CA1 Skin/Nervous System
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What are the 3 layers of the skin?
- Subcutaneous (hypodermis)
What does epi mean?
Upon (thus the top layer of the skin)
Which layer is superficial/deep?
- Epidermis is the most superficial layer, it is the protective coating, made up of stratified squamous (keratinized) cells
- Dermis is the deep inner layer made up of fibrous connective tissue, epithelial tissue, smooth muscle, nervous tissue, blood vessels, and basement membrane
- Subcutaneous (hypodermis = beneath the dermis) is the deepest layer made up of loose connective tissue, adipose (fat insulation), and binds skin to the underlying organs (muscle)
Do stratified squamous epithelial cells of the epidermis lack direct blood supply?
YES, nutrients get to this level through diffusion from the underlying dermis layer
- Base or bottom - deepest layer of epidermis cells
- Have the ability to divide & grow (replace)
- As new cells develop they push older cells away from the dermis (toward the surface), the further away they get the older the cells are, the less nutrients they receive and eventually they die
- Cell membranes on the older cells develop desmonsomes (spot welds holding things together) (keep water out)
- Cells also begin to keratinize (hardening with strands of tough fibrous water proof keratin protein)
Stratum corneum (hard/dead)
- Top most layer of epidermis composed of layers of dead keratinized tightly packed cells
- Slough off with rubbing (dry skin)
What are the layers of the Epidermis?
- Stratum basale (deepest)
- Stratum spinsum (relativly thick layer)
- Stratum granulosum (granualr layer)
- Stratum lucidium (found in thickened skin of palms and soles)
- Stratum corneum (most superficial layer, fully keratinized cells)
What makes skin "healthy skin"?
The production (at the basale) of epidermal cells is balanced with the loss of dead cells from the stratum corneum so that our skin does not wear away.
When the skin is rubbed or pressed regularly is the rate of cell division increased or decreased?
Increased (think caluses on the soles of the feet)
What is psoriasis?
- When cells in the epidermis divide 7 times faster than normal
- Excess cell accumulate & form bright red patches with silvery scales (keratinized cells).
What is the typical thickness of skin on the palms and soles?
- .8-1.4mm only have stratum lucidum
- The average on the rest of the body is (.07-.12mm) and may not have stratum lucidum
What produces pigment (color) in the skin?
- Melanocytes or melanin
- Absorbs light energy
- Protects deeper layer of growing cells from UV light (sunlight)
- Found in deepest (basale) portion of epidermis and dermis
What is sun exposure & how does it effect the skin?
- Continued sun expospure leads to tanning/burning
- Specialized skin cells (melanocytes) produce more melanin pigment
- Stratum corneum begins to thicken
- Skin may feel leathery and loose elasticity
"finger" like projection in the epidermis
What is the composition of Dermis?
- Dense irregular fibrous connective tissue
- -Tough callagenous fibers
- -Elastic fibers (goes back - like neck of cat)
- -Gel like ground substance (like JELLO)
- -Fibrous network results in elasticity & strength for skin
What are the muscle cells that make up the dermis?
- Smooth muscles usually associated with accesory organs (hair follicles and glands) of the skin
- Striated muscles of the face anchor to the dremis to produce movement & facial expressions (VOLUNTARY)
What are the nerve fibers that that make up the dermis?
- Motor fibers (actions/mechanical) that carry impulses to dermal muscles and glands
- Sensory fibers (feeling/smelling) that carry information back to the central nervous system
Deep pressure sensory fibers of the dermis
Light touch sensory fibers of the dermis
Temperature and pain
Sensory fibers of ther dermis, temp and pain travel on the same pathway
Totoos are created by...
- Thin needle injects ink int eh dermal layer of skin
- Color is permanent because dermal cells do not shed
What is the Subcutaneous layer (hypodermis) composed of?
- (Beneath the dermis)
- Loose fibrous connective tissue
- Collagenous & elastic fibers
- Continuous with those found int he dermis
- No sharp boundary b/t the demis & hypodermis
- Adipose (fatty) tissue
What are the functions of the subcutaneous layer?
- Supplies nutrients to the skin
What are the accessory organs of the skin?
- Hair follicles
- Arrector pili muscles
- Sebaceous gland
- Found everywhere on the body except the palms, soles, lips, nipples, and part of external genitals.
- Group of epidermial cells forming a tube like depression
- Depression extends down into the dermis
- Hair root at the base/bottom
- Nourished by underlying dermal blood vessels
Arrector pili muscles
- Smooth muscle cell attached to each hair follicle
- Hair stands on end with muscle contraction, when a person is cold, or upset, nerve impulses stimulate the muscle to contract and causes goose bumps
- Oil producing gland associated with each hair follicle
- Produce sebum (fatty waste made of a mixture of fatty material and cellular debris/fragments of cells that have died off)
- Secreted into hair follicle through ducts (exocrin)
- Keeps hair & skin soft
- Not found on palms or soles
- Overlies surface of skin or nail bed
- Specialized epithelial cells - continuous with epithelial cells of skin (more keratin = harder)
- White 1/2 moon shaped region
- Most actively growing region
- Cells grow out from this point, keratinize and become part of the nail plate
- Tiny tubes coiled in dermis or subcutaneous tissue
- Coils are lined with sweat secreting epithelial cells
- Eccrine sweat glands
- Apocrine sweat glands
Eccrine sweat glands
- Temperatur regulators
- Found on the forehead, neck and back
- Most numerous sweat gland
- Produces sweat due to increased heat production
- Mostly water but may contain salt, uric acid/urea (waste product)
- Produces sweat on hot days, physical activity and during emitional stress
- Open into a pore
Apocrine sweat glands
- Become active at puberty
- Released with emtional response (sympathetic nervous system/ upset, frightened, pain, and sexual arousal)
- Most numerous in axilla, groin, nipples (develop a scent as they are metabolized by skin bacteria)
- Usually associated with hair follicle
What are the two parts (systems) of the nervous system?
- Central Nervous System (CNS)
- Peripheral Nerous System (PNS) (everything exiting the spinal cord)
Central Nervous System
- Brain (cranial cavity)
- Spinal cord (vertebral cavity)
Is the Central Nervous System doral or ventral?
Dorsal (back, away from belly)
Peripheral Nervous System
Peripheral nerves that connect the CNS to other body parts (think named nerves)
Together they provide sensory (input/feeling), motor (output/doing), and executive integrative functions (what makes you you).
What is a neuron?
- Or Nerve Cell?
- The basic cell of the nervous system
- The most highly specialized cells
- Sensative to changes
What do neurons consist of?
- Cell body (SOMA)
- Dendrites (detect change/many little entenna that receive a signal)
- Nucleus (the brains)
- Axon (myelinated or unmyelinated/long singular string of little cells- prjects away from the nucleus)
- Synaptic know and vesicles (termination button/end of neutron)
What is a 3 layered CT structure that surrounds the brain and spinal cord?
- 3 protective layers (from superficial to deep) are called
- Dura Mater
- Arachnoid Mater
- Pia Mater
What does mater mean?
- Tough mother (one tough mother) covering the brain and spinal cord
- Located closer to the skull
- Most visible
- Tough CT layer that contains numerous blood vessels and is attached in the inner cranial cavity forming the internal periosteum (lots of blood supply)
- Extends into the brain between its lobes (hemospheres) and supports and protects it
- In certain regions it slits into two layers forming dural sinuses (look like veins) which return venous blood from the brain back to the heart.
- The dura extends into the vertebral canal to the level of the sacrum and surrounds the spinal cord
Dura mater and the spinal cord
- Dura mater is the outer most layer of the spinal cord, although it does not attached directly to the vertebrae
- Epidural space between the dura and bony walls
- "Spider mom"
- Thin, web-like membrane lacking blood vessels (although blood vessels pass through it) that is located between the dura mater and pia mater
- "tender mother"
- Thin membrane containing nerves & blood vessels that is directly attached to the brain and spinal cord (shiny & wet looking)
Sub arachnoid space
- Below the spider mother
- located between the arachnoid and pia mater and contain cerebrospinal fluid (CFS) which functions to help protect and nourish the CNS.
A series of interconnected cavities (holes/spaces for fluid) in the cerebral hemispheres (left/right)/brainstems that contain CSF (cerebrospinal fluid) is called?
How many ventricles are there?
- 2 lateral ventricles
- 3rd and 4th are connected by the cerebral aqueduct (canal)
- The 4th ventricle empties into a narrow canal in the middle of the spinal cord and the subarachnoid space of the cerebral meninges
What are the specialized capillaries in the pia mater that project into ventricles and secrete CFS called?
- Choroid plexuses
- The CFS flows through the ventricles, into the central canal of the spinal cord and the subaracnoid space of the cerebral and spinal meninges
Arachnoid granulations are..
...tiny finger like projections (that project from the subaracnoid space into the blood filled dural sinuses) that absorb CFS
What are the functions of CFS?
- Help maintain a stable ionic concentration in the CNS (electrolites, PH/body chemistry)
- Provides a pathway to the blood for waste (transports waste)
- Acts as a shock absorber for the brain
Location of the spinal cord
- Foramen magnum to L2
- It ends at the level of the IVD between L1 and L2 where it is called the conus medullaris
Function of the spinal cord
- Pathway for nerve impulses to and from the brain
- Inferior continuation of the medulla (part of the brainstem) that decends through the spinal canal of the spine
What is the thin connective tissue cord that anchors the conus medullaris tot he coccyx?
Spinl nerves below the conus medullaris are called?
Cauda equina or "horse tail"
Describe the matter of the spinal cord
White mulinated matter that surrounds a core of gray (unmylinated) matter
What makes up the spinal cord?
31 fused segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal) each one producing a pair of spinal nerves (why 8?)
formed by the 8 cervical segments that supply nerves tot he upper limbs
formed by the 5 lumbar segments that supply nerves to the lower limbs
What divides the spinal cord into right and left halves?
The anterior median fissure and posterior median sulcus
What makes up the anterior and posterior horns?
- The core of gray matter forms interneuron/neuron cell bodies
- Anterior horn is formed of neuron cell bodies associated with motor signals
- Posterior horn is formed of interneuron s associated with sensory signal (pain)
- Gray commisure connects the right and left an terior and posterior horns
What are axons?
- Distinct columns (tracts) of nerve fibers formed by the outer layer of white matter
- Anterior funiculus
- Lateral funiculus
- Posterior funiculus
Simplest nerve pathway is called
An area, like a zip code or region
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