TBL 11 Flashcards
What is the layer of the skin the hair follicles and sweat glands anchored in?
superficial fascia
dermoepidermal junction
single layer of basal cells, proliferate to generate cuboidal cells that move to the apical sufrace (become keratinized)
Stratum corneum
layers of anucleate keratinocytes completely filled with keratin; layer at free surface is continously shed
Thick skin vs thin skin
thin skin = sweat glands, hair follicles; thick skin = sweat glands, no hair follicles
Desmosomes
aggregates of cellular adhesion proteins in cell membranes of adjacent keratinocytes that interconnect the cells and resist their mechanical abrasion
Hemi-desmosomes
links the basal layer of the epidermis and the basement membrane
Is basal cell carcinoma or squamous cell carcinoma more likely to breech the basement membrane? Which tumor is more prevalent?
Basal cell carcinoma accounts for 90% of cancers, rarely breaches; Sq. cell is associated with sun and has a greater likelihood of metastasis
Melanosomes. What determines skin color?
produce melanin in melanosomes which are deposited into cytoplasm of keratinocytes; rate of melanosome production determines skin color
Langerhans cells
2-8% of epidermal population; DCs are capture invading antigens to assist selective activation of T cells
How do hair buds form?
Basal cells penetrate dermis, terminal ends become hair papillae -> includes keratinocytes, melanocytes -> hair shafts
Sebaceous glands
from the follicular wall of hair bud, basal cells form sebaceous glands -> secrete sebum (lipid-rich decomposed granular cells)
Arrector pili
sympathetic-mediated, contraction causes goosebumps and compresses the sebaceous glands to expedites sebum secretion into the follicle
How sweat glands form?
invaginations of epidermal basal cells (similar to hair bud formation) down into the superficial fascia; postsynaptic sympathetic fibers activat the secretory acini
How do eccrine sweat glands help maintain body temperature?
sweat, evaporative heat loss
Where do odoriferous sweat glands reside, and why do their secretions have a musky odor?
axillae, scrotum, prepuce, labia minora, nipples, and perinatal regions; musky odor is in response to bacterial decomposition
Superficial fascia and function
white fat (adipocytes with large lipid droplets filling their cytoplasm) -> insulation, padding for underlying tissues, metabolic fuel
Meissner’s corpuscle
in the superficial dermis, mechanoreceptor -> sensitive to fine tactile stimuli
Pacinian corpuscle
in the superficial fascia, mechanoreceptor -> sensitive to pressure, vibration, and gross tactile stimuli
Axial skeleton
Skull, vertebral column, ribs, sternum
Intervertebral (IV) discs, accounts for height of prescaral vertebral column?
25%
of presacral vertebrae
24
structure of presacral vertebrae
anterior vertebral body, posterior vertebral arches, vertebral foramina
vertebral foramina ( continuity = vertebral canal)
encloses the spinal cord, spinal nerve roots, DRG
Pedicle vs laminae of the vertebral arch
Pedicle = sides; Laminae = roof
Ligmenta flava
interconnect the laminae of adjacent vertebrae and contribute to the posterior wall of the vertebral canal
Medial vs lateral
lateral farther from the median plane
Junction of pedicles and laminae
transverse processes and two superior and two inferior articular processes
Junction of laminae
single spinous process
Function of transverse and spinous processes
provide attachment sites for deep back muscles that fix or change positions of the vertebrae
Alignment of articular processes
lie in apposition above and below the vertebrae (the condition of being side by side or close together)
Spondylolysis
fracture of a vertebral arch between its superior and inferior articular processes (i.e at the pars interarticularis -> junction between laminae and pedicle)
What are the consequences of spondylolysis at L5?
Spondylolisthesis -> may result in pressure on the spinal nerves of the cauda equina, causing lower back and lower limb pain
How do the ligamenta flava expedite a lumbar spinal puncture?
There is release of pressure when puncturing
IV discs structure
gelatinous nucleus pulposus surrounded by annulus fibrosis (concentric layers of thick collagen fibers); shock absorbers for the spine
Primary curvatures
Thoracic, Sacral
Secondary curvatures
Cervical, Lumbar; begin to form when infants can lift their heads and start to walk, respectively
Where do spinal nerves pass through in the foramina?
superior portions
How are cervical spinal nerves numbered?
Nerves passes superior to the corresponding vertebrae
How are thoracic and lumbar spinal nerves numbered?
Nerves passes through IV foramina inferior to the corresponding vertebrase
Disc herniation between vertebrae L4 and L5 compresses which spinal nerve root?
L5 nerve
Disc herniation between vertebrae C4 and C5 compresses which spinal nerve root?
C5 nerve
Notochord
induces formation of the axial skeleton, neural tube, and nucleus pulposus
Annulus fibrosis originate from what tissue/structure?
somite-derived mesenchymal cells
What causes spina bifida occulta, the most common congenital anomaly of the vertebral column?
neural arches of L5 and/or S1 fail to develop normally and fuse posterior to the bertebral canal
How does spina bifida cystica differ from spina bifida occulta?
cystica is more severe, herniation of the meninges and/or the spinal cord
Development of skeletal muscle fibers
Mesenchymal cells -> myoblasts -> end to end fusion -> myotube -> cell fusion -> myofilaments -> muscle fibers (actin and myosin appear)
Organization of skeletal muscle
Sacromere -> myofilament -> myofibril -> muscle fiber -> muscle fasicles -> muscle
A bands
myosin
I bands
actin
Z lines
decmarcate sacromeres
Epimysium
dense connective tissue surrounding the entire muscle
Perimysium
dense connective tissue surrounding the fascicles
Endomysium
dense connective tissue surrounding the muscle fibers
T tubules
tubular invagination of the sarcolemma form triads with portions of the sacroplasma reticulum that enable rapid conduction of the electrical impulses to the cell interior for excitation-contraction coupling
Muscle action potential
Ach released from the axon terminal binds to the muscle fiber sarcolemma
Tendons arise directly from the epimysium
the sarcolemma beneath the epimysium is highly indented to enhance mechanical stability of the muscle-tendon junction
What is the function of satellite cells?
stem cells, for repair and regeneration of damaged segments of the skeletal muscle fiber after injury
What is the role of muscle tone and when is it absent?
gives muscle a certain firmness, assisting the stability of joints and the maintance of posture, while keeping the muscle ready to respond to appropriate stimuli. Absent when unconscious or after a nerve lesion resulting in paralysis
What form the arrector pili and smooth muscle of arteries?
local mesenchymal cells
Smooth muscle characteristics
lack striations; actin filaments align parallel with myosin filaments and bind to dense bodies dispersed within the sarcoplasm
Varicosities along postsynaptic sympathetic fibers
release norepinephrine that binds to the smooth muscle fiber sarcolemma; tiny intercellular pores (aka gap junctions) enable action potentials to spread among groups of smooth muscle fibers for synchronous contraction.
Superficial extrinsic shoulder muscles
trapezius and latissimus dorsi
Deep extrinsic shoulder muscles
levator scapulae and rhomboids
Trapezius
attaches to the cervical and thoracic vertebrae proximally and to the scapula and clavicle distally; its superior part elevates the scapula, and all three of its parts working together retract the scapula from the protracted position (i.e., pulling something toward you after reaching for it).
Latissimus dorsi
attaches via the thoracolumbar fascia to the inferior six thoracic and five lumbar vertebrae proximally and its tendon attaches to the medial side of the humerus distally; it rotates the scapula downward and adducts the upper extremity from the fully abducted position (e.g., swimming or climbing).
Innervates the trapezius
spinal accessory nerve
Innvervates the latissimus dorsi
thoracodorsal nerve
What is the clinical manifestation in patients with ipsilateral trapezius muscle weakness?
spinal accessory nerve palsy; weaknes when shoulders are elevated against resistance
Why is the use of crutches difficult by an adult with latissimus dorsi weakness, and how would the weakness affect a 1-year old infant?
crutches pushes shoulder superiorly; a 1 year old would not be able to crawl
Levator scapulae
attaches to the superior four cervical vertebrae proximally and to the superior angle of the scapula distally; synergizes with the superior part of the trapezius during elevation of the scapula.
Rhomboids
attach to the superior six thoracic vertebrae proximally and to the medial border of the scapula distally; assist retraction and downward rotation of the scapula.
Dorsal scapular nerve
C5 is the spinal segmental origin; innervates the levator scapulae and rhomboids
Erector spinae
considered the long intrinsic muscle of the back; thus, it attaches to the sacrum proximally and to the posterior aspects of the ribs, thoracic vertebrae, and cervical vertebrae distally.
Erector spinae innervation
posterior rami of the spinal nerves innervate the erector spinae and envision the rami also conduct somatic sensations from the back into the CNS.
Erector spinae function
after flexion of the vertebral column by the rectus abdominis muscle of the anterior abdominal wall (to be studied later), bilateral contraction of the erector spinae extends the spine to return it to the upright position.
