Integumentary System: Skin and Epidermis

• The skin is also referred to as the cutaneous membrane.
• Synthesis of vitamin D3 is aided through UV light.
• Sensory receptors in the skin can detect pressure, cold, heat, and vibration.

Epidermis Strata

• The order of the epidermal strata from deep to superficial is: basale, spinosum, granulosum, lucidum, and corneum.
• Keratinocytes are the most abundant cell type in the epidermis and synthesize keratin. They can be alive or dead depending upon their location.
• Tactile cells are used in detecting different objects.
• Skin color is due to a combination of melanin, hemoglobin, and carotene.
• Melanin provides protection against UV light.
• Jaundice results from liver failure and causes bilirubin accumulation in the blood.
• Cyanosis indicates an oxygen deficiency.
• Capillary hemangiomas typically disappear during childhood.

Dermis Components

• The dermis includes sweat glands, hair follicles, collagen fibers, sensory nerve endings, and smooth muscle tissue.
• Blood capillaries that supply the epidermis are located in the dermal papillae.
• Cold temperatures cause vasoconstriction of dermal blood vessels.
• The subcutaneous layer consists of adipose and areolar connective tissue.
• Nails are hard derivatives of the stratum corneum of the epidermis.
• Trimming fingernails involves cutting down the free edge.
• Cutting hair involves trimming the hair shaft.
• Terminal hair forms the beard on males.
• Vellus is the primary fine human hair.
• The arrector pili muscle causes "goosebumps" by pulling on the hair follicle.

Musculoskeletal System

Cartilage

• Fibrocartilage is found in the intervertebral discs.
• Puncturing the auricle of the ear affects elastic cartilage.
• Cartilage functions include supporting soft tissues, serving as a model for bone formation, and forming gliding surfaces at articulations.

Bone

• Bone functions include body movement, hemopoiesis, protection, and mineral storage.
• Hemopoiesis occurs in red bone marrow.
• Bone stores calcium, lipid, phosphate, and fat.
• The metatarsal bone is a long bone.
• Bones of the wrist are short bones.
• The parietal bone is a flat bone.
• The metaphysis of growing bone contains the epiphyseal plate.
• The epiphyseal plate assesses stages of bone growth.
• The medullary cavity of long bone is lined by the endosteum.
• Osteoblasts produce new bone tissue by secreting matrix.
• Osteoclasts break down bone by secreting HCl and enzymes that dissolve the matrix.
• Compact bone is composed of osteons or tubular units.
• In compact bone, concentric lamellae are matrix rings surrounding the central canal of each osteon.
• Canaliculi connect adjacent lacunae, providing pathways for nutrients and other material exchange between osteocytes.
• Each depression on the maxilla and mandible that holds a tooth is called an alveolus.
• Bone markings that serve as an articulating surface include: facet, trochlea, head, and condyle.
• A diarthrosis is a freely mobile joint.
• A synarthrosis is found in the skull sutures.
• The sagittal suture is a fibrous joint.
• An articular capsule is present in synovial joints.
• The pubic symphysis is classified as a cartilaginous joint and an amphiarthrosis.
• Highly stable fibrous joints have low mobility.
• The interosseous membrane between the radius and ulna is a syndesmosis.
• Gomphoses are only found in tooth sockets.
• Fibrocartilage is located between the bones in a symphysis.

Synovial Joints

• Articulating bone surfaces are covered with articular cartilage.
• Ligaments reinforce joints.
• Synovial fluid is secreted by the synovial membrane.
• Fibrous articular capsules enclose synovial joints.
• Bursae are fluid-filled sacs that cushion synovial joints.
• An interphalangeal joint moves in one plane and is a uniaxial joint.
• Ball-and-socket joints are multiaxial.
• Eversion involves turning the sole of the foot laterally.

Muscle Cells

• Muscle cell characteristics: contractility, extensibility, excitability, elasticity, and conductivity.
• Skeletal muscle functions include maintaining posture, performing coordinated and localized movements, regulating temperature, supporting body organs, and restricting movement of materials through body tracts.
• The hierarchy of skeletal muscle components from smallest to largest is myofibrils, muscle fiber, fascicle, then skeletal muscle.
• Connective tissue layers of a skeletal muscle from superficial to deep: epimysium, perimysium, endomysium.
• Tendons attach muscle to bone.
• Myosin makes up thick filaments.
• In a sarcomere, the Z disc appears as a thin, dark line in the middle of an I band.
• The distance from Z disc to Z disc is the length of a sarcomere.
• The H zone is the region within the A band that contains only thick filaments.
• The narrow space between the motor neuron and muscle fiber in a neuromuscular junction is the synaptic cleft.
• Muscle fibers concentrically arranged describe the pyloric sphincter.
• Pennate muscles resemble a feather.

Muscle Atrophy

• Muscle atrophy results in fibers wasting away and dying, muscle losing tone, fibers becoming weaker, and muscle size reducing.
• The articulation between the skull and first vertebra acts as a first-class lever.
• Extension of the knee when the quadriceps muscles contract, moving the knee joint is an example of a 3rd-class lever.
• Using the mandible to close the mouth while biting on food is a an example of a third-class lever.
• Synergist muscles assist the agonist, may stabilize the point of origin, and may contribute to tension at the insertion site.
• A forearm muscle named flexor digitorum profundus is located deep.
• Pollicis refers to the thumb.
• Orbicularis oris is circular.
• Triceps brachii has three muscle heads or tendons of origin.
• In the resting stage, a muscle with "rectus" in its name has straight fascicles.
• Smooth muscle fibers have a single nucleus and thick/thin filaments, but no Z discs.
• Smooth muscle tissue is found in the organs of the digestive tract, the walls of blood vessels, and the iris.
• Cardiac muscle tissue has striated cells that form Y-shaped branches.

Nervous System

• The brain and spinal cord make up the central nervous system. The peripheral nervous system consists of everything else.
• A nerve is a cable-like bundle of parallel axons.

Functions

• The functions of the nervous system are collecting information, processing and evaluating information, and responding to information.
• The afferent division is also known as the sensory division.
• Afferent refers to the conduction of sensory impulses toward the CNS.

Motor Division

• The motor division conducts output from the CNS, facilitates voluntary control of skeletal muscle, involuntary control of the heart, and transmits impulses to muscles and glands.
• The somatic sensory division conducts impulses from the skin, joints, skeletal muscles, and special senses.
• The somatic motor division has voluntary control over skeletal muscles.
• Glial cells and neurons form nervous tissue.
• Neurons do not have a high mitotic rate.
• The cell body is responsible for receiving, integrating, and sending nerve impulses.
• Multipolar neurons are the most common structural type of neuron.
• Glial cells are smaller and capable of mitosis, unlike neurons.
• Ependymal cells circulate cerebrospinal fluid.
• Oligodendrocytes myelinate and insulate axons within the CNS.
• Each oligodendrocyte can form a myelin sheath around many axons simultaneously.
• Astrocytes help to form the blood-brain barrier and have perivascular feet that wrap around capillaries in the CNS.
• Neurolemmocytes myelinate and insulate axons in the peripheral nervous system.
• Each neurolemmocyte can wrap only a 1mm portion of a single axon.
• The connective tissue wrappings of a nerve from outermost to innermost are epineurium, perineurium, then endoneurium.
• Perineurium surrounds bundles (fascicles) of axons.
• The common structural types of synapses are axosomatic, axodendritic, and axoaxonic.
• Axodendritic synapses are the most common structural type of synapse.
• A converging circuit is a type of neural circuit in which several nerve impulses come together at a single postsynaptic neuron.
• A reverberating circuit uses feedback to produce repeated, cyclical stimulation.
• A diverging circuit spreads information from one presynaptic neuron to several postsynaptic neurons.

Circulatory System

• Gas, nutrient, and waste exchange occur between the capillaries and the tissues of the body.
• As an arterial pathway moves farther from the heart, the arteries get smaller.
• As a venous pathway moves closer to the heart, the veins get larger.
• The tunica intima comprises an endothelium and a subendothelial layer of areolar connective tissue.
• The tunica media consists of circularly arranged layers of smooth muscle cells.
• In arteries, the tunica media is the thickest layer of the wall.
• The largest arteries of the body are classified as elastic arteries.
• Order of artery types for passage of blood from the heart to capillaries: elastic arteries, muscular arteries, then arterioles.

Precapillary Sphincters

• Precapillary sphincters close when the tissue’s needs have been met, cause blood to flow directly from the metarteriole into the postcapillary venule, and open when the tissue needs nutrients.
• They control blood flow into the true capillaries.
• Valves in veins cause venous blood flow to go in only one direction.
• Contraction of skeletal muscles plays an essential role in the movement of blood in veins.

Explore the integumentary system, focusing on the skin's layers and functions. Learn about vitamin D3 synthesis, sensory receptors, and epidermal strata. Understand the roles of keratinocytes, tactile cells, and pigments like melanin in skin color and protection.