muscle that is positioned deep in relation to another muscle?

Profundus Signup and view all the answers

How are muscles typically named based on their function?

By the movement they produce Signup and view all the answers

Which of the following examples represents a muscle named for its action?

Flexor Digitorum Profundus Signup and view all the answers

What naming convention applies to the muscles in the chest region?

Pectoralis Signup and view all the answers

Which component is NOT typically considered in muscle nomenclature?

Color Signup and view all the answers

Which of the following is an example of a muscle named according to its size?

Pectoralis minor Signup and view all the answers

What aspect of a muscle's nomenclature is indicated by the term 'Brachii'?

Arm location Signup and view all the answers

Which of the following best describes intrinsic muscles?

They are found entirely within the body part upon which they act. Signup and view all the answers

What distinguishes extrinsic muscles from intrinsic muscles?

Extrinsic muscles have attachments both inside and outside the body part they act upon. Signup and view all the answers

Which disorder is characterized by sudden, uncontrollable jerky movements?

Chorea Signup and view all the answers

What is a common cause of hemiballismus?

Dysfunction in the central nervous system Signup and view all the answers

Myelitis refers to which of the following?

Inflammation of the spinal cord Signup and view all the answers

Which statement accurately describes the relationship between intrinsic and extrinsic muscles?

Both types can exist in the same body part. Signup and view all the answers

Which term describes the movements involving separate, strong, involuntary flinging motions?

Hemiballismus Signup and view all the answers

Which of the following best illustrates an intrinsic muscle's location?

The interosseous muscles of the hands Signup and view all the answers

Study Notes

Generalities of Muscles and Innervation

Cardiac Muscle
- Unique to the heart; involuntary muscle.
- Features branching striated cells, intercalated discs, and typically one nucleus per cell.
- Responsible for pumping blood; contraction is rhythmic and influenced by the autonomic nervous system.
Skeletal Muscle
- Comprises major gross muscles attached to the skeleton, enabling voluntary movement.
- Also known as striated muscle due to its appearance.
- Includes named muscles like biceps in the arm.
Smooth Muscle
- Involuntary muscle found in internal organs.

Branchial Arches and Musculature

Branchiomeric Musculature
- Muscles from first branchial arch innervated by the trigeminal nerve.
- Includes muscles of mastication and the anterior belly of the digastric muscle.

Cranial Nerves

Longest cranial nerve: Vagus Nerve.
Smallest muscle: Stapedius in the ear and Arrector Pili (causes goosebumps).

Muscle Classification

Epaxial Muscles
- Located dorsal to the vertebral column, includes transversospinalis, longissimus, and iliocostalis muscles.
Hypaxial Muscles
- Located ventral to the vertebral column; involves trunk and limb muscles, diaphragm, and abdominal muscles.

Muscle Roles During Movement

Prime Mover (Agonist)
- Main muscle responsible for a specific movement (e.g., triceps in forearm extension).
Antagonist
- Muscle opposing the action of the prime mover (e.g., triceps during elbow flexion when biceps are the prime mover).
Synergist
- Assists the prime mover in performing a specific action.
Fixator
- Stabilizes joints while movement occurs.

Muscle Anatomy

Origin
- The stable, proximal attachment of a muscle.
Insertion
- The mobile, distal attachment of a muscle.
Belly
- The thick, fleshy part of the muscle.

Functions of Muscles

Movement
Heat Generation
- Muscle contraction produces heat as a byproduct.
Shape and Contour

Extrinsic and Intrinsic Muscles of the Eye

Extrinsic Muscles
- Located outside the eyeball; enables voluntary movement. Examples: superior rectus, inferior oblique.
Intrinsic Muscles
- Situated within the eyeball; involuntary muscles. Include ciliary muscle, sphincter pupillae, and dilator pupillae.

Muscles of the Neck

Suprahyoid Muscles: Located above the hyoid bone, important for swallowing and speech.
Infrahyoid Muscles: Located below the hyoid bone, assist in stabilizing the hyoid and help in swallowing.

Superficial Muscles of the Neck

Deep Investing Fascia: Wraps around the neck, separates muscles, and attaches to various structures, including the mandible and clavicles.
Visceral/Pretracheal Fascia: Forms a sheath around neck viscera, attaches to the hyoid bone and the pericardium of the heart.
Prevertebral Fascia: Encloses cervical vertebral unit, attaching to the base of the skull and the thoracic longitudinal ligament.
Alar Fascia: Division of prevertebral fascia that binds to the transverse processes of cervical vertebrae.

Muscles of the Thorax

Diaphragm: Main muscle of inspiration, contracts to increase thoracic volume; supplied by the phrenic nerve (C3-5).
- Right Crus: Arises from lumbar vertebrae.
- Left Crus: Arises from the bodies of the first two lumbar vertebrae.
External Intercostal Muscles: Fibers run downward and forward, raising ribs during inspiration, lowering them with abdominal muscles during expiration.

Types of Muscles

Skeletal Striated Muscle: Voluntary muscle that forms skeletal structure.
Cardiac Striated Muscle: Involuntary, forms heart wall.
Smooth Unstriated Muscle: Involuntary, present in vessels and hollow organs.

Muscle Attachments

Tendon: Connects muscle to bone.
Origin: Fixed attachment point.
Insertion: Movable end during contraction.
Belly: Fleshy middle portion of the muscle.

Fascia and Fascicle Arrangement

Fascia: Connective tissue surrounding muscles and structures, facilitating movement.
Arrangements: Include fusiform, circular, triangular, parallel, and pennate.

Coordination Among Muscles

Agonist (Prime Mover): Muscle causing the desired movement.
Antagonist: Muscle that relaxes during the movement.
Synergist: Assists agonist in movement execution.
Fixator: Stabilizes the origin of the agonist for effective movement.

Clinical Relevance

Understanding muscle anatomy is crucial for evaluating neck and thoracic conditions and interventions.

Objectives

Layers of the scalp include five distinct layers: skin, connective tissue, aponeurosis, loose areolar tissue, and pericranium.
Understanding each layer's features is essential for grasping scalp anatomy.
The 4th layer, loose areolar tissue, is termed the "dangerous layer" due to its potential for rapid infection spread and bleeding.

Scalp Layers

Skin: Contains hair follicles and sebaceous glands.
Connective Tissue: Rich in blood vessels and nerves, responsible for scalp tension.
Aponeurosis: Tendinous sheet of occipitofrontalis muscle connects the front and back portions of the scalp.
Loose Areolar Tissue: Allows mobility of the scalp; infection can spread easily.
Pericranium: Periosteum of skull bones, dense connective tissue layer.

Characteristics of Scalp Wounds

Clean wounds in the scalp heal promptly due to rich vascular supply.
Incised wounds along the coronal plane gape due to tension in connective tissue.
Wounds involving the first two layers bleed profusely due to numerous blood vessels.
Bleeding in the 4th layer is diffuse; it can spread to the face via gravity.
Bleeding under the 5th layer remains localized, affecting specific cranial bones.

Occipitofrontalis Muscle

Occipital Belly: Originates from the highest nuchal line of the occipital bone, inserts into epicranial aponeurosis, moves the scalp on skull.
Frontal Belly: Originates from skin and fascia of eyebrows, inserts into the same aponeurosis, raises the eyebrows.
Innervated by the facial nerve.

Muscles of Facial Expression

Orbicularis Oculi: Originates from the lacrimal bone, closes eyelids, innervated by the facial nerve.
Dilator Naris: Originates from maxilla, widens nasal aperture, innervated by facial nerve.
Procerus: Originates from nasal bone, wrinkles skin between eyebrows, innervated by facial nerve.

Edema and Swelling in the Face

Rapid swelling occurs in the dangerous area due to a lack of deep fascia.
The area between the eyes and upper lip, or eyes and sides of the nose is pivotal for infection spread.

Dangerous Area of the Face

Drained by the facial vein, increasing risk of infection spread to the cavernous sinus, which can result in cerebral edema.

Blood Supply of the Face

Facial Artery: Main artery supplying the face from the external carotid artery (ECA).
Superficial Temporal Artery: Supplies scalp, branches from ECA.
Supraorbital & Supratrochlear Arteries: Supply forehead, branches of the ophthalmic artery.

Muscles of Mastication

Lateral Pterygoid:
- Superior head: Originates from infratemporal surface, inserts at the neck of the mandible.
- Inferior head: Lateral surface of lateral pterygoid plate; enables side-to-side movement and protrusion of the mandible.
- Innervated by the mandibular nerve via the temporomandibular joint nerve.

Mandible Study Focus

Morphology includes body shape and angle.
Articulating parts are crucial for jaw movement.
Understanding dislocation mechanics is vital for clinical assessment.

Generalities of Muscles

Cardiac muscle is found exclusively in the heart, featuring striated cells with intercalated discs and typically one nucleus.
It contracts involuntarily and rhythmically, pumping blood, influenced by the autonomic nervous system.
Skeletal muscle, known as striated muscle, is under voluntary control and is responsible for body movement.

Types of Muscle Tissue

Cardiac Muscle:
- Strong, quick, continuous contractions.
- Major role is to maintain heart function.
Skeletal Muscle:
- Attached to the skeleton, enables voluntary movement.
- Comprises named muscles, such as biceps brachii.
Smooth Muscle:
- Involuntary contractions, controls bodily functions like peristalsis and blood vessel diameter.

Muscle Innervation

Branchiomeric muscles of the second branchial arch innervated by the facial nerve; includes muscles of facial expression.
The stylopharyngeus (third arch) is innervated by the glossopharyngeal nerve.
Fourth and sixth arch muscles innervated by the vagus nerve, a mixed nerve contributing to motor and sensory functions.

Muscle Action Potential

Key phases include:
- Depolarization
- Overshoot
- Repolarization
- Hypopolarization
- Hyperpolarization

Disuse Atrophy

Caused by inadequate muscle use; leads to rapid muscle degeneration and loss of functional capacity.
Fiber weakness and size reduction can occur within hours of denervation, as the body reallocates energy.

Muscle Nomenclature Bases

Action: Muscles are named based on their movements (e.g., dilator nares).
Location: Naming can reflect the position relative to bones (e.g., pectoralis major/minor, biceps brachii).
Depth distinctions: Superficialis (superficial) vs. profundus (deep).

Intrinsic vs. Extrinsic Muscles

Intrinsic muscles act entirely within the body part (e.g., hand, foot).
Extrinsic muscles originate outside the acting body part but attach in or on it (e.g., forearm muscles affecting hand movement).

Muscle Abnormalities and Diseases

Chorea: Sudden, jerky, involuntary movements due to dopamine overactivity; associated with several disorders.
Hemiballismus: Characterized by violent, involuntary movements of limbs due to central nervous system dysfunction.
Myelitis: Inflammation of the spinal cord which damages myelin, affecting nerve signal transmission.

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Description

Test your understanding of different muscle types and their innervation in the human body. This quiz covers cardiac, skeletal, and smooth muscles, as well as branchial musculature and cranial nerves. Explore the unique features and functions that distinguish each muscle type.