WEEK 4: Tissues and Bones Flashcards
What are tissues
- collections of specialized cells and cell products that perform specific functions
- tissues in combination form organs, such as the heart or liver
What is histology
Study of tissues
What are 4 types of tissues
- Epithelial
- Connective
- Muscle
- Nervous
What is Epithelial tissue and examples
- covers exposed surfaces
- lines internal passageways
- forms glands
includes:
->epithelia: layers of cells covering internal or external surfaces
->glands: structures that produce fluid secretions
What is the 4 functions of epithelial tissue
- Provide physical protection
- Control permeability
-Provide sensation - Produce specialized secretions
The 5 characterisitcs of epithelial tissue
- polarity (apical and basal surfaces)
-> On apical surface: microvilli increase absorption or secretion
cilia on a ciliated epithelium move fluids - cellularity (cell junctions)
- attachment (basement membrane)
- avascularity (avascular)
- regeneration
The 3 specilisations of epithelial cells
- Move fluids over the epithelium (protection)
-Move fluids through the epithelium (permeability) - Produce secretions (protection and messaging)
What 3 things maintain the integirty of epithelia
- Intercellular connections
- Attachment to the basement membrane
-Epithelial maintenance and repair
What do intercellular connections do
- support and communication
-> cell adhesion molecules (CAMS)
-> transmembrane proteins - proteoglycans act as intercellular cement
-> contain glycosaminoglycans such as hyaluronan (hyaluronic acid)
What are cell functions and the 3 typrs
- Form bonds with other cells or extracellular material
- Gap junctions
- Tight junctions
- Desmosomes
What are gap junctions?
- allow rapid communication
- cells held together by interlocking transmembrane proteins (connexons)
- allow small molecules & ions to pass(diffusion)
- coordinate contractions in heart muscle
What are Tight junctions
- between two plasma membranes
- adhesion belt attaches to terminal web
- prevent passage of water and solutes
- keep enzymes, acids, and wastes in lumen of digestive tract
How are desosomes formed, and the 2 types and their functions
- CAMS and proteoglycans link opposing plasma membranes
- spot desmosomes
->tie cells together
->allow bending and twisting - hemidesmosomes
-> attach cells to the basement membrane
The 2 lamina attached to the basement membrane
- basal lamina
->closest to the epithelium - reticular lamina
->deeper portion of basement membrane provides strength
How is the epithelila maintained and repaired
- epithelial cells replaced by continual division of stem cells
- located near basement membrane
What are the classifications of epithelia based on? (2)
Shape and layers
The 3 classifications of epithelia based on shape?
- squamous—thin and flat
- cuboidal—square shaped
- columnar—tall, slender rectangles
The 2 classifications of epithelia based on layers?
- simple epithelium—single layer of cells
- stratified epithelium—several layers of cells
What are the 2 types of squamous epithelia
simple squamous epithelia
Stratified squamous epithelia
What is simple squamous epithelia
- reduces friction
- performs absorption and secretion
- controls vessel permeability
- mesothelium
- > lines body cavities
- endothelium
- > forms inner lining of heart and blood vessels, portions of kidney tubules
What is Stratified squamous epithelia
- protect against mechanical stresses
- keratin adds strength and water resistance
- found in surface of skin, lining of mouth, throat, esophagus, rectum
What are the 2 types of cuboidal epithelia
- simple cuboidal epithelia
- Stratified cuboidal epithelia
What is simple cuboidal epithelia, where is it found in and funcitons
- secretion and absorption
- ## found in glands and portions of kidney tubules
What is Stratified cuboidal epithelia, where is it found in and functions
- relatively rare
- ducts of sweat glands and mammary glands
- protects, secretion and absroption
What is transitional epithelia, function and found in
- tolerate repeated cycles of stretching without damage
- appearance changes as stretching occurs
- found in urinary bladder
What are the 3 types of collumnar epithelia
- simple columnar epithelia
- pseudostratified columnar epithelia
- stratified columnar epithelia
Functions and where its found: simple columnar epithelia
->absorption and secretion, protection
->found in lining of stomach, small intestine, large intestine, gall bladders, uterine tubes
Functions and where its found: pseudostratified columnar epithelia
->typically have cilia
->protein, secretion, move mucus w cillia
->found in lining of nasal cavity, trachea, bronchi
Functions and where its found: stratified columnar epithelia
->relatively rare
->provide protection in pharynx, anus, urethra, epiglottis, mammary glands
What are glandular epithelia, and 2 types of glands=functions
- glands are collections of epithelial cells that produce secretions
- Endocrine glands: release hormones that enter bloodstream
->no ducts - Exocrine glands: produce exocrine secretions
-> discharge secretions through ducts onto epithelial surfaces
What 2 types of glands make up gland structure
unicellular glands
multicellular glands
What is unicellular glands, found in, functions
- goblet cells are unicellular exocrine glands
->found in epithelia of intestines
->secrete mucin, which mixes with water to form mucus
What 3 things are multicellular exocrine glands classified by
- Structure of the duct
- Shape of secretory portion of the gland
- Relationship between ducts and glandular areas
What 2 things can mutliceullular gands duct structure be classified by
- simple (undivided)
- compound (divided)
What 2 things can mutliceullular gands shape of secretor portion of gland be classified by
- tubular (tube shaped)
- alveolar or acinar (blind pockets)
What 1 thing can mutliceullular glands relationships between ducts+glandular areas be classified by
branched (several secretory areas sharing one duct)
What are the 5 simple exocrine glands, example for each
- Simple tubular
- eg intestinal glands - simple coiled subular
- eg merocrine sweat glands - simple branched tubular
e.g gastric/mucous glands - simple alveolar
eg. not found in adults - simple branched alveolar
eg. sebaceous glands
What are the 3 compound glands, example for each
- compound tubular
e.g mucous glands, testes - compound alveolar
e.g mammary glands - compound tubulo-alveolar
e.g salivary glands, glands of respiratory passages, pancreas
What the 3 methods of secretion, released by, example
- Merocrine - released by secretory vesicles (exocytosis)
->example: merocrine sweat glands, salivary glands - Apocrine - released by shedding cytoplasm
->example: mammary glands - Holocrine - released by cells bursting, killing gland cells
gland cells replaced by stem cells
->example: sebaceous glands on hair follicles
3 Types of secretions produced by exocrine glands
-serous glands=watery secretions
- mucous glands=secrete mucins
- mixed exocrine glands= both serous and mucous
What are the 3 components of connective tissues
- Specialized cells
- Extracellular protein fibers
- Fluid called ground substance
What does the matrix consist of
- extracellular components of connective tissue (fibers and ground substance)
- majority of tissue volume
- determines specialized function
What are the 6 functions of connective tissue
- establishing a structural framework for the body
- transporting fluids and dissolved materials
- protecting delicate organs
- supporting, surrounding & interconnecting other types of tissue
- storing energy reserves, especially triglycerides
- defending the body from invading microorganisms
What are the 3 categories of connective tissue and their function
- Connective tissue proper
->connect and protect - Fluid connective tissues [blood and lymph]
->transport
- Supporting connective tissues
->structural strength
What is loose connective tissue + example
more ground substance, fewer fibers
- fill spaces between organs, cushion cells, and support epithelia
example: fat (adipose tissue)
What is dense connective tissue + example
more fibers, less ground substance
- also called collagenous tissues
contain many collagen fibers
example: tendons
What are the 9 cells of connective tissue proper
- Fibroblasts
- Fibrocytes
- Adipocytes
- Mesenchymal cells
- Melanocytes
- Macrophages
- Mast cells
- Lymphocytes
- Microphages
What are fibroblasts and what do they secrete
the most abundant cell type
- secrete proteins and hyaluronan (cellular cement)
What are fibrocytes and function
second most abundant type - maintain connective tissue fibers
What are adipocytes
fat cells - each cell stores a single, large fat droplet
What are Mesenchymal cells function
stem cells that respond to injury or infection
What are melanocytes function
synthesize and store the brown pigment melanin
What are macrophages and function
- large phagocytic cells of the immune system
- engulf pathogens and damaged cells
- fixed macrophages stay in tissue
- free macrophages migrate
What are mast cells and function
- stimulate inflammation after injury or infection
-> release histamine and heparin - basophils are leukocytes that also contain histamine and heparin
What are 3 connective tissue fibres
- Collagen fibers
- Reticular fibers
- Elastic fibers
What are the 5 characterisitcs collagen fibers
- most common fibers in connective tissue proper
- long, straight, and unbranched
- strong and flexible
- resist force in one direction
- abundant in tendons and ligaments
What are the 3 characterisitcs reticular fibers and example
- form a network of interwoven fibers (stroma)
- strong and flexible - resist forces in many directions
- stabilize functional cells (parenchyma) and structures
- example: sheaths around organs
What are the 2 characterisitcs elastic fibers and example
- contain elastin
- branched and wavy - return to original length after stretching
- example: elastic ligaments of vertebrae
What is a ground substance and their function
- is clear, colorless, and viscous
- fills spaces between cells and slows pathogen movement
What are the 3 types of loose connective tissue in adults
Areolar tissue
Adipose tissue
Reticular tissue
What are areolar tissue, functions and example
- least specialized, open framework, viscous ground substanceelastic fibers
- holds capillary beds
- cushions organs
- provides support support/permits independent movement
- phagocytic cells defend
- example: under skin (subcutaneous layer)
What is adipose tissue, found in, functions
- contains many adipocytes (fat cells)
- cells do not divide
- expand to store fat & shrink as fats are released
- found deep in skin, padding around eyes/kidneys
- provides padding+cushions shocks
- insulates+stores energy
What is reticular tissue, found in, functions
- provides supporting framework
- forms a complex, three-dimensional stroma
- support functional cells of organs
- found in liver, kidney, spleen, lymph nodes, bone marrow
What are the three types of dense connective tissue
dense regular
dense irregular
elastic
What is dense regular tissue, found in, functions
- tightly packed, parallel collagen fibers
- tendons attach muscles to bone
- ligaments connect one bone to another
- aponeuroses are tendinous sheets that attach a broad, flat muscle to another structure
- found between tendons, liagament, aponeruoses
- provides firm attachment
- conduts pull of muscle
- reduces friction between muscles
- stabilises position of bone
What is dense irregular tissue, found in, functions
- interwoven network of collagen fibers
->provides strength to dermis
-> helps prevent overexapnsion of organs(univary bladder)
->forms sheath around cartilages (perichondrium) and bones (periosteum)
->forms capsules around some organs (e.g., liver, kidneys, and spleen)
What is elastic tissue, found in, functions
- made of elastic fibers
- stabilises position of vertebrae/penis
- cushions shocks
- permits expansion+contraction of organs
- example: elastic ligaments of spinal vertebrae
What 3 things does the cardiovasucalr system consist of
- a pump (the heart)
- series of conducting hoses (blood vessels)
- contains the fluid connective tissue blood
What is blood
- specialized connective tissue
- contains cells suspended in a fluid matrix
What is the 5 functions of blood
- transporting dissolved gases, nutrients, hormones, and metabolic wastes
- regulating pH, ion composition of interstitial fluids
- restricting fluid losses at injury sites
- defending against toxins and pathogens
- stabilizing body temperature
What is blood components
- Plasma :fluid
-Formed elements : cells and cell fragments
What is fractionation
process of separating whole blood into plasma and formed elements
What is plasma
- makes up ± 55% of blood volume
- more than 90% of plasma is water
also contains dissolved plasma proteins & other solutes - similar in composition to interstitial fluid
-> because water, ions, and small solutes are exchanged across capillary walls
The 3 types of formed elements found in blood
- Red blood cells
- White blood cells
- Cell fragments (platelets)
What is hemopoiesis
- Process of producing formed elements
What are platelets
small, membrane bound cell fragments that contain enzymes + other substances important for clotting
What are red blood cells
- also called erythrocytes
- make up 99.9% of formed elements
- contain hemoglobin
->red pigment that gives whole blood its color
->binds and transports oxygen and carbon dioxide
Describe structure of rbcs
- small, highly specialized cells
- biconcave discs
-> thin central region and thicker outer margin
What are mature rbcs
- anucleate (lack nuclei)
- lack mitochondria and ribosomes
- unable to divide, synthesize proteins, or repair damage
- live ± 120 days
What are surface antigens
- substances on plasma membranes that identify cells to immune system
- normal cells are ignored and foreign cells are attacked
What is blood type
-determined by presence or absence of surface antigens on RBCs: A, B, and Rh (or D)
What are the 4 blood types
- Type A (surface antigen A)
- Type B (surface antigen B)
- Type AB (antigens A and B)
- Type O (neither A nor B)
What is Rh blood group
- based on presence or absence of Rh antigen
- Rh positive (Rh+)
->Rh surface antigen is present (e.g., Type O+) - Rh negative (Rh−)
-> Rh antigen is absent (e.g., Type O−)
What are Agglutinogens
- surface antigens on RBCs
- screened by immune system
What are Agglutinins
-antibodies in plasma
-attack antigens on foreign RBCs
->causing agglutination (clumping) of foreign cells
The 4 types of agglutinis
-Type A blood has Anti-B antibodies
-Type B blood has Anti-A antibodies
- Type O blood has Both anti-A and anti-B antibodies
- Type AB blood has Neither anti-A nor anti-B antibodies
- Only sensitized Rh−blood has anti-Rh antibodies
What is a Cross-reaction (transfusion reaction)
- may occur in transfusion of blood or plasma from one person to another
- occurs if donor and recipient blood types are not compatible
- Plasma antibody meets its specific surface antigen
->RBCs agglutinate and may hemolyze
What is compatability testing
- performed in advance of transfusions
- cross-match testing
-> reveals cross-reactions between donor’s RBCs and recipient’s plasma - Type O− is the universal donor
-> but cross-reactions can still occur because at least 48 surface antigens exist besides A and B
What are white blood cells
-also called leukocytes
-have nuclei and other organelles
-lack hemoglobin
- a small fraction of WBCs circulate in blood
- all can migrate out of bloodstream
- all are capable of amoeboid movement
-all are attracted to specific chemical stimuli
->positive chemotaxis
- some are phagocytic
What are the wbc 3 functions
- defending body against pathogens
- removing toxins and wastes
- attacking abnormal or damaged cells
Where are most wbc found in
- connective tissue proper, in organs of lymphatic system
What are the 5 types of wbcs
Neutrophils
Eosinophils
Basophils
Monocytes
Lymphocytes
What are platelets (thrombocytes)
- cell fragments involved in clotting system
- circulate for 9–12 days
- removed by phagocytes, mainly in spleen
- 150,000 to 500,000 per microliter of blood
- one-third of platelets in body are stored in vascular organs like the spleen
-> mobilized during a circulatory crisis
What are the 3 functions of platelets
- release important clotting chemicals
- temporarily patch damaged vessel walls
- reduce size of break in vessel wall
What are 2 examples of supporting connective tissues
cartilage and bone
What are cartillage
- provides shock absorption and protection
- matrix is a firm gel
->contains polysaccharide derivatives called chondroitin sulfates - cells in the matrix are chondrocytes
->in chambers called lacunae
What makes up cartilage structure (2)
-avascular
->chondrocytes produce antiangiogenesis factor that discourages formation of blood vessels
- perichondrium
->outer, fibrous layer (for support and protection)
->inner, cellular layer (for growth and maintenance)
What are 3 types of cartillage
- hyaline cartilage
- elastic cartilage
-fibrocartilage
What is hyaline cartilage. functions and location
- most common type
- provides stiff/ somewhat flexible support
- tough and flexible - reduces friction between bones
- found in synovial joints, rib tips, sternum, and trachea
What is elastic cartillage, functions and location
- supportive but bends easily
- found in external ear and epiglottis
What is fibrocatillage, functions and location
- very durable and tough
- limits movement & prevents bone-to-bone contact
- found around joints, between pubic bones, and between spinal vertebrae
What is bone
- for weight support
- calcified (made rigid by calcium salts)
- resists shattering (flexible collagen fibers)
What is the periosteum
- covers bone
- fibrous (outer) and cellular (inner) layers
What are the 4 principal bone cells
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Osteoclasts
What are osteogenic cells
- stem cells that arise from embryonic mesenchyme
- multiply continuously & give rise to most other bone cell types
What are osteoblasts
- bone-forming cells
- form single layer under endosteum & periosteum & are non-mitotic
- synthesise soft organic matter of matrix - hardens by mineral deposition
- stress stimulates osteogenic cells to multiply & increase number of osteoblasts - reinforces bone
- secrete hormone osteocalcin
What are osteocytes
- former osteoblasts - trapped in matrix they deposit
- reside in lacunae - small cavities
- lacunae connected by canaliculi
- cytoplasmic processes extend into canaliculi & contact processes of other osteocytes
- canaliculi allows change of materials w blood
- gap junctions allow for passage of nutrients, wastes, signals
- act as strain sensors - bone produces biochemical signals that regulate bone remodeling (shape & density changes that are adaptive)
What are osteoclasts
- bone-dissolving cells found on bone surface
- large cells formed by fusion of several stem cells - multiple nuclei in each cell
- ruffled border (large surface area) faces bone
- often reside in resorption bays (pits in bone surface)
- dissolving bone is part of bone remodeling
What is bone structure made up of
- 1/3 organic & 2/3 inorganic matter
- Organic matter synthesized by osteoblasts
->collagen, carbohydrate–protein complexes [glycosaminoglycans, proteoglycans & glycoproteins - inorganic matter
->85% hydroxyapatite (crystallized calcium phosphate salt)
->10% calcium carbonate
->other minerals (fluoride, sodium, potassium, magnesium)
What material is bone
- composite material - combination of ceramic & a polymer
- hydroxyapatite & other minerals are the ceramic & collagen (protein) the polymer
What does the ceramic portion of bone allow
- bone to support body weight without sagging
-> rickets - caused by mineral deficiency resulting in soft, deformed bones
What does the polymer of bone allow
- gives some flexibility
- osteogenesis imperfecta (brittle bone disease) results from defect in collagen deposition
What is spongy bone
- lattice of bone covered with endosteum
- slivers of bone called spicules
- thin plates of bone called trabeculae
-> spaces filled with red bone marrow - few osteons & no central canals
->all osteocytes close to bone marrow - provides strength with minimal weight
->trabeculae develop along stress lines
What is Ossification
or osteogenesis - the formation of bone
How does bone develop in human fetus, 2 ways
- Intramembranous ossification [within membrane]
->produces flat bones of skull & clavicle in fetus
->thickens long bones throughout life - Endochondral ossification [within cartilage]
->all other bones
What is bone remodelling
- absorption & deposition
- occurs throughout life - 10% of skeleton per year
->repairs microfractures, releases minerals into blood, reshapes bones in response to use & disuse
What is Wolff’s law of bone
- architecture of bone determined by mechanical stresses placed on it
- remodeling is collaborative & precise action of osteoblasts & osteoclasts
- bony processes grow larger in response to mechanical stress
What is mature bone
- a metabolically active organ
- involved in own maintenance of growth & remodeling
- exerts influence over body by exchanging minerals with tissue fluid
- disturbance of calcium homeostasis in skeleton disrupts function of other organ systems
- especially nervous & muscle tissue
What is mineral deposition
- Ca+, phosphate & other ions are taken from blood & deposited in bone
-osteoblasts produce collagen fibers that spiral length of osteon
-fibres become encrusted with minerals
->hydroxyapatite crystals
->first few crystals act as seed crystals that attract more Ca+ & phosphate from solution
What is abnormal calcification
(ectopic ossification)
- formation of a calculus (calcified mass) in otherwise soft organ [lung, brain, eye, muscle, tendon or artery (arteriosclerosis)]
Describe the process of mineral deposition/reasborption
-process of dissolving bone & releasing minerals into blood performed by osteoclasts at ruffled border
->H- pumps in membranes secrete H- into space between osteoclast & bone surface
->Cl- ions follow by electrical attraction
->hydrochloric acid (pH 4) dissolves bone minerals
->acid protease enzyme digests collagen
What is hypocalcemia
deficiency in Ca+ in blood
- changes membrane potentials & causes overly excitable nervous system & tetany (muscle spasms)
->Vitamin D deficiency, diarrhoea, thyroid tumors, underactive parathyroid glands
->pregnancy & lactation increase risk of hypocalcemia
What is hyperclycaemia
- excessive Ca+ levels
- makes ion channels less responsive & thus nerve & muscle are less excitable
- can cause muscle weakness, slow reflexes, cardiac arrest
How is calcium homeostasis regualted
- Depends on balance between dietary intake, urinary & faecal losses, & exchanges between osseous tissue
- Calcitriol, Calcitonin, Parathyroid hormone
What is calcitriol
- most active form of vitamin D
skin uses UV radiation to produce D_3
liver converts D3 to calcidiol
kidney converts that to calcitriol
raises blood Ca+ level – essential for bone deposition - increases Ca+ absorption by small intestine & Ca+ resorption from skeleton
- stimulates osteoblasts to release chemical that stimulates production of osteoclasts
- weak promoter of kidney reabsorption of Ca+ ions – fewer lost in urine
What is calcitonin
- secreted by cells of thyroid gland when blood Ca+ levels rise too high
- lowers blood Ca+ concentration in two ways:
->inhibits osteoclasts thereby reducing bone resorption
->stimulates osteoblasts to deposit calcium into bone - important in children, weak effect in adults
- osteoclasts more active in children due to faster remodeling
- may inhibit bone loss in pregnant & lactating women
What is the parathyroid hormone
- from parathyroid glands [on posterior surface of thyroid gland]
-released when blood Ca+ levels low
How in 4 ways does the parathyroid hormone raise CA+ blood lvls
- stimulates osteoblasts to secrete RANKL - increases osteoclast population & bone resorption
- promotes Ca+ reabsorption by kidneys - less lost in urine
- promotes final step of calcitriol synthesis in kidneys, enhancing calcium-raising effect of calcitriol
- inhibits collagen synthesis by osteoblasts, inhibiting bone deposition
