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23 Cards in this Set
- Front
- Back
Bone is composed of?
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- Hard connective tissue composed of osteocytes and a mineralized matrix
- Matrix provides strength to bone. -- Organic: collagen fibers -- Inorganic: hydroxyapetite (calcium and phosphate). - Osteocytes located in lacunae -- Cancellous or spongy bone -- Compact bone |
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How does Cancellous bone differ from other types?
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- Cancellous or spongy bone has numerous empty spaces between the supportive trabeculae
- Has the appearance of a natural sponge - Spongy bone located within the body of the bone, pores contain red bone marrow |
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How does Compact bone differ from other types?
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- compatct bone is arranged in concentric layers around a central canal which contains a blood vessel.
- The osteoblast deposits the mineral matrix and collagen fibers. Once this cell is surrounded by the matrix, it is called an osteocyte - All bony tissue is enclosed within a layer of connective tissue (periosteum) |
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What is blood composed of?
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- Plasma
-- Liquid matrix which lacks protein fibers - Formed elements: red cells, white cells, and platelets - Hemopoietic tissue -- Red bone marrow forms the blood cells |
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What are the functions of the integument?
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Functions:
- Protection - nonspecific immunity and prevents desiccation - Sensory - highly sensitvie to the external environment - Thermoregulation - accomplished by vasodilation, vasoconstriction, and insulation - Vitamin D synthesis - precursor to the hormone calcitrol (calcium absorption) |
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What are the three layers of the integument? (histology)
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- Epidermis - keratinized stratified squamous epithelium
- Dermis -- Papillary layer - aerolar c.t. (20%) -- Reticular layer - dense irregular c.t. (80%) -Hypodermis - superficial fascia, adipose tissue, areolar c.t. and blood vessels. ***Not part of the integument. |
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Describe the characteristics of the epidermis
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- composed of keratinized stratified squamous epithelium
- avascular, typical for all epithelial tissue - arranged in 4 or 5 distinct histological layers (strata) - Cell types include: -- Keratinocytes -- Melanocytes -- Merkel cells -- Langerhans cells - Between 35-45 days entire epidermal layer will regenerate |
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What cell types are found in the integument?
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- Keratinocytes represent 90% of all cells, secrete the protein keratin
- Melanocytes secrete melanin, provides protection from ultra-violet radiation. - Merkel cells serve as sensory receptors to touch - Langerhans cells (epidermal dendritic cells) originate from bone marrow and migrate to the epidermis. Part of the immune system, engulf foreign antigens) |
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Layers of the epidermis: Stratum basale - Describe
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Layers of the epidermis: stratum basale:
- Deepest epithelial layer or strata - A single layer of cells which undergo continuous replication (mitosis). - Merkel cells and melanocytes also located with this layer - The protein melanin shields the basal cell nuclei from U.V. radiation, which damage the DNA molecule and disrupt normal cellular replication. - Merkel cells associated with underlying sensory neurons (touch). |
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Layers of the epidermis: Stratum spinosum - Describe
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- Characteristic spiny appearance as a result of cell-cell contact (desmosomes).
- Several cell layers in thickness. - Cells begin to transport the secreted melanin protein into intracellular compartment. - Langerhans cells also located within this layer. |
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Layers of the epidermis: Stratum granulosum - Describe
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- Thin layer (3-5) of flattened keratinocytes
- Cell membranes thicken, cells flatten, organells and nucleus disintegrate - Gradually cells begin to die as they become more superficial - The process of keratinization begins, cells contain granules of keratin - A glycolipid is secreted into the extracellular space and functions as a waterproofing agent (prevents desiccation). |
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Layers of the epidermis: Stratum lucideum - Describe
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- Occurs only on the soles of the feet and the palms of the hands (thick skin).
- Appears as a thin clear zone under the microscope (3-5 cell layers). - In other anatomical regions this layer is absent and is called thin skin. |
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Layers of the epidermis: Stratum corneum - Describe
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- The most superficial layer, represented by 25-30 cellular layers of dead flattened keratinocytes
- Cells contain an abundance of keratin - This layer protects the underlying layers of the integument from abrasiona nd penetration of foreign bodies. - cells of this layer are continually shedding |
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Describe the structure of the dermis
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- Represented by connective tissue, collagen and elastic fibers, fibroblasts, macrophages, blood vessels, sensory receptors, glands, and hair follicles
- Based on histology is separated into two layers: -- Superficial papillary layer -- Deep reticular layer - Sensory funcitons: pain, itch, tickle, temperature, touch, pressure, two-point discrimination |
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Describe the papillary layer of the dermis
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- This layer is composed of aerolar connective tissue
- Contains peg-like projections called dermal papillae which contribute in the formatino of epidermal ridges - The epidermal ridges increase surface area/friction and improves the grip of the hands & feet - Oil and sweat residues associated with friction ridges generate fingerprints |
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Describe the composition of the reticular layer
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- Composed of dense irregular connective tissue
- Contains an abundance of the collagen fibers which give the skin its strength - Separations or less dense areas between bundles of collagen fibers are called cleavage or tension lines - Elastic fibers also located in this layer, allows for stretch and recoil of the skin |
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Describe sweat glands
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- Also known as sudoriferous glands, are distributed over the entire skin except the nipple and external genitalia
- Sweat is 99% water and sodium chloride and traces of urea, ammonia, and uric acid - Two types: eccrine and apocrine |
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What discriminates Eccrine glands?
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- Eccrine also known as merocrine are more numerous on the palms, soles of the feet, and forehead.
- The glandular tissue is located within the dermis, the duct of an eccrine sweat gland opens directly to the skin surface. - Essential for thermoregulation, sweating is regulated by the sympathetic nervous system |
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What discriminates Apocrine glands?
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- Apocrine sweat glands confined to the axillary and genital regions
- Ducts of apocrine glands open onto hair follicles, similar secretions as eccrine glands but have addition of lipids and proteins - Becomes functional at puberty under the influence of sex hormones, no role in thermoregulation |
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What discriminates Sebaceous glands
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- Located over entire body except thick skin of palms and soles.
- Most of all sebaceous glands develop from the hair follicle, the oil or sebum is secreted directly onto the hair follicle. - Sebum will soften and lubricate the skin, keeping it from cracking - Secretions of sebum is stimulated by hormonal activity |
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Describe the composition of the hypodermis
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- Composed of aerolar connective tissue and adipose tissue.
- Also known as superficial fascia - Attaches the dermis to underlying muscle and bone - Is the site of deposition for adipose (fat) - Functions as an insulator (retains body heat) |
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Describe the composition of hair
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- consists of dead keratinized cells originating from the hair bulb (epidermal derivative)
- Found everywhere on the human body except palms, soles, lips, nipples, and parts of external genitalia. - Hair represented by three concentric layeros of dead cells, the medulla, the cortex (color) and cuticle - Hair shaft protrudes above skin surface - Hair root located below surface; base of root is the harb bulb (germinal layer) - Sensory nerve endings associated with hair bulb, sensitive to touch |
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Describe the composition of nails
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- Modified keratinized epidermal cells on the distal ends of digits
- Homologous with claws and hooves - Represented by: free edge, body, and root (embedded in skin) - Nail root (matrix) responsible for growth |