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Describe the basic structure of skin.
The skin consists of two main layers:
Epidermis – Superficial layer made of keratinized stratified squamous epithelium. It is avascular and provides protection.
Dermis – Deeper connective tissue layer containing blood vessels, nerves, glands, and hair follicles.
Below the skin is the hypodermis (subcutaneous layer), composed mainly of areolar and adipose connective tissue. It is not technically part of the skin but anchors it to underlying structures.
Describe the layers and basic structure and components of the dermis.
The dermis has two layers:
Papillary layer
Areolar connective tissue
Contains dermal papillae
Capillaries & sensory receptors
Reticular layer
Dense irregular connective tissue
Contains collagen & elastic fibers
Houses glands, hair follicles, blood vessels
Explain the process by which hair and nails grow.
Hair grows from mitotic activity in the hair matrix. Cells keratinize and push upward.
Hair growth cycle:
Anagen (growth)
Catagen (transition)
Telogen (resting)
Nails grow from the nail matrix through continuous mitosis and keratin production.
Describe the inorganic and organic components of the extracellular matrix of bone tissue.
Organic component (osteoid):
Collagen fibers
Proteoglycans
Provides flexibility and tensile strength
Inorganic component:
Hydroxyapatite (calcium phosphate crystals)
Provides hardness and resistance to compression
Describe how bones are classified.
Bones are classified based on shape:
Long bones – Longer than wide (e.g., femur).
Short bones – Cube-shaped (e.g., carpals).
Flat bones – Thin and flattened (e.g., sternum).
Irregular bones – Complex shapes (e.g., vertebrae).
Sesamoid bones – Develop within tendons (e.g., patella).
Describe the basic functions carried out by the components of the integumentary system.
The integumentary system functions include:
Protection (barrier against pathogens, UV light, dehydration)
Temperature regulation (sweat glands, blood vessel dilation/constriction)
Sensation (touch, pain, pressure receptors)
Vitamin D synthesis
Excretion (small amounts of waste through sweat)
Immune defense (Langerhans cells)
Explain the functions of the dermal papillae.
Dermal papillae:
Increase surface area for attachment
Strengthen epidermal–dermal connection
Form epidermal ridges (fingerprints)
Contain capillary loops for nourishment
Explain the composition and function of sweat and sebum.
weat:
99% water
Electrolytes
Urea & uric acid
Function: cooling & waste removal
Sebum:
Lipid-rich oily substance
Function: lubricates skin & hair, antibacterial
Explain the differences between primary and secondary bone.
r:
Primary (woven) bone:
Forms first during development
Collagen fibers randomly arranged
Weaker
Secondary (lamellar) bone:
Replaces woven bone
Organized collagen fibers
Stronger and more durable
Describe the general process of bone repair.
Hematoma formation – Blood clot forms.
Fibrocartilaginous callus formation – Soft callus forms.
Bony callus formation – Spongy bone replaces soft callus.
Bone remodeling – Compact bone restores original shape.
: Explain how the cells of the epidermis are arranged into layers.
The epidermis is arranged into strata (layers) from deep to superficial:
Stratum basale – Mitotically active stem cells
Stratum spinosum – Keratinocytes connected by desmosomes
Stratum granulosum – Keratinization begins
Stratum lucidum – Present only in thick skin
Stratum corneum – Dead, keratinized cells
Explain how skin markings such as epidermal ridges are formed.
Epidermal ridges are formed by projections of dermal papillae pushing into the epidermis during fetal development. These create friction ridges (fingerprints), which are genetically determined and unique.
Explain how to classify burns and how to estimate their severity.
Burn Classification:
First-degree: Epidermis only
Second-degree: Epidermis + partial dermis
Third-degree: Full thickness (epidermis & dermis destroyed)
Severity estimation:
Rule of Nines (percentage of body surface area)
Patient age
Burn depth
Explain the functions of the three main cell types in bone tissue.
Osteoblasts – Build bone (secrete matrix).
Osteocytes – Maintain bone tissue.
Osteoclasts – Break down bone (resorption).
Explain the differences between red and yellow bone marrow.
Red Bone Marrow
*Produces blood cells
*Found in spongy bone
*Highly vascular
Yellow Bone Marrow
*Stores fat
*Found in medullary cavity
*Less vascular
In children, marrow is mostly red; in adults, much converts to yellow.
: Describe the cells of the epidermis and the life cycle of a keratinocyte.
Epidermal cell types:
Keratinocytes – Produce keratin
Melanocytes – Produce melanin
Langerhans (dendritic) cells – Immune defense
Merkel cells – Touch receptors
Life cycle of a keratinocyte:
Formed in stratum basale
Pushed upward
Accumulate keratin
Die and flatten
Shed from surface (about 4 weeks)
Explain how melanin is produced and its role in the integument.
Melanin is produced by melanocytes in the stratum basale from the amino acid tyrosine via the enzyme tyrosinase.
Melanin:
Protects DNA from UV radiation
Contributes to skin, hair, and eye color
Determines skin tone based on amount and distribution
: Describe the functions of the skeletal system.
The skeletal system performs several essential functions:
Support – Provides structural framework for the body.
Protection – Protects vital organs (e.g., skull protects brain, ribs protect heart and lungs).
Movement – Bones act as levers for skeletal muscles.
Mineral storage – Stores calcium and phosphate.
Blood cell formation (hematopoiesis) – Occurs in red bone marrow.
Fat storage – Yellow bone marrow stores triglycerides.
Hormone production – Osteocalcin helps regulate blood sugar and fat deposition.
Describe the gross structure of long, short, flat, irregular, and sesamoid bones.
Long Bone Structure:
Diaphysis (shaft)
Epiphyses (ends)
Medullary cavity
Articular cartilage
Periosteum
Endosteum
Short Bones:
Spongy bone with thin outer compact bone.
Flat Bones:
Two layers of compact bone with spongy bone (diploë) between.
Irregular Bones:
Spongy bone surrounded by compact bone.
Sesamoid Bones:
Small, round bones embedded in tendons.
Describe the three main types of cancerous skin tumors.
:
Basal Cell Carcinoma
Most common
Least dangerous
Rarely metastasizes
Squamous Cell Carcinoma
Arises from keratinocytes
Can metastasize
Melanoma
Most dangerous
Originates from melanocytes
High metastatic potential
Describe how thick skin and thin skin differ.
Thick Skin
Thin Skin
Found on palms & soles
Covers rest of body
Has stratum lucidum
No stratum lucidum
Thicker epidermis
Thinner epidermis
No hair follicles
Has hair follicles
Describe the other pigments that contribute to skin color.
Carotene – Yellow-orange pigment from diet
Hemoglobin – Red pigment in blood
Oxyhemoglobin – Bright red (oxygenated)
Deoxyhemoglobin – Dark red (low oxygen)
Explain how skin coloration may indicate pathology.
Cyanosis
*Bluish
*Low oxygen
Jaundice
*Yellow
*Liver dysfunction (bilirubin buildup)
Pallor
*Pale
*Reduced blood flow
Erythema
*Red
*Increased blood flow
Bronzing
*Bronze
*Addison’s disease
Describe the structure and function of hair and nails.
Hair:
Shaft (above surface)
Root (below surface)
Bulb (growth region)
Hair follicle surrounds root
Function: protection, sensation, temperature regulation
Nails:
Nail plate
Nail bed
Matrix (growth area)
Function: protect fingertips, enhance grip
Summarize the structural properties of sweat and sebaceous glands.
Sweat glands:
Eccrine (merocrine) – Widely distributed, watery sweat
Apocrine – Axillary & groin regions, thicker secretion
Sebaceous glands:
Holocrine glands
Secrete sebum into hair follicles