A+P Flashcards
***Four Types of Human Tissue
(1) Muscle Tissue
(2) Nervous Tissue
(3) Epithelial tissue
(4) Connective Tissue
Functions/characteristics of Muscle Tissue
(a) Generates the physical force to make the body structures move
(b) Arranged in bundles
(c) Contractile cells that provide the ability to move the body in three dimensions
(d) Well supplied with blood vessels (lots of energy & waste requirements).
Functions/characteristics
of Nervous Tissue
(a) Detects changes inside/outside the body
(b) Initiates & transmits nerve impulses that coordinate body
*** Functions/characteristics of Epithelial tissue
(a) Integumentary System
(b) Epithelium:
(c) Epithelial Tissue:
Functions/characteristics
of Connective Tissue
(a) Protects and supports the body and its organs
(b) Binds organs together
(c) Stores energy reserves as fat
(d) Provides immunity
1) Skin, Hair, Nails
2) Accessory Structures
Integumentary System
1) Medical term for skin and main portion of the integumentary system.
Epithelium:
1) Covers body surfaces; lines body cavities, hollow organs and ducts (tubes); and forms glands
(c) Epithelial Tissue:
(1) They provide contact or adhesion between neighboring cells or between a cell and extracellular matrix.
(2) They maintain paracellular barrier of epithelia (barrier in between cells) and control transport of materials or signals between cells (paracellular transport).
(3) Cell junctions are dense in epithelial tissues because the tissue needs to maintain both
strength and integrity in a wide variety of conditions.
Cell Junction
Form barrier against water and antigens passing between individual epithelial cells
Tight Junctions
Cell-cell adhesions continuously assembled & disassembled so cells can respond changes in their microenvironment.
Adherens Junctions
Form stable adhesive junctions between cells.
Desmosomes
Allows various molecules & electrical signals to pass freely between cells
Gap Junctions
Facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane.
Hemidesmosomes
***Epithelial tissue is broadly categorized as either:
(a) Covering and lining epithelium
(b) Glandular epithelium
Covering and lining epithelium:
(a) Covers external surfaces of the body and some internal organs
(b) Lines body cavities, blood vessels, and ducts
(c) Lines interior of respiratory, GI, urinary and reproductive systems
(d) Integral part of sense organs for hearing, vision and touch
Secreting portion of the glands, such as sweat glands
Glandular epithelium
***Most superficial layer of cells
Apical
***Deepest layer of the cell
Basal
- **(a) Thin extracellular structure composed mostly of protein fibers
- **(b) Located between the epithelium and underlying connective tissue layer
- **(c) Helps to bind and support the epithelium
Basement membrane
2 ways of classifying epithelial tissue:
Morphology
Stratification
Classification of epithelial cells based on shape
Morphology
Classification of epithelial cells based on number of layers
Stratification
***Shaped like pancakes
Squamous
***Shaped like the tesseract in Captain America
Cuboidal
***Shaped like the column block in Tetris
Columnar
***Changes shape like the T-1000 in T2: Judgement Day
Transitional
- **(1) Thin, flat shape allows rapid passage of substances through them
(2) Can be keratinized or non-keratinized; “wet” or “dry” depending on their location in the body
(3) Found in areas such as the lining of the esophagus, mouth and cervix
Squamous Epithelium
(1) Tall as they are wide and shaped like cubes or hexagons
(2) Frequently have microvilli at apical surface
(3) Function in either secretion or absorption
(4) Found in areas such as the salivary glands and thyroid follicles
Cuboidal Epithelium
(1) Taller than they are wide
(2) Protect underlying tissues
(3) Apical surfaces may have cilia or microvilli
(4) Often specialized for secretion and absorption
(5) Lines most organs of the GI tract, respiratory tract, and fallopian tubes
Columnar epithelium
(1) Able to change shape from flat to cuboidal and back depending on tension & distention of tissue.
* **(2) Useful for organs such as the urinary bladder, when it is stretching (distend) to a larger size and then as it collapses to a smaller size.
Transitional Epithelium
**(1) A single layer of cells that functions in a diffusion, osmosis, filtration, secretion and absorption.
**(2) Secretion: production and release of substances
**(3) Absorption: intake of fluids or other substances
**(4) Osmosis: movement of water across a semipermeable membrane from an area of lower
solute concentration to an area of higher solute concentration.
***(5) Diffusion: movement of particles from an area of high concentration to an area of low Concentration
Simple Epithelium
- **(1) Pseudo (false) stratified (layered)
- **(2) It is simple epithelium that appears be stratified because the nuclei lie at different levels & not all cells reach the apical surface.
- **(3) However, it is still simple epithelium because all the cells rest on the basement membrane.
(a) Cells that extend to the apical surface may contain cilia - **(4) One specialized type of pseudostratified cell are goblet cells, which secrete mucus and are an integral part of mucous membranes.
Pseudostratified Epithelium
(1) Cilia provide two forms of locomotion depending on the cell:
(a) Movement of the cell itself (like bacteria) or some parasites ***
(b) Movement of particles or substances across or around the cell
(2) In mammals, cilia help remove contaminants or move particles by moving fluids over the cell layers.
(a) The lining of the nasopharynx and the trachea are covered in cilia to remove mucus, bacteria, and other debris from the lungs.
(b) Fallopian tubes are lined with cilia to assist in helping fertilization by moving the egg towards the uterus.
Ciliated Epithelial Cells
1) increase the surface area of a cell by multiplying the area from 2 dimensions to 3
dimensions. **
(2) on cellular surfaces enable the absorption and secretion of far more nutrients/material because they expand the active surface area by orders of magnitude.
(3) Other uses:
(a) Help anchor sperm to the egg and allow for easier fertilization.
(b) In white blood cells, ___ act as an anchoring point and aid in the migration of white blood cells.
(c) ___on other cell surfaces may sweep unwanted materials toward an absorptive area of the cell.
Microvilli on Epithelial Cells
a highly-insoluble fibrous protein with water-proofing qualities & high friction resistance.
Keratin
Epithelial cells infused with keratin in the stratum basale of the epidermis are called
Keratinocytes
Keratinocytes lose their nucleus and organelles to make room for keratin. Are they still living
No
Keratinized or non-keratinized:
(a) Found on wet/interior surfaces exposed to considerable wear & tear.
(b) Found in the lining of mouth cavity, tongue, pharynx, esophagus and vagina.
Non-keratinized epithelium
Keratinized or non-keratinized:
(a) Found on dry/outer surfaces where resistance to both friction & water is needed.
(b) Outer epidermis consists of keratinocytes that provide protection against water, friction,
abrasion, and microorganisms.
Keratinized stratified epithelium
(1) Supports & physically connects other tissues/cells together to form the organs of the body.
Connective Tissue
↑ cells ↓ extracellular space (matrix)
Epithelial
↓ cells ↑ extracellular space (matrix)
Connective
Connective tissues typically have three components:
(a) Resident Cells
(b) Extracellular Matrix (ECM)
(c) Protein fibers
extracellular material produced by the connective tissue cells embedded within it
Matrix
Major component of the matrix is
ground substance crisscrossed by protein fibers
CT CELLS
(1) Most common cells in connective tissue
(2) Produce & maintain most of the tissue’s extracellular components
(3) Synthesizes & secretes collagen** and elastin
(4) Major component of the reparative capacity of connective tissue
Fibroblasts
CT CELLS
(1) AKA fat cells or adipose cells or adipose tissue
(2) Specialized for cytoplasmic storage of lipid as neutral fats, or less commonly for production of heat. ***
(3) Large population of adipocytes (adipose connective tissue) serves to cushion and insulate the skin and other organs.
Adipocytes
CT CELLS
(1) Components of loose connective tissues, often located near small blood vessels in the skin.
(2) Function in localized release of compounds important to inflammatory response, innate immunity, and tissue repair.***
Mast Cells
CT CELLS
(1) Abundant (25% of all protein in body) ***
(2) Very strong and resistant to shear forces
(3) Key element of all connective tissues, as well as epithelial basement membranes
Collagen Fibers
CT CELLS
(1) Composed of elastin
(2) Strength and elasticity
(3) Have rubberlike properties that allow tissue containing these fibers to be stretched or distended and return to their original shape.
Elastic Fibers
CT CELLS
(1) Compromised of glycogen and glycoprotein (2) Provide strength and support in the walls of small blood vessels **
(3) Stroma supporting framework of many soft organs; most notably the immune system, liver, endocrine glands, spleen, lymph nodes
Reticular Fibers
(1) Line entire GI, respiratory, reproductive, and much of the urinary system.
(2) Epithelial layer secretes mucous (mucin) via goblet cells.
Mucous Membranes
Mucous Membrane functions:
(a) General: Prevents cavities from drying out
(b) Resp: traps particles in the respiratory tract
(c) GI: lubricates and absorbs food as it moves through the tract, secretes digestive enzymes
(d) Derm: helps bind the epithelium to underlying structures
Lines body cavity that doesn’t open directly to exterior & covers organs that lie within the cavity.
Serous Membranes
Serous Membranes
Attached to cavity wall
Parietal
Serous Membranes
Part that covers and attaches to the organs
Visceral
Serous Membranes
Secretes serous fluid and provides lubrication for organ movement
Mesothelium
Serous Membranes
Lining thoracic cavity and covering the lungs.
Pleura
Serous Membranes
Lining the heart cavity and covering the heart.
Pericardium
Serous Membranes
Lining abdominal cavity and abdominal organs
Peritoneum
(1) Lines joints.
(2) Composed of areolar connective tissue and adipose tissue with collagen fibers.
(3) No epithelial layer.
(4) Secrete synovial fluid.
Synovial Membranes
This fluid reduces friction, lubricates & nourishes cartilage, and removes microbes/debris from the joint cavity
Synovial fluid
Layers of the Skin
(1) Epidermis
(2) Dermis
(3) Subcutaneous (hypodermis)
(1) Surface layer
(2) Comprised of epithelial tissue
Consists primarily of continually regenerating keratinocytes
(a) Different layers of the epidermis represent keratinocytes at differing stages in their
approximately 30-day lifecycle.
(b) Epidermal Thickness varies by location and age:
(3) 75 to 150 µm in thin skin (eyelids) to 0.4 to 1.5 mm in thick skin (palms and soles)
(a) Epidermis lacks any vascular structures & obtains all nutrients from the dermal vasculature by diffusion
Epidermis
(1) Lies inferior/deep to the epidermis
(2) Comprised of connective tissue
(a) Primarily consists of dense irregular connective tissue and functions to cushion the body from stress and strain
(3) A basement membrane always occurs between the stratum basale of the epidermis and the dermis
(4) Nutrients for keratinocytes diffuse into the avascular epidermis from the dermal vasculature through the basement membrane
Dermis
(a) Lies inferior/deep to dermis
(b) Is not part of the skin
Subcutaneous (hypodermis)
Layers of the Epidermis
(1) Stratum Corneum
(2) Stratum Lucidum
(3) Stratum Granulosum
(4) Stratum Spinosum
(5) Stratum Basale
Layers of the Epidermis
(a) Cells consist mostly of keratin
(b) Cells are shed & replaced from below
Stratum Corneum
Layers of the Epidermis
(a) Found only in palms & soles of hands & feet
Stratum Lucidum
Layers of the Epidermis
(a) Losing cell organelles and nuclei
(b) Infusion of waterproofing lipids
Stratum Granulosum
Layers of the Epidermis
(a) Cells beginning to flatten
Stratum Spinosum
Layers of the Epidermis
(a) Stem cell layer; new cells arise here
Stratum Basale
Layers of the Dermis
(1) the layer of the dermis directly underneath the
epidermis
(a) Contains the terminal endings of capillaries, lymph vessels and sensory neurons. These extend from the dermis toward the epidermis in the dermal papillae
Papillary layer (loose areolar tissue)
Layers of the Dermis
(1) is thicker than the overlying papillary dermis; comprised of a dense concentration of collagenous, elastic, and reticular fibers that weave throughout it
(a) These protein fibers give the dermis its strength, extensibility, and elasticity
(b) Within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels
Reticular layer
(1) Specialized cells of the epidermis & hair follicle; primary function is synthesis and transfer of melanin to adjacent keratinocytes
Melanocytes
(1) Touch and pressure are sensed by four types of mechanoreceptors in the skin
(2) expanded dendritic endings in epidermis of glabrous skin that respond to sustained pressure and touch
(3) Consist of tactile disc and neuron for touch sensation
Merkel Cells
(1) Typically found within the stratum spinosum
(2) Form a mobile and dense network of cells that samples any antigens that attempt to pass through the epidermis
(3) These monocyte-derived cells represent a large part of the skin’s adaptive immunity
Dendritic Cells
(1) Found on most skin surfaces except palmar surfaces of hands/fingers or plantar surfaces of feet/toes
(2) comprised of fused keratinized cells Surrounded by the hair follicle
(3) Genetic/hormonal influences largely determine pattern/distribution of hair
(4) Protection for the scalp, eyes, and nostrils
Hair
Release secretions directly into the bloodstream
Endocrine glands:
Release secretions onto an epithelial surface via a duct
Release secretions onto an epithelial surface via a duct
(a) Sebaceous
b) Sudoriferous (sweat glands
Derm-specific exocrine glands:
An exocrine gland in the skin that opens into a hair follicle and secretes an oily/waxy sebum lubricates the hair in humans and other mammals
(2) Found in all areas of the skin except the palms of the hands and soles of the feet
(3) work in conjunction with apocrine glands in thermoregulation
Sebaceous Glands
(1) Cover nearly the entire body surface; especially dense on the palms, soles, forehead, and upper limbs (500/cm2)
(2) Empty directly onto the skin surface, not from hair follicles
(3) Serves as major thermoregulation component of the integumentary system
(4) Sweat is a dilute electrolyte solution comprised of H2O, NaCl, and minimal waste products
(5) Minimal Odor from eccrine sweat
Sudoriferous – Eccrine Glands
(1) Largely confined to the axillae, perineum, and concentrated in hairy areas
(2) Attached to the hair follicle; sweat empties onto the skin via the follicle opening
(3) sweat is cloudy, viscous, and initially odorless. However, serves as a nutrient source for microbes and attains its characteristic odor upon being degraded by bacteria.
(4) do not become functional until puberty and have a hormonal activation pattern
Sudoriferous – Apocrine Glands
Distal margin of nail plate
Free edge:
(1) Portion of the nail that is visible; colored pink because of underlying capillaries
(a) Surrounded by a soft tissue border known as the lateral and proximal nail folds
Nail body (plate)
Visible part of the matrix; whitish crescent at base of nail plate
Lunula (little moon)
Semi-circular layer of epithelial cells (stratum corneum) covering the proximal portion of nail plate
Cuticle
Thickened area of stratum corneum beneath the free edge that attaches the free edge to the fingertip
Nail bed
Portion of the nail that is not visible
Nail root
Proximal portion of the epithelium deep to the nail root where new nail cells are produced
Nail matrix
Nails – Function
(a) Protects distal phalanxes & surrounding soft tissues from injuries
(b) Enhances precise & delicate finger movements by exerting counter-pressure on pulps of the fingers when grasping and manipulating objects
(c) Enables “extended precision grip” for pulling, and certain cutting or scraping actions
Actual nail growth rate is highly dependent on
age, sex, season, exercise level, diet, and
other factors
Fingernails grow approx. ____ per month & require _____ to regrow completely
3.5 mm
3-6 months
Toenails grow approx. ___ per month & require ____ to regrow completely
1.6 mm
12-18 months
Lack of oxygen in the blood will make the skin appear
bluish or cyanotic (cyan = blue)
due to a buildup of the yellow pigment bilirubin, indicated liver disease
Jaundice (jaund = yellow)
due to an engorgement of capillaries in the dermis with blood.
Due to skin injury, exposure to heat, inflammation, or allergic reaction
Erythema (eyth = red)
may occur in condition such as shock and anemia
Pallor or paleness
There are three main pigments that influence skin pigmentation:
(a) Melanin (epidermis)
(b) Carotene (dermis)
(c) Hemoglobin (red blood cells within capillaries of dermis)
(1) High melanin rate =
(2) High carotene rate =
(3) High hemoglobin rate =
darker brown to black skin tones
yellow to reddish tones
red to pinkish tone
(1) Primary determinant of skin color, hair color and eye color
(2) Causes the skin color to vary from pale yellow to reddish-brown to black
Melanin
yellow colored, lipid-soluble compounds found in red, orange, yellow and green vegetables and fruit.
Carotenoids
Excessive intake of these foods can cause Carotenemia:
(a) Characterized by yellow-orange discoloration of the skin
The skin color can return to normal with dietary modification
the iron-containing oxygen-transport protein in erythrocytes (red blood cells)
Hemoglobin
- (2) Sudden drop in oxygenation can affect skin color, initially causing pallor
(3) Prolonged decreased oxygen levels increases deoxygenated hemoglobin, subsequently causing cyanosis
UV light exposure stimulates
melanin production; increasing both the amount and darkness of the melanin pigment imparted into the epidermis
UV overexposure is a predisposing factor for
skin cancer
(1) A genetic (recessive-inherited) condition characterized by little or no melanin pigment in the eyes, skin or hair
(2) Occurs worldwide and affects people of all races. Males and females alike can have the condition.
Albinism
Main health complications or albinism consist of:
(a) Sunburns easily during UV exposure
(b) Increased risk for skin cancer over their lifetime
(1) Acquired depigmentation the skin characterized by loss of melanocytes
(2) Affects 0.5–1% of the population and occurs in all races, however, far more dramatic presentation in darker skinned individuals
(3) Thought to be a systemic autoimmune disorder in which antibodies attack the melanocytes
Vitiligo
How do tattoos work
(1) Pigment injected through the epidermis and activates an immune response, resulting in phagocytes & macrophages engulfing pigment particles
(2) Macrophages containing the pigment in the papillary dermis are trapped in the collagen matrix, forming a homogenized layer below the dermal/epidermal boundary
(3) The trapped pigment particles in the papillary dermis are stable, however, the pigment tends to migrate deeper into the reticular dermis over decades
(4) This pigment migration accounts for the degraded (faded) appearance of tattoos in older adults
Homeostatic temperature regulation occurs by two methods:
(a) Transfer of heat via sweating (evaporation)
(b) Maximizing or minimizing heat loss (radiation) via flow of blood in the dermis
High environmental temperature
Sweat production increases from the skin surface and helps lower the body temperature
(↑ evaporation)
High environmental temperature
Dermal blood vessels dilate to allow more blood flow and increase heat loss from the
body
(↑ radiation)
Low environmental temperature
Sweat production from eccrine sweat glands decrease
(↓ evaporation)
Low environmental temperature
Dermal blood vessels constrict to decrease blood flow through the skin and reduce heat loss
(↓ radiation)
produced in the epidermis that protects from microbes, abrasion, heat, water loss, and chemicals
Keratin (protein)
released by lamellar granules inhibit evaporation of water from the skin surface and prevent dehydration
Lipids (fats)
provides protection against damaging effects of UV light
Melanin (pigment)
prevent hair from drying out, are mildly bactericidal
and have acidic pH
Sebum (fat, wax esters, fatty acids)
Cutaneous Sensation
(1) Tactile sensations (exteroceptors)
(2) Thermal sensations
(3) Pain
(a) Touch (Mechanoreceptors)
(b) Pressure (baroreceptors)
(c) Vibration (Meissner Corpuscles
Tactile sensations (exteroceptors)
(a) Warmth (thermoreceptors)
b) Coolness (thermoreceptors
Thermal sensations:
(a) Impending or actual tissue damage (Nociceptors
Pain:
What activates vitamin D
Exposure of the skin to ultraviolet radiation
What is Vitamin D converted into
Vitamin D is converted to calcitriol which aids in the absorption of calcium and phosphorus
(a) The interaction between invading microbes and the reaction of the body’s immunologic response
(b) Specifically requires some form of microbe (either pathogenic or opportunistic) to invade the cellular environment
Infection
(a) The immunovascular response, without regard to the cause, to any potentially harmful stimuli (e.g., pathogens, allergens, toxins, burns, frostbite, etc.)
Inflammation
(b) Inflammation is a generic response; it is not tailored to the specific stimuli (which is why see it ALL THE TIME in medicine)
Inflammation - 5 signs:
(a) Localized Hyperthermia (due to increased blood flow)
(b) Erythema (due to dilation of blood vessels)
(c) Localized Edema (due to increased vessel permeability & extravasation of fluid)
(d) Pain (due to chemical mediators like bradykinin)
(e) Loss of function (due to all the above)
an aggregation of macrophages formed from chronic inflammation. Immune system attempts to isolate foreign substances that it cannot eliminate (pathogens, foreign objects, keratin, suture fragments).
Granulomatous inflammation (cystic)
(a) Characterized by the presence of an amorphous mass (abscess) composed of active neutrophils, cellular debris and microbes
(b) Generally caused by certain pyogenic bacteria (Staphylococcus aureus) and often forms an abscess
Suppurative Inflammation (abscesses)
(a) Inflammation occurring near epithelium that results in necrotic loss of surface tissue that exposes lower layers
(b) The subsequent excavation in the epithelium is known as an ulcer
Ulcerative inflammation (ulcers)
Derm Inflammation Patterns
(1) Granulomatous inflammation (cystic)
(2) Suppurative Inflammation (abscesses)
(3) Ulcerative inflammation (ulcers)
(1) The inevitable physiologic changes of the skin that occur with time and are influenced by genetic and hormonal factors
(2) This form of aging is not preventable and happens to everyone
Intrinsic Aging
(1) The preventable structural & functional changes of the skin that occur with exposure to:
(a) Environmental factors
(b) Lifestyle (tobacco, ETOH, illicit drugs, etc.)
(c) Social determinants
(d) Elective cosmetic surgeries
(2) Most important source of preventable extrinsic aging is ultraviolet radiation exposure
(a) Termed “photo-aging”
Extrinsic Aging
(1) Reduction of collagen fiber production enhances rate and amount of UV exposure (photodamage)
(2) Reduction of elastin fiber production decreases the elastic recovery and resilience in aged skin
(3) Abnormalities in ground substance of the connective tissue results in decreased skin hydration and characteristic elderly xerosis (dry skin)
Dermal Aging
The restoration of tissue architecture after an injury. Encompasses two separate processes:
regeneration & replacement.
(a) Damaged tissue is completely restored to its pre-injury/normal state via new growth.
(b) can happen continuously.
Example: Sloughed-off gastrointestinal epithelial cells, for example, are replaced by new cells arising from stem cells in the intestinal crypts.
Regeneration
(a) Severely damaged or non-regenerable tissue is repaired by laying down connective tissue, resulting in scarring
Example: Severe burns will require tissue replacement and will scar
Replacement
Tissue Repair Rates
(a) Most rapidly regenerating and repairing tissue and has capacity for continuous renewal
Example: The Thing in The Thing (1982) or Wolverine/Deadpool
Epithelial Tissue
Tissue Repair Rates
(a) Adequate renewal capacity; slower than epithelial tissues and prone to hyperproliferation (scarring)
Example: John Wick in every movie
Connective Tissue
Tissue Repair Rates
(a) Relatively poor capacity for renewal. Tissue does not divide rapidly enough to replace extensively damaged muscle fibers.
Example: Batman in The Dark Knight Rises
Muscular Tissue
Tissue Repair Rates
(a) Poorest capacity for renewal because it does not undergo mitosis to replace damaged neurons
Example: Jake Sully in Avatar
Nervous Tissue
Healing – Inflammation Phase
(1) Inflammatory phase (1-3 days post injury):
(a) Serves mainly to clear bacteria & debris from the wound and to prepare wound environment for repair
(2) Platelet & fibrin clot forms in the injured space, providing hemostasis and inducing both cellular and chemical inflammatory responses. Severed nerves also provide signals that increase inflammation in the injured area.
(3) Mast Cells release chemical mediators causing local capillary vasodilation, increasing permeability and augmenting local blood flow and migration of inflammatory cells to the injured area
(4) Neutrophils phagocytose cellular debris, bacteria, and foreign material, and release multiple factors that further the inflammatory reaction. After neutrophils are done, they are removed via physical sloughing or are phagocytosed themselves by macrophages.
Healing – Proliferative Phase
(1) Proliferative phase (2 to 10 days post injury):
(a) Purpose is to construct granulation tissue to fill the defect caused by the wound
(2) Fibroblasts are the major cellular agent in this phase and produce Type III collagen to provide structural integrity to the new tissue
(3) Collagen provides contractile force to minimize wound surface area during healing. Once enough extracellular matrix has been laid down most fibroblasts undergo apoptosis.
(4) Keratinocytes from wound edges migrate onto wound surface and advance across the wound, leaving proliferating keratinocytes behind until they reach the keratinocytes on opposite wound edge
Healing – Early Remodeling Phase
(1) 2–3 weeks post-injury: tissue defects have been replaced with granulation tissue & covered by new epithelial cells
(2) Wound tissue now consists of disorganized collagen and extracellular matrix proteins without dermal appendages (hair follicles/sweat glands) and is covered with epithelium
(3) Surface of the wound contracts, causing base of the wound to be wider than the surface
(4) Fibroblasts, macrophages, and endothelial cells in wound space begin to apoptosis or exit wound
Healing – Late Remodeling Phase
(1) Remodeling Phase (months to > 1 year):
(2) The type III collagen laid down by the fibroblasts are replaced with type I collagen and collagen fibrils become more organized
(3) As collagen rearranges, the tensile strength of the wound increases from 20% at 3 weeks after injury, to 70–80% at 6 weeks, but never reaches the full strength of uninjured tissue
(4) Over time, collagen fiber rearrangement makes the scar become less thick & firm
(5) The initial capillaries formed in the inflammatory phase regress and the scar becomes and less erythematous
(1) Relies on dermal edges that are close together and easily approximated
Healing by Primary Intention
Healing by Primary Intention
Pros
Cons
(2) Pros:
(a) Most often results in a complete return to function with minimal scarring & loss of skin appendages
(b) Sutures, staples, and dermal adhesive are readily available to the IDC
(3) Cons:
(a) Requires relatively clean wounds without major avulsion or asymmetric/jagged edges
(b) Easily mismanaged by providers who lack experience and proper technique
(c) Potential for scarring & poor cosmetic outcome due to patient non-compliance
Examples: Sutures, staples, dermal adhesive
(1) Relies on formation of granulation tissue to fill the space between the wound opening or edges
Healing by Secondary Intention
Healing by Secondary Intention
Pros
Cons
(2) Pros:
(a) Decreases chance of wound infection by allowing exudate drainage from the wound
(b) Closure of choice when dealing with a large wound made by infection
(3) Cons:
(a) Wounds take much longer to heal
(b) Greater likelihood of scar formation because edges are not approximated
(c) Wounds must be regularly examined and re evaluated to ensure proper care
