Lab 1: Histology and Integumentary System Flashcards
define histology
the study of tissues
define tissues
a group a similarly structured cells that work together to accomplish a specific function
what are the four major tissue categories
- epithelial
- connective
- muscle
- nervous
how are specimens for histology prepared
- fixed/preserved
- thinly sectioned
- stained to improve contrast
what is the difference between acid stains and basic stains
- acid stains have negatively charged dyes
- basic stains have positively charged dyes
what do dyes bind to
oppositely charged macromolecules
define artifact
- a minor distortion in sectioned tissues that is only present due to the many steps needed to produce a histology slide
- should not be confused with the actual structure of preserved tissue
what does epithelial tissue do
- lines and covers organs, as well as their internal passageways
- creates boundaries between different environments
- forms glands
what are the strong intercellular connections between epithelial cells formed by
- tight junctions
- desmosomes
describe tight junctions
- connections between adjacent cells
- prevents fluid from moving between the cells
describe desmosomes
- connections between adjacent cells
- contains proteins
- allows cells to mechanically hold on to each other, providing mutual reinforcement
what are the functions of epithelia
- filtration
- absorption
- protection
- secretion
- excretion
- sensory reception
define the free/apical surface of epithelium
surface where cells are exposed to external environment or internal passageway/cavity
how do cells on the free/apical surface of epithelium obtain nutrients
diffusion of substances from connective tissue underlying the epithelia
define the basal lamina of epithelium
- where epithelium is attached to the body
- located between the epithelium and the connective tissue layer
what is the composition of basal lamina of epithilium
- glycoprotein secretions from the epithelial cells
- collagen fibers
what is the function of the basal lamina
- filter at the base of the epithelium
- forms a scaffold for wound repair
how are epithelia named
- shape
- number of cell layers
define simple epithelium
epithelium with only one layer of epithelial cells
what are the functions of simple epithelia
- diffusion
- absorption
- filtration
- secretion
what is the function of goblet cells
protect epithelia at the free surface by secreting mucus that coats the cell
describe the two different attachments on epithelial cells on the apical surface
- microvilli: increase surface area for absorption
- cilia: motile hair-like projections that sweep substances across the apical surface
define stratified epithelia
epithelium with more than one layer of epithelial cells
where is stratified epithelia found
- areas exposed to abrasion and friction
- body surface, upper digestive tract
what is the main function of stratified epithelia
protection
when stratified epithelium contains more than one type/shape of epithelial cell, how do you determine the classification of the tissue
the type of epithelial cell at the free surface determines the classification of the tissue
describe how stratified epithelia regenerates
regenerates from basal cells that divide and then move out to replace older cells near the apical border
what is the most common stratified epithelium
stratified squamous epithelium
what happens to cells on the apical surface of stratified epithelium and why
they often atrophy and flatten because they are furthest from the blood supply
how many layers thick is stratified cuboidal epithelium typically
two cells thick
where is stratified cuboidal epithelium found
- ducts of sweat glands
- mammary glands
where is stratified columnar epithelium found
- parts of the male urethra
- the pharynx
- lining of some glandular ducts
describe a squamous-shaped cell
- flattened shape
- nucleus appears flattened
describe a cuboidal-shaped cell
- cube shaped
- round nucleus
describe a columnar-shaped cell
- rectangle shaped, like a column
- oblong or round nucleus
what are the 6 characteristics that distinguish epithelial tissue from other tissue types
- regeneration
- polarity
- cellularity and specialized contacts
- supported by connective tissue
- avascularity
- innervated
why is cellular regeneration important for epithelial cells
many epithelia are subjected to friction or exposed to hostile/caustic substances
describe the concept of polarity in epithelial tissue
- there are differences in structure and function between the apical and basal surface of epithelia
- apical surfaces also differ: microvilli, smooth, cilia
describe a brush border
- microvilli on the apical surface of epithelial tissue are so dense they appear fuzzy
- often seen in secretory or absorbing tissues
how are epithelial cells attached to connective tissue
basement membrane
describe the basement membrane
- attaches epithelial tissue to connective tissue
- helps epithelia resist tearing and stretching
- reinforces structural integrity
- creates a boundary
- made up of basal lamina and reticular lamina
describe reticular lamina
- made of collagen fibers
- secreted by connective tissue
- part of the basement membrane
describe the significance of the basement membrane in cancer
cancers of the epithelial tissue cannot become metastatic until they develop a mechanism to break through the basement membrane
what is the only type of epithelia that is vascular
glandular epithelial tissue
define innervated
supplied by nerve fibers for regulation
what tissue has the highest regeneration capacity and what has the lowest
- highest regeneration: epithelial tissue
- lowest regeneration: nervous tissue
describe simple squamous epithelium
- thin and often permeable
- single layer of flattened cells with disc shaped nuclei and sparse cytoplasm
what is the function of simple squamous epithelium
- filtration and diffusion
- not protective
- secretes lubricating substances in serosae (tissue lining of a body cavity or outer lining of an organ)
locations of simple squamous epithelia
- kidney glomeruli
- air sacs of lungs
- lining of heart, blood vessels, and lymphatic vessels
- lining of ventral body cavity
what are the two specific types of simple squamous epithelia
- endothelium
- mesothelium
describe endothelium
- simple squamous epithelia
- provides slick and friction-reducing lining in hollow organs that transmit body fluids (lymph, blood)
describe mesothelium
- simple squamous epithelia
- found in serous membranes lining the ventral body cavity and covering its organs
describe simple cuboidal epithelium
- single layer of cube-like cells
- large, spherical central nuclei
what is the function of simple cuboidal epithelium
secretion and absorption
locations of simple cuboidal epithelium
- kidney tubules
- ducts and secretory portions of small glands
- ovary surface
describe simple columnar epithelium
- single layer of tall cells
- round to oval nuclei
- some cells have cilia
- layer may contain mucus-secreting unicellular glands (goblet cells)
function of simple columnar epithelium
- absorption
- secretion of mucus, enzymes, and other substances
- ciliated type propels mucus or reproductive cells by ciliary action
locations of simple columnar epithelium
- non-ciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands
- ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus
describe keratinized epithelial cells
cells manufacture the protein keratin which toughens the cells as they die creating a dry protective barrier against abrasion, chemical exposure, and friction
describe stratified squamous epitheium
- thick membrane composed of several layers
- basal cells are cuboidal or columnar and metabolically active white surface cells are squamous
- surface cells in the keratinized type are full of keratin and dead
function of stratified squamous epithelium
protect underlying tissues in areas subjected to abrasion
locations of stratified squamous epithelium
- keratinized: epidermis of the skin
- non-keratinized: moist linings of the esophagus, mouth, and vagina
describe pseudostratified ciliated columnar epithelium
- single layer of cells of differing heights
- some cells don’t reach the free surface, but all cells touch the basal lamina
- nuclei seen at different levels
- may contain mucus-secreting cells (goblet cells)
- may bear cilia
function of pseudostratified ciliated columnar epithelium
- secretion, particularly of mucus
- propulsion of mucus by ciliary action
locations of pseudostratified ciliated columnar epithelium
- non-ciliated: male’s sperm-carrying ducts and ducts of large glands
- ciliated: lining nasal cavity, trachea, and bronchi
describe transitional epithelium
- resembles both stratified squamous and stratified cuboidal
- basal cells are cuboidal or columnar, surface cells dome-shaped or squamous-like
- not all cells touch the basal lamina
function of transitional epithelium
stretches readily and permits distension of certain hollow organs
locations of transitional epithelium
- organs that must stretch and shrink
- lines uterus, urinary bladder, and part of the urethra
what are the main functions of connective tissue
- provides the body with structural support and means of joining structural components to one another
- protection
- storing energy reserves
- insulating the body
- transporting substances throughout the body
what creates all connective tissues
mesenchyme, an embryonic tissue
describe the general composition of connective tissue
- mostly non-cellular
- cells sparsely spread throughout extracellular matrix
describe the general composition of the extracellular matrix in connective tissue
protein fibers and a ground substance secreted by cells in connective tissue
describe collagen fibers in the ground substance of the extracellular matrix of connective tissue
- strongest of the fibers
- made of the protein collagen
- made of many cross-linked fibrils
describe elastic fibers in the ground substance of the extracellular matrix of connective tissue
- made of the protein elastin
- forms in branching network int he extracellular matrix to provide strength and recoil
describe reticular fibers in the ground substance of the extracellular matrix of connective tissue
- short and fine
- made of the protein collagen
- form fuzzy nets with more give than that of collagen fibers
- less secreted as we age, leading to brittle bones and wrinkly skin
what are the three groups of connective tissue
- connective tissue proper
- fluid connective tissue
- supporting connective tissue
describe general characteristics of connective tissue proper
- thick liquid matrix
- variety of cell types
- divided into two groups: loose and dense
what do fibroblasts do in connective tissue proper
stationary cells that secrete proteins to form fibers
what do macrophages do in connective tissue proper
- patrol tissues and are mobilized during an infection or injury
- migrate to the site of the disturbance and phagocytize damaged tissue cells and microbes
what do mast cells do in connective tissue proper
- detect foreign microorganisms and initiate immune response
- release histamine that causes inflammatory response
- secrete enzymes such as heparin and proteases
what do adipocytes do in connective tissue proper
fat cells containing vacuoles for lipid storage
what are the three groups of loose connective tissues
- areolar
- adipose
- reticular
what are the two types of fibers that make up dense connective tissue
- protein fibers assembled into thick bundles of collagen
- elastic fibers with widely scattered cells
what are the two types of dense connective tissue
- dense regular
- dense irregular
describe the fiber arrangement in dense regular vs irregular connective tissue
- regular: protein fibers arranged in parallel bands
- irregular: fibers interwoven running in many directions
where is dense irregular connective tissue found
- where tension is exerted from many different directions
- capsules of some organs and joints
- dermis of the skin
- submucosa of digestive tract
describe the two types of fluid connective tissue
- blood: erythrocytes and leukocytes
- lymph
what are the two types of supporting connective tissue
- bone
- cartilage
what is the solid matrix of bone composed of
calcium phosphate salt, aka hydroxyapatite
what are the general functions of bone
- support and protect the body
- provides cavities for synthesis of blood cells and storing fat
why is bone more rigid than cartilage
bone has more collagen fibers and a matrix filled with hydroxyapatite
which is highly vascularized and innervated: bone or cartilage
bone
describe cartilage
- rubbery
- avascular
- non-innervated
- gelatinous matrix
- fibers for structural support
- can withstand both compression and tension because it is tough but flexible
define perichondrium
- membrane surrounding all supporting connective tissue in cartilage
- produces chondroblasts
what do chondroblasts do
- secrete fibers and the ground substance of cartilage matrix
how does cartilage receive nutrients
diffusion from the perichondrium
describe how chondroblasts become chondrocytes
- chondroblasts are produced by the perichondrium
- chondroblasts become trapped in small spaces of the matrix called lacunae
- then become chondrocytes that maintain mature tissue
what are the three types of cartilage
- hyaline
- elastic
- fibrocartilage
describe areolar tissue
- loose connective tissue
- gel-like matrix with all three fiber types
- flexible
- includes fibroblasts, macrophages, mast cells, and some white blood cells
- collagen and elastic fibers are clearly visible in the matrix
functions of areolar tissue
- fills spaces between structures for support and protection
- wraps and cushions organs
- macrophages phagocytize bacteria
- mast cells cause inflammation
- holds and conveys tissue fluid
locations of areolar tissue
widely distributed under the skin
describe adipose tissue
- loose connective tissue
- similar matrix to areolar tissue
- closely packed adipocytes
- nucleus pushed to the side by large fat vacuole
functions of adipose tissue
- reserve food fuel
- insulates against heat loss
- supports and protects organs
locations of adipose tissue
- under the skin in subcutaneous tissue
- around kidneys and eyeballs
- within abdomen
- in breasts
describe reticular tissue
- loose connective tissue
- forms internal supporting framework for soft organs
- composed of network of reticular fibers interspersed with reticulocytes
functions of reticular tissue
fibers form soft internal skeleton that supports other cell types including white blood cells, mast cells, and macrophages
locations of reticular tissue
lymphoid organs (lymph nodes, bone marrow, spleen)
describe dense regular connective tissue
- consists mostly of collagen with some elastic fibers organized into parallel thick bands
- fibroblasts widely interspersed
- poorly vascularized
functions of dense regular connective tissue
- attaches muscles to bones or muscles
- attaches bone to bone
- withstands great tensile stress when pulling force is applied in one direction
locations of dense regular connective tissue
- tendons
- most ligaments
- aponeuroses
define fascia
- flat layers of dense regular connective tissue
- protect and isolate muscles from surrounding structures and allow muscle movement
describe dense regular elastic tissue
dense regular connective tissue with high proportion of elastic fibers
functions of dense regular elastic tissue
- allows recoil of tissue following stretching
- maintains pulsatile flow of blood throw arteries
- aids passive recoil of lungs following respiration
locations of dense regular elastic tissue
- walls of large arteries
- ligaments associated with the vertebral column
- walls of bronchial tubes
describe blood
composed mostly of formed elements (erythrocytes, leukocytes, thrombocytes) suspended in plasma
functions of blood
transport of respiratory gases, nutrients, wastes, and other substances
location of blood
contained within blood vessels
what are the specific functions of the three formed elements in blood
- erythrocytes: transport blood gases
- leukocytes: protect the body from infection
- thrombocytes: form a plug to reduce bleeding
what is the most common cartilage in the body
hyaline cartilage
what makes hyaline cartilage different from other cartilages
- the apparent lack of fibers in the matrix
- there are elastic and collagen fibers but they do not stain
describe hyaline cartilage
- amorphous but firm matrix
- collagen fibers form imperceptible network
- chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae
function of hyaline cartilage
- springy absorption of compression at joints
- supports and reinforces
- resilient cushioning properties
- resists compressive stress
location of hyaline cartilage
- embryonic skeleton
- ends of long bones in joint cavities
- costal cartilages of the ribs
- cartilages of the nose, trachea, and larynx
describe elastic cartilage
- similar to hyaline cartilage
- more elastic fibers in matrix that are visible
function of elastic cartilage
maintains shape of a structure while allowing great flexibility
location of elastic cartilage
- supports external ear (pinna)
- epiglottis
describe fibrocartilage
- matrix similar but less firm than that in hyaline cartilage
- thick collagen fibers predominate and visible
function of fibrocartilage
- tensile strength
- cushions joints by absorbing compressive shock
- limits bone movement
location of fibrocartilage
- intervertebral discs
- pubis symphysis
- discs of knee joint
describe skeletal muscle tissue
- composed of long cells called muscle fibers which are composed of myoblasts
- multinucleate cells
- striated due to organization of intercontractile proteins called myofilaments (actin and myosin)
function of skeletal muscle tissue
- voluntary movement
- locomotion
- manipulation in the environment
- facial expressions
location of skeletal muscle tissue
- in skeletal muscles attached to bones
- occasionally in muscles attached to skin
describe cardiac muscle tissue
- branching
- striated
- uninucleate cells
- cells connect at specialized junctions called intercalated discs which are desmosome rich
function of cardiac muscle tissue
- involuntary movement
- propels blood into circulation as it contracts
location of cardiac muscle tissue
the walls of the heart
describe smooth muscle tissue
- spindle-shaped cells with central nuclei
- no striations
- cells arranged closely to form sheets
function of smooth muscle tissue
- involuntary movement
- propels substances or objects along internal passageways
location of smooth muscle tissue
mostly in the walls of hollow organs
what are the two types of cells that make up the nervous system
- neurons
- glial cells
define nerve/neural tissue
collective of neurons and glial cells
describe the distinct regions of a typical neuron
- central nucleus surrounded by the cell body/soma that contains most of the organelles
- dendrites radiate out from the soma and receive signals from other cells which they send to the soma
- axon connects to the soma and sends signals to other cells
describe nervous tissue
- neurons are branching cells
- cell processes can be long
- other non-irritable supporting cells around the neuron
function of nervous tissue
transmit electrical signals from sensory receptors and to effectors (muscles and glands)
location of nervous tissue
- brain
- spinal cord
- nerves
define periosteum
- membrane surrounding bone supporting tissue
- contains osteoblasts for bone growth and repair
describe the function of osteoblasts
- bone growth and repair
- secrete organic components of the matrix
- become osteocytes when in the lacunae
what is the bulk of compact bone composed of
repeating structural units called osteons
what are osteons composed of
rings of concentric lamellae surrounding a central (haversian) canal that contains blood vessels and nerves
define canaliculi
- small channels in the lamellae that provide passageways through the solid matrix for diffusion of nutrients and wastes with the blood
- radiate from the central canal of the osteon
what are the main functions of bones
- provide structural support for the body
- provide point of attachment to skeletal muscles
- protect internal organs
what cells help calcium in bones to be stored and released as needed
- osteoblasts: constantly resynthesizing bone
- osteoclasts: constantly reabsorbing bone
what are the two ways that bone ossifies
- intramembranous bone
- endochondral bone
which bones are intramembranous bones
- cranial bones
- the clavicle
what do intramembranous bones develop from
fibrous membranes and endochondral bone
what does endochondral bone develop from
hyaline cartilage
describe the purpose and location of a Volkmann’s canal/perforating canal
- carries nerves, blood vessels, and lymphatic vessels from the periosteum
- perpendicular to the osteon
- connects with the central/Haversian canal
what is the difference between concentric lamellae and interstitial lamellae
- concentric lamellae makes up each osteon
- interstitial lamellae fills the space between osteons
what is included in the integumentary system
- the skin
- sweat and oil glands
- hair
- nails
what’s the largest organ in the body
the skin
what are the functions of the integumentary system
- protective barrier that is flexible but resistant to everyday abrasions and indiscriminate water loss
- regulates body temperature
- houses sensory receptors
- ensures water homeostasis
- protects the body from the environment
- manufactures vitamin D3
what are the two main tissue layers of the integument
- superficial and avascular epidermis
- deep and vascularized dermis
what type of tissue does the epidermis consist of
keratinized stratified squamous epithelium
what cell type are most cells in the epidermis
keratinocytes that produce keratin
where are keratinocytes produced
produced by the basal layer of the epidermis and migrate out
what is the lifespan of a keratinocyte
25-45 days
what determines whether skin is thick or thin
the thickness of the epidermis
what are the five layers of the epidermis starting from the apical layer
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
describe the stratum corneum
- horny layer
- most superficial layer of epidermis
- 20-30 layers of dead squamous anucleate cells
- 2/3 of epidermis thickness
- contains keratin
what are the functions of the stratum corneum
- keratin and thick plasma membranes protects the skin against abrasions
- glycolipids between cells waterproofs skin
describe the stratum lucidem
- clear layer
- just deep to the stratum corneum layer of the epidermis
- thin and transparent layer of cells
- found in thick skin areas (palm of hand, sole of feet)
what is the function of the stratum lucidem
protect the underlying strata in areas subject to abrasion
describe tonofilaments including their location
- parallel arrays of filaments created when keratohyalin granules cling to the keratin filaments within the dying cells
- located in the stratum corneum and stratum lucidem of the epidermis
describe the stratum granulosum
- granular layer
- deep to the stratum corneum (or stratum lucidem if present)
- 4 to 6 layers of darks cells that synthesize keratohyaline and lamellar granules
- where keratinization occurs
what is the purpose of lamellar granules in the stratum granulosum
- released into the extracellular space
- contain a water-resistant glycolipid
what is the purpose of keratinization in the stratum granulosum
- increase durability
- reduce water loss from the integument
describe the stratum spinosum
- prickly layer
- deep to the strum granulosum in the epidermis
- 5 to 7 cells that form cell attachments via desmosomes
- keratinocytes in this layer appear to have spines (prickly appearance) but this is an artifact of preparation of cells
- melanin granules and dendritic cells
why do keratinocytes in the stratum spinosum appear to have spines or a prickly appearance
artifact of preparation of cells
describe the stratum basale
- basal layer
- deepest epidermal layer
- attached to the dermis
- single layer of stem cells constantly undergoing mitosis
- melanocytes producing melanin
what happens to the daughter cells produced by mitosis in the stratum basale of the epidermis
- one daughter cell is pushed into the stratum spinosum
- other daughter cell stays in the stratum basale
describe what melanocytes and melanin do (life cycle of melanin)
- found in the stratum basale of the epidermis
- produce the pigment melanin which is packaged into melanosomes and secreted from the tips of the melanocyte
- melanin is taken up by keratinocytes and sits on the superficial sun exposed side of the nucleus to protect DNA from sun exposure
describe the dermis
- layer of irregularly arranged flexible and strong connective tissue
- supports and nourishes the epidermis
- supply of nerve fibers, blood vessels, and lymphatic vessels
what are the two layers of the dermis
- papillary layer
- reticular layer
describe the papillary layer
- superficial layer of the dermis
- consists of areolar tissue that contains collagen and elastic fibers
- folds called dermal papillae
- houses phagocytes
describe dermal papillae
- folds in the papillary layer of the dermis
- form dermal ridges that make fingerprints
- often contain Meissner’s corpuscles, free nerve endings, or capillary loops
describe Meissner’s corpuscles
- found in the dermal papillae of the papillary layer of the dermis
- touch receptors
describe the reticular layer
- deep layer of the dermis
- thick layer containing thick collagen fibers in dense irregular connective tissue
- pockets of adipose cells
- where hair follicles and glands originate
what lays between the dermis and hypodermis
cutaneous plexus of blood vessels
what is excreted in sweat
- water
- small amounts of sodium chloride, ammonia, urea, and uric acid
define exteroceptors
- found in the skin
- respond to stimuli from outside the body
what are the three major types of hair found in humans
- terminal
- vellus
- intermediate
define terminal hairs
- thick, coarse, heavy, dark
- on the scalp, eyebrows, and eyelashes
define vellus hairs
- lightly pigmented
- distributed over much of the skin as fine peach fuzz
define intermediate hairs
the hair on the arms and legs
what is the deepest part of the hair root called
hair bulb
what is contained in the hair papilla within the hair bulb
- nerves
- blood vessels
- the beginning of the hair matrix
define hair matrix
the living and proliferative part of the hair
what is the hair follicle wall (not the hair shaft) made of
- outermost peripheral connective tissue sheath
- a glassy membrane of thickened basal lamina
- innermost epithelial root sheath (divided into thick and thin layers)
what are the three parts of the hair shaft
- outermost cuticle containing a single layer of overlapping cells to separate adjacent cells so the hairs do not mat and hard keratin
- outer cortex containing flattened cells filled with hard keratin
- inner medulla containing soft keratin and big cells
describe what shape of the hair shaft will make hair kinky, wavy, and straight
- kinky: flat hair shaft
- wavy: oval hair shaft
- straight: round
when is the hair medulla absent
in fine hairs
what extra pigment is in red hair
pheomelanin
describe the arrector pili muscle
- smooth muscle
- attached to each hair follicle
- contract when cold or experiencing heightened emotional state (goose bumps)
- move sebum from hair follicles to skin surface for lubrication when they contract
describe exocrine glands
- secrete substances onto a body surface or into a body cavity
- do not release hormones into the circulation
- produce saliva, oil, sweat, mucus, bile, digestive enzymes from the pancreas
how to unicellular and multicellular exocrine glands differ
- unicellular: release secretions by exocytosis directly onto the epithelial surface
- multicellular: secretion passes through a duct on its way to the surface
what are the three types of exocrine gland cells
- merocrine
- apocrine
- holocrine
describe merocrine cells/glands
- in exocrine glands
- secretions exerted via exocytosis from secretory cells onto an epithelial-walled ducts or ducts then onto body surface
- ex: salivary gland
describe apocrine cells/glands
- in exocrine glands
- secretions bud off through the plasma membrane producing membrane-bound vesicles in the lumen
- ex: mammary gland
describe holocrine cells/glands
- in exocrine glands
- secretions produced in the cytoplasm of the cell and released by the rupture of the plasma membrane
- destroys the cell and results in secretion of the product into the lumen
- ex: sebaceous gland
describe apocrine sweat glands
- larger and in less locations (axillary and public) than eccrine sweat glands
- activated by sex steroids during puberty
- contain lipids and proteins not found in eccrine sweat glands, may contain pheromones
describe eccrine sweat glands
- smaller and in more locations than apocrine sweat glands
- exist throughout the dermis
- stop bacterial growth by creating the acid mantle
- vital for thermoregulation