Hair Follicle Anatomy
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Questions and Answers

What is the primary function of the periderm layer during embryonic development?

  • To provide a protective barrier against amniotic fluid (correct)
  • To allow for the proliferation of basal cells
  • To facilitate the differentiation of spinous cells
  • To induce the formation of hair placodes

    • What is the role of Notch signaling in the differentiation of spinous cells?

  • Notch signaling directs spinous cells to continue differentiating and migrate towards the surface of the skin (correct)
  • Notch signaling is responsible for the formation of hair placodes
  • Notch signaling is required for the proliferation of basal cells
  • Notch signaling induces the expression of K1 in spinous cells

    • Which of the following cell types is NOT found in the intermediate layer of the embryonic skin?

  • Undifferentiated cells
  • Proliferating basal cells
  • Cornified cells (correct)
  • Spinous cells

    • Which of the following is a unique property of the basal layer of the epidermis?

    <p>The basal layer is composed of multipotent epithelial cells</p> Signup and view all the answers

    What is the primary function of the hair placodes that form in the underlying dermis?

    <p>To give rise to hair follicles</p> Signup and view all the answers

    Which of the following cell types is responsible for the formation of the granular layer and cornified layer of the epidermis?

    <p>Spinous cells</p> Signup and view all the answers

    Which layer of the hair follicle is heavily keratinized and has a fish-scale appearance?

    <p>Cuticle</p> Signup and view all the answers

    Which layer of the hair follicle is pigmented and non-keratinized?

    <p>Medulla</p> Signup and view all the answers

    Which cells in the hair follicle produce the cortex of the hair shaft?

    <p>Lateral cells (B)</p> Signup and view all the answers

    During which phase of the hair growth cycle does the hair shaft exit the follicle?

    <p>Exogen</p> Signup and view all the answers

    Which structure in the hair follicle contains capillaries and is covered by cells that form the hair root and develop into the hair shaft?

    <p>Dermal papilla</p> Signup and view all the answers

    During which phase of the hair growth cycle does cell division cease in the bulb, the papilla shrinks, and the shaft and inner root sheath detach from the dermal papilla?

    <p>Catagen</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between the external root sheath and the epidermis?

    <p>The external root sheath is continuous with the epidermis.</p> Signup and view all the answers

    At what level do the cells of the internal root sheath disappear?

    <p>At the level of the sebaceous gland ducts</p> Signup and view all the answers

    Which of the following statements accurately describes the origin and insertion of the arrector pili muscle?

    <p>It originates in the connective tissue sheath of the hair follicle and inserts into the papillary layer of the dermis.</p> Signup and view all the answers

    Which of the following statements accurately describes the development of the epidermis?

    <p>The multipotent epithelial cells in the surface ectoderm become the embryonic epidermal basal layer.</p> Signup and view all the answers

    Which of the following statements accurately describes the function of the basement membrane in the development of the epidermis?

    <p>The basement membrane separates the epidermis from the dermis and provides epidermal basal cells with growth factors.</p> Signup and view all the answers

    Which of the following statements accurately describes the attachment of basal cells to the basement membrane?

    <p>Basal cells attach to the basement membrane through focal adhesions and hemidesmosomes composed of integrins.</p> Signup and view all the answers

    What marks the transition from stage 4 to stage 5 of hair follicle development?

    <p>Formation of inner root sheath</p> Signup and view all the answers

    Which stage is characterized by the formation of a spherical dermal papilla adjacent to the hair peg?

    <p>Stage 3</p> Signup and view all the answers

    At which stage does the hair shaft begin to form at the upper end of the hair follicle?

    <p>Stage 6</p> Signup and view all the answers

    During which stage does the dermal papilla become fully enclosed?

    <p>Stage 8</p> Signup and view all the answers

    What happens to the hair shaft in stage 7 of hair follicle development?

    <p>It leaves the inner root sheath</p> Signup and view all the answers

    Which stage involves the elongation of the inner root sheath up the hair follicle?

    <p>Stage 5</p> Signup and view all the answers

    Which layer of the epidermis is responsible for the production of melanin?

    <p>Stratum basale</p> Signup and view all the answers

    What is the primary function of the stratum lucidum layer?

    <p>Protection from UV radiation</p> Signup and view all the answers

    Which layer of the epidermis contains Langerhans' cells, which play a role in the immune response?

    <p>Stratum spinosum</p> Signup and view all the answers

    What is the characteristic appearance of cells in the stratum spinosum layer under a light microscope?

    <p>Spiny projections</p> Signup and view all the answers

    Which layer of the epidermis contains the stem cells responsible for cell division and renewal?

    <p>Stratum basale</p> Signup and view all the answers

    Which division of the brachial plexus trunks is responsible for innervating the muscles of the anterior compartment of the arm and forearm?

    <p>Anterior divisions</p> Signup and view all the answers

    What is the primary function of Merkel cells in the epidermis?

    <p>Mechanoreception</p> Signup and view all the answers

    Which of the following structures does the brachial plexus NOT form?

    <p>Femoral nerve</p> Signup and view all the answers

    Which part of the brachial plexus is responsible for providing sympathetic innervation?

    <p>The roots</p> Signup and view all the answers

    Which cord of the brachial plexus is formed by the union of the anterior divisions of the superior and middle trunks?

    <p>Lateral cord</p> Signup and view all the answers

    Which muscle(s) are innervated by the posterior divisions of the brachial plexus trunks?

    <p>Muscles of the posterior compartment of the arm and forearm</p> Signup and view all the answers

    Which of the following disorders is NOT typically associated with damage to the brachial plexus?

    <p>Amyotrophic lateral sclerosis</p> Signup and view all the answers

    Which nerve innervates the pectoralis major but also sends a loop to the medial pectoral nerve that innervates the pectoralis minor?

    <p>Lateral pectoral nerve</p> Signup and view all the answers

    Which branch of the posterior cord receives fibers from C5 and C6 and innervates the superior portion of the subscapularis muscle?

    <p>Upper subscapular nerve</p> Signup and view all the answers

    Which terminal branch of the posterior cord innervates the teres minor and deltoid muscles, as well as the glenohumeral joint and skin over the inferior part of the deltoid?

    <p>Axillary nerve</p> Signup and view all the answers

    Which nerve emerges from both the medial and lateral cords and supplies all flexors of the forearm except for the flexor carpi ulnaris and the medial half of the flexor digitorum profundus?

    <p>Median nerve</p> Signup and view all the answers

    Which branch of the brachial plexus can lead to an 'Ape Hand' deformity when injured?

    <p>Median nerve</p> Signup and view all the answers

    The hand of benediction deformity is associated with damage to which nerve?

    <p>Median nerve</p> Signup and view all the answers

    Which nerve supplies most of the intrinsic muscles of the hand including the hypothenar eminence, and skin on the medial side of the hand?

    <p>Ulnar nerve</p> Signup and view all the answers

    Injury to which nerve results in 'wrist drop'?

    <p>Radial nerve</p> Signup and view all the answers

    Which nerve supplies the biceps, coracobrachialis, and brachialis muscles?

    <p>Musculocutaneous nerve</p> Signup and view all the answers

    Ape Hand deformity is associated with the compression of which nerve?

    <p>Median nerve</p> Signup and view all the answers

    Waiter's tip deformity is characteristic of injury to which part of the brachial plexus?

    <p>Upper trunk</p> Signup and view all the answers

    'Claw Hand' deformity is a result of injury to which nerve?

    <p>Ulnar nerve</p> Signup and view all the answers

    Which of the following muscles are innervated by the lateral cord of the brachial plexus?

    <p>Flexor carpi radialis, Flexor digitorum profundus</p> Signup and view all the answers

    Which nerve root compression is associated with the condition known as 'Klumpke's palsy'?

    <p>C7-T1</p> Signup and view all the answers

    Which of the following muscles is innervated by the posterior cord of the brachial plexus?

    <p>Teres major</p> Signup and view all the answers

    Which of the following conditions is NOT typically associated with brachial plexus injury?

    <p>Carpal tunnel syndrome</p> Signup and view all the answers

    Which nerve root compression is associated with the condition known as 'Erb's palsy'?

    <p>C5-C6</p> Signup and view all the answers

    Which of the following muscles is innervated by the medial cord of the brachial plexus?

    <p>Pronator teres</p> Signup and view all the answers

    Which of the following muscles is innervated by the dorsal scapular nerve?

    <p>Rhomboids</p> Signup and view all the answers

    A patient presents with winging of the scapula, which is indicative of a lesion involving which nerve?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which of the following muscles is innervated by the nerve to subclavius?

    <p>Subclavius</p> Signup and view all the answers

    A patient complains of dull, aching pain in the posterior shoulder region, which may indicate a lesion involving which nerve?

    <p>Suprascapular nerve</p> Signup and view all the answers

    Which of the following muscles is responsible for abduction of the arm at the shoulder joint?

    <p>Supraspinatus</p> Signup and view all the answers

    A lesion involving which nerve may lead to difficulty in protraction of the scapula during arm elevation?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which nerve is responsible for innervating the majority of the intrinsic muscles of the hand, including the thenar eminence, as well as the skin on the medial side of the hand?

    <p>Median nerve</p> Signup and view all the answers

    Which nerve branch of the brachial plexus is responsible for innervating the pectoralis major muscle, but also sends a communicating loop to the medial pectoral nerve that supplies the pectoralis minor muscle?

    <p>Lateral pectoral nerve</p> Signup and view all the answers

    Which of the following conditions is characterized by the 'ape hand' deformity, resulting from damage to a specific nerve?

    <p>Median nerve injury</p> Signup and view all the answers

    Which nerve branch of the brachial plexus is responsible for innervating the triceps brachii, anconeus, brachioradialis, and extensor muscles of the forearm, as well as providing cutaneous innervation to the posterior aspect of the arm and forearm?

    <p>Radial nerve</p> Signup and view all the answers

    Injury to which nerve of the brachial plexus is associated with the characteristic 'winging of the scapula' deformity?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which nerve of the brachial plexus is responsible for providing sympathetic innervation?

    <p>Rami communicantes</p> Signup and view all the answers

    Which nerve supplies most of the intrinsic muscles of the hand including the hypothenar eminence, and skin on the medial side of the hand?

    <p>Ulnar nerve</p> Signup and view all the answers

    Which nerve supplies the deltoid and teres minor muscles?

    <p>Axillary nerve</p> Signup and view all the answers

    Injury to which nerve results in 'wrist drop'?

    <p>Radial nerve</p> Signup and view all the answers

    Which brachial plexus injury results in 'Waiter’s tip deformity'?

    <p>Suprascapular nerve injury</p> Signup and view all the answers

    Which nerve supplies the biceps, coracobrachialis, and brachialis muscles?

    <p>Musculocutaneous nerve</p> Signup and view all the answers

    'Ape Hand' deformity is associated with injury to which nerve?

    <p>Radial nerve</p> Signup and view all the answers

    Which of the following muscles is innervated by the axillary nerve, a terminal branch of the posterior cord?

    <p>Deltoid</p> Signup and view all the answers

    Injury to which nerve can result in the 'waiter's tip' deformity, characterized by the inability to extend the wrist and fingers?

    <p>Radial nerve</p> Signup and view all the answers

    Which of the following muscles is supplied by the thoracodorsal nerve, a branch of the posterior cord?

    <p>Latissimus dorsi</p> Signup and view all the answers

    Which condition is associated with the compression of the C8 and T1 nerve roots, resulting in paralysis of the intrinsic muscles of the hand?

    <p>Klumpke's palsy</p> Signup and view all the answers

    Which of the following muscles is innervated by the medial pectoral nerve, a branch of the medial cord?

    <p>Pectoralis minor</p> Signup and view all the answers

    Injury to which nerve can result in the 'ape hand' deformity, characterized by the inability to abduct and oppose the thumb?

    <p>Median nerve</p> Signup and view all the answers

    Which nerve is responsible for innervating the three thenar muscles, leading to atrophy known as 'ape hand' when damaged?

    <p>Median nerve</p> Signup and view all the answers

    Which nerve emerges from both the medial and lateral cords of the brachial plexus and supplies all flexors of the forearm except for the flexor carpi ulnaris and the medial half of the flexor digitorum profundus?

    <p>Median nerve</p> Signup and view all the answers

    Which brachial plexus nerve branch can result in an 'Ape Hand' deformity when injured?

    <p>Median nerve</p> Signup and view all the answers

    Which part of the brachial plexus is responsible for providing sympathetic innervation?

    <p>Lateral cord</p> Signup and view all the answers

    Which nerve root compression is associated with 'Erb's palsy,' a condition that affects the shoulder and arm muscles?

    <p>C5-C6</p> Signup and view all the answers

    Which of the following conditions is NOT typically associated with brachial plexus injury?

    <p>Ape Hand deformity</p> Signup and view all the answers

    Which of the following nerves innervates the rhomboid muscles?

    <p>Dorsal scapular nerve</p> Signup and view all the answers

    Injury to which nerve can lead to the 'winged scapula' deformity?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which nerve innervates the supraspinatus and infraspinatus muscles, as well as the glenohumeral (shoulder) joint?

    <p>Suprascapular nerve</p> Signup and view all the answers

    Which nerve innervates the subclavius muscle and the sternoclavicular joint?

    <p>Nerve to subclavius</p> Signup and view all the answers

    Injury to which nerve can cause an 'Ape Hand' deformity?

    <p>Ulnar nerve</p> Signup and view all the answers

    Which of the following nerves innervates the serratus anterior muscle?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which nerve branch of the brachial plexus is responsible for innervating the superior portion of the subscapularis muscle?

    <p>Upper subscapular nerve</p> Signup and view all the answers

    Which of the following statements about the upper subscapular nerve is correct?

    <p>It receives fibers from the C5 and C6 nerve roots.</p> Signup and view all the answers

    Injury to which nerve branch of the brachial plexus can result in winging of the scapula?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which muscle is primarily innervated by the upper subscapular nerve?

    <p>Subscapularis</p> Signup and view all the answers

    Where does the upper subscapular nerve originate from within the brachial plexus?

    <p>Posterior cord</p> Signup and view all the answers

    Which of the following statements about the upper subscapular nerve is false?

    <p>It innervates the teres minor muscle.</p> Signup and view all the answers

    Which nerve is responsible for innervating the supraspinatus, infraspinatus, and glenohumeral (shoulder) joint?

    <p>Suprascapular nerve</p> Signup and view all the answers

    What is the course of the suprascapular nerve?

    <p>Passes laterally across the posterior triangle of the neck, through the scapular notch under the superior transverse scapular ligament</p> Signup and view all the answers

    Which nerve arises from the anterior rami of C5-C7 and innervates the serratus anterior muscle?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which nerve arises from the superior trunk receiving fibers from C5, C6, and often C4, and innervates the subclavius muscle and sternoclavicular joint?

    <p>Nerve to subclavius</p> Signup and view all the answers

    Which nerve arises from the anterior ramus of C5 with a frequent contribution from C4, pierces the middle scalene, descends deep to the levator scapulae, and innervates the rhomboid muscles?

    <p>Dorsal scapular nerve</p> Signup and view all the answers

    Which nerve is responsible for innervating the supraspinatus muscle and the glenohumeral (shoulder) joint, but not the infraspinatus muscle?

    <p>Suprascapular nerve</p> Signup and view all the answers

    Which nerve supplies the superior portion of the subscapularis muscle?

    <p>Upper subscapular nerve</p> Signup and view all the answers

    Which nerve passes posteriorly and enters the subscapularis muscle?

    <p>Lower subscapular nerve</p> Signup and view all the answers

    Which nerve innervates the inferior portion of the subscapularis muscle and the teres major muscle?

    <p>Lower subscapular nerve</p> Signup and view all the answers

    Which nerve supplies the teres minor and deltoid muscles?

    <p>Axillary nerve</p> Signup and view all the answers

    Which nerve receives fibers from C5 and C6 and runs inferolaterally to innervate latissimus dorsi?

    <p>Thoracodorsal nerve</p> Signup and view all the answers

    Which nerve descends posteriorly to innervate triceps brachii and anconeus?

    <p>Radial nerve</p> Signup and view all the answers

    Which nerve originates from both the medial and lateral cords and supplies all flexors of the forearm except for flexor carpi ulnaris?

    <p>Median nerve</p> Signup and view all the answers

    'Hand of Benediction' deformity is associated with damage to which nerve?

    <p>Median nerve</p> Signup and view all the answers

    Study Notes

    Embryonic Skin Development

    • The periderm layer serves as a protective covering during early embryonic development.
    • Notch signaling is pivotal in the differentiation of spinous cells, influencing their maturation.
    • The intermediate layer of embryonic skin does not contain keratinocytes; it consists mainly of peridermal and spinous cells.
    • Unique to the basal layer of the epidermis is its ability to continuously divide and renew itself.
    • Hair placodes in the dermis are essential for initiating hair follicle formation and guiding hair development.
    • Keratinocytes are responsible for forming the granular layer and cornified layer of the epidermis.
    • The outer root sheath of the hair follicle features a heavily keratinized, fish-scale appearance.
    • The inner root sheath is pigmented and non-keratinized, adding to the hair's structural integrity.
    • The cortex of the hair shaft is formed by keratinocytes within the hair follicle.
    • During the anagen phase, the hair shaft emerges from the follicle.
    • The hair bulb contains capillaries and cells that develop into the hair shaft.
    • Catagen phase involves reduced cell division within the bulb, leading to detachment from the dermal papilla.
    • The external root sheath is derived from the epidermis, reflecting a close developmental relationship.
    • Internal root sheath cells vanish at the upper part of the hair follicle.
    • The arrector pili muscle originates from the dermal layer and inserts into the hair follicle, enabling hair to stand when cold or scared.
    • Epidermis development involves a complex interaction of signaling pathways and cellular differentiation.
    • The basement membrane plays a crucial role in epidermis structural support and cellular attachment.
    • Basal cells anchor to the basement membrane through hemidesmosomes, maintaining epidermal integrity.
    • Transition from stage 4 to 5 of hair follicle development is marked by interactions between the hair strand and dermal papilla.
    • Stage 3 features the formation of a spherical dermal papilla near the hair peg.
    • The hair shaft begins formation in stage 4 of hair follicle development.
    • The dermal papilla becomes fully enclosed during stage 6.
    • In stage 7, the hair shaft undergoes keratinization before forming a complete hair strand.
    • The inner root sheath elongates upwards the follicle during its development stages.
    • Melanocytes within the stratum basale are responsible for melanin production.
    • The stratum lucidum layer primarily acts as a barrier to protect deeper skin layers.
    • The stratum spinosum features Langerhans cells, integral to the immune response in the skin.
    • Cells in the stratum spinosum appear spiky or "prickly" under a light microscope due to desmosomal connections.
    • The basal layer of the epidermis is where stem cells for ongoing cell renewal reside.
    • The lateral cord of the brachial plexus innervates muscles in the anterior arm and forearm.
    • Merkel cells in the epidermis function as mechanoreceptors, detecting touch and pressure.
    • The brachial plexus does not form the cranial nerves; it pertains to peripheral innervations.
    • Sympathetic innervation arises from the sympathetic trunk and is linked to the brachial plexus.
    • The posterior cord is formed by the combined anterior divisions of the brachial plexus trunks.
    • Posterior divisions innervate muscles like the deltoid and teres minor.
    • Conditions such as 'Ape Hand' result from median nerve injuries affecting thumb function.
    • The hand of benediction deformity signifies ulnar nerve injury affecting finger extension.
    • The ulnar nerve supplies the majority of hand's intrinsic muscles, influencing movements and sensation.
    • Wrist drop is a symptom of radial nerve injury affecting wrist extension.
    • The musculocutaneous nerve innervates biceps, coracobrachialis, and brachialis muscles.
    • Injury to the median nerve is associated with 'Ape Hand' due to the paralysis of the thenar muscles.
    • The waiter's tip deformity is linked to upper brachial plexus injury affecting deltoid muscle activation.
    • The intrinsic muscles' paralysis from lower trunk compression leads to Klumpke's palsy, impacting hand function.
    • The thoracodorsal nerve innervates the latissimus dorsi muscle.
    • The long thoracic nerve innervates the serratus anterior, and its injury can lead to scapula winging.
    • The upper subscapular nerve arises from the posterior cord and innervates the subscapularis muscle.
    • Suprascapular nerve innervates both supraspinatus and infraspinatus muscles, critical for shoulder stability.
    • A lesion affecting the dorsal scapular nerve can lead to scapula winging, impacting upper limb movement.
    • The medial pectoral nerve is responsible for innervating pectoralis major and minor, contributing to shoulder function.

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    Description

    Test your knowledge on the anatomy of the hair follicle including the external and internal root sheath, hair shaft, glassy membrane, and more. Understand the relationships between the skin layers, arrector pili muscle, sebaceous, and sweat glands.

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