Tissues Flashcards
histology
study of tissues
pathologist
looks for tissue changes that indicate disease
4 basic tissues
epithelial, connective, muscle, nerve
epithelial tissues
covers surfaces b/c cells are in contact. lines hollow organs, cavities, and ducts. forms glands when cells sink under the surface
Connective tissue
material found between cells. supports and binds structures together. stores energy as fat. provides immunity to disease
muscle tissue
cells shorten in length producing movement
nerve tissue
cells that conduct electrical signals. detects charges inside and outside the body. responds with nerve impulses
origin of tissues
- Primary germ layers within the embryo
- -endoderm
- -mesoderm
- -ectoderm
Tissue derivations
- epithelium from all three germ layers
- connective tissue and muscle from mesoderm
- nerve tissue from ectoderm
Biopsy
removal of living tissue for microscopic examination
- surgery
- needle biopsy
Useful for diagnosis, especially cancer.
Tissue preserved, sectioned and stained before microscopic viewing
5 Cell Junctions
Tight Junctions, Adherens juctions, gap juctions, desmosomes, hemidesmosomes
Tight Junctions
- watertight seal between cells
- plasma membranes fused with a strip of proteins
- common between cells that line GI and bladder
Adherens Junctions
- Holds epithelial cells together
- Structural components
- Plaque (dense layer of proteins inside the cell membrane)
- Microfilaments extend into cytoplasm
- integral membrane proteins connect to membrane of other cell
Desmosomes
- resist cellular separation and cell disruption and cell disruption
- similar structure to adherens junction except intracellular intermediate filaments cross cytoplasm of cell
- cellular support of cardiac muscle
hemidesmosomes
half a desmosome
- connect cells to extracellular material- basement membrane
gap junctions
- tiny space between plasma membranes of two cells
- crossed by protein channels called connexons forming fluid filled tunnels
- cell communication with ions and small molecules
- muscle and nerve impulses spread from cell to cell hearth and smooth muscles of gut
Epithelial Tissue- general features
- closely packed cells forming continuous sheets
- cells sit on basement membrane
- apical (upper) free surface
- avascular– without blood vessels (nutrients diffuse in from underlying connective tissue)
- good nerve supply
- rapid cell division
- covering/lining versus glandular types
basement membrane
- basal lamina (from epithelial cells; collagen fibers)
- reticular lamina (secreted by connective tissue cells; reticular fibers)
- holds cells to connective tissue
- guide for cell migration during development
Types of epithelium
- covering and lining epithelium
- glandular epithelium
Covering and lining epithelium
- epidermis of skin
- lining of blood vessels and ducts
- lining respiratory, reproductive, and urinary and GI tract
Glandular epithelium
- secreting portion of glands
- thryoid, adrenal, and sweat glands
Classification of epithelium
Classified by arrangement of cells into layers
- simple= one cell layer thick
- stratified= many cell layers thick
- pseudostratified= single layer of cells where all cells don’t reach apical surface (nuclei found at different levels so it looks multilayered)
Classified by shape of surface cells
- Squamous- flat
- cuboidal= cube-shaped
- columnar= tall column
- transitional= shape varies with tissue stretching
Simple Squamous Epithelium
single layer of flat cells
- lines blood vessels (endothelium), body cavities (mesothelium)
- very thin–controls diffusion, osmosis, and filtration
- nuclei centrally located
cells in direct contact with eachother
Simple Cuboidal Epithelium
- Single layer of cube shaped cells viewed from the side
- nuclei round and centrally located
- lines tubes of kidney
- absorption or secretion
Nonciliated Simple Columnar
- Single Layer of rectangular cells
- unicellular glands= goblet cells secrete mucus (lubricate GI, respiratory, reproductive and urinary systems)
- microvilli=fingerlike cytoplasmic projections- for absorption in GI tract (stomach to anus)
Ciliated Simple Columnar
- Single layer rectangular cells with cilia
- mucus from goblet cells moved along by cilia (found in respiratory system and uterine tubes)
stratified squamous epithelium
- several layers thick
- surface cells flat
- keratinized= surface cells dead and filled with keratin (skin- epidermis)
- nonkeratinized= no keratin in moist living cells at surface (mouth, vagina)
Pap Smear
- collect sloughed off cells of uterus and vaginal walls
- detects cellular changes (precancerous cells)
- annually for women over 18 or if sexually active
Stratified cuboidal epitherlium
- multilayered
- surface cells cuboidal - rare (only found in sweat gland ducts and male urethra)
Stratified columnar epithelium
multilayered, surface cells columnar, rare (very large ducts & part of male urethra)
transitional epithelium
multilayered, surface cells vary in shape from round to flat if stretched, lines hollow organs that expand from within (urinary bladder)
pseudostratified
- single cell layer
- all cells attach to basement membrane but not all reach free surface
- nuclei at varying depths
- respiratory system, male urethra & epidiymis
glandular epithelium
- derived from epithelial cells that sank below the surface during development
- Exocrine glands- cells that secrete– sweat, ear wax, saliva, digestive enzymes onto free surface of epithelial layer; connected to the surface by tubes (ducts); unicellular glands or multicellular glands
- endocrine- secrete hormones into bloodstream; hormones help maintain homeostasis
structural classification of exocrine glands
- unicellular are single celled glands- goblet cells
- multicellular glands- branched (compound) or unbranched (simple); tubular or acinar (flask like) shape
Methods of glandular secretion
- merocrine- most glands (cells release their products by exocytosis— saliva, digestive enzymes & sweat)
- apocrine- smelly sweat & milk; upper part of cell possibly pinches off and dies
- holocrine- oil gland; whole cells die & rupture to release their products
Connective Tissues
- cells rarely touch due to extracellular matrix
- matrix (fibers & ground substance secreted by cells)
- consistency vaies from liquid, gel to solid
- does not occur on free surface
- good nerve & blood supply except cartilage & tendons
Cell types
blast type cells cyte type cells macrophages plasma mast cells adipocytes
Blast type cells
- retain ability to divide and produce matrix (fibroblasts, chondroblasts, osteoblasts)
cyte type cells
mature cell that con not divide or produce matrix (chondrocytes and osteocytes)
macrophages
- develop from monocytes
- engulf bacteria and debris by phagocytosis
Plasma cells
- develop from B lymphocytes
- produce antibodies that fight against foreign substances
Mast cells
produce histamine that dilate small blood vessels
Adipcytes
fatt cells- store fat
Connective Tissue Ground Substance
- supports the cells and fibers
- helps determine the consistency of the matrix- fluid, gel or solid
- contains many large molecules- hyaluronic acide is thick, viscous and slippery; condroitin sulfate is jellylike substance providing support; adhesion proteins (fibronectin) binds collagen fibers to ground substance
Types of Connective Tissue Fibers
Collagen, Elastin, Reticular
Collagen
(25% of protein in your body)
- tough, resistant to pull, yet pliable
- formed from the protein collagen
Elastin
(lungs, blood vessels, ear cartilage)
- smaller diameter fibers formed from protein elastin surrounded by glycoprotein (fibrillin)
- can stretch up to 150% of relaxed length and return to original shape
Reticular
(spleen and lymph nodes)
- thin, branched fibers that form framework of organs
- formed from protein collagen
Marfan Syndrome
- inherited disorder of fibrillin gene
- abnormal development of elastic fibers
- tendency to be tall with very long legs, arms, fingers, and toes
- live threatening weakening of aorta may lead to rupture
Embryonic Connective Tissue: Mesenchyme
- Irregularly shaped cells
- in semifluid ground substance with reticular fibers
- gives rise to all other types of connective tissue
Embryonic Connective Tissue: Mucous Connective Tissue
- Star shaped cells in jelly-like ground substance
- found only in umbilical cord
Mature Connective Tissue
- loose connective tissue
- dense connective tissue
- cartilage
- bone
- blood
- lymph
Loose Connective Tissue
- loosely woven fibers throughout tissues
- types: areolar, adipose, reticular
Loose Connective Tissue: Areolar
Cell types: fibroblasts, plasma cells, macrophages, mast cells and a few WBC
- all 3 of fibers present
- gelatinous ground substance
Adipose Tissue
- peripheral nuclei due to large fat storage droplet
- deeper layer of skin, organ padding, yellow marrow
- reduces heat loss, energy storage, protection
- brown fat found in infants has more blood vessels and mitochondria and responsible for heat generation
Reticular Connective Tissue
- network of fibers & cells that produce framework of organ
- holds organ together (liver, spleen, lymph nodes, bone marrow)
Dense Connective Tissue
- more fibers present but fewer cells
- types: dense regular, dense irregular, elastic
Dense Regular Connective Tissue
- collagen fibers in parallel bundles with fibroblasts between bundles of collagen fibers
- white, tough and pliable when unstained (forms tendons)
- also known as white fibrous connective tissue
Dense Irregular Connective Tissue
- collagen fibers are irregularly arranged (interwoven)
- tissue can resist tension from any direction
- very tough tissue- white of eyeball, dermis of skin
Elastic connective tissue
- branching elastic fibers and fibroblasts
- can stretch & still return to original shape
- lung tissue, vocal cords, ligaments between vertebrae
Cartilage
- network of fibers in rubbery ground substance
- resilient and can endure more stress than loose or dense connective tissue
types: hyaline, fibrocartilage, elastic
hyaline cartilage
- bluish-shiny white rubbery substance
- chondrocytes sit in spaces called lacunae
- no blood vessels or nerves so repair is very slow
- reduces friction at joints as articular cartilage
Fibrocartilage
- many more collagen fibers cause rigidity & stiffness
- strongest type of cartilage (intervertebral discs)
Elastic Cartilage
- elastic fibers help maintain shape after deformations
- ear, nose, vocal cartilages
Growth & Repair of Cartilage
- Grows and repairs slowly because its avascular
- interstitial growth- chondrocytes divide and form new matrix; occurs in childhood and adolescence
- appositional growth- chondroblasts secrete matrix onto surface; produces increase in width
Bone (osseous) Tissue
Spongy- sponge like with spaces and trabeculae (struts of bone surrounded by red bone marrow); no osteons (cellular organization)
Compact bone- solid, dense bone; basic unit of structure is osteon (haversian system)
*protects, provides movement, stores minerals, site of blood cell formation
Osteon
lamellae (rings) of mineralized matrix
- calcium & phosphate– gives it its hardness
- interwoven collagen fibers provide strength
osteocytes
in spaces (lacunae) in between lamellae
Canaliculi
tiny canals that connect cell to cell
connective tissue with a liquid matrix
plasma
Cell types
RBC (erythrocytes), WBC (leukocytes), Platelets- provide clotting, immune functions, and carry O2 and CO2
Lymph
Interstitial fluid being transported in lymphatic vessels
- contains less protein than plasma
- move cells and substances (lipids) from one part of the body to another
Membranes
epithelial layer sitting on a thin layer of connective tissue (lamina propria)
types: mucous, serous, synovial, cutaneous
Mucous Membranes
lines a body cavity that open to the outside (mouth, vagina, anus, etc)
- epithelial cells form a barrier to microbes
- tight junctions between cells
- mucous is secreted from underlying glands to keep surface moist
Serous Membranes
Simple squamous cells overlying loose CT layer
- squamous cells secrete slippery fluid
- lines a body cavity that does not open to the outside such as chest or abdominal cavity
Examples: pleura, peritoneum and pericardium
- membrane on walls of cavity- parietal
- membrane over organs- visceral layer
Synovial Membranes
line joint cavities of all freely moveable joints
- no epithelial cells- just special cells that secrete slippery fluid
Muscle
cells that shorten; provide us with motion, posture and heat
types: skeletal, cardiac, smooth
Skeletal Muscle
cells are long cylinders with many peripheral nuclei
- visible light and dark banding (looks striated)
- voluntary or conscious control
Cardiac Muscle
Cells are branched cylinders with one central nuclei
- involuntary and striated
- attached to and communicate with each other by intercalated discs and desmosomes
Smooth Muscles
Spindle shaped cells with single central nucei
- walls of hollow organs (blood vessels, GI tract, bladder)
- involuntary and striated
Nerve Tissue
Cell types- nerve cells and neuroglial (supporting) cells
- nerve cell structure
- nucleus & long cell processes conduct nerve signals
dentrite- signal travels towards the cell body
axon- single travels away from cell body
Tissue Engineering
new tissues grown in the laboratory (skin and cartilage)
-scaffolding of cartilage fibers is substrate for cell growth in culture
Tissue Repair: Restoring Homeostasis
Worn out, damaged tissue must be replaces
- Fibrosis= replacement with stromal connective tissue cells (scar formation)
- Regenerations= replacement with orginal cell types (parenchymal cells)
- some cells can divide (liver & endothelium)
- some tissues contain stem cells that can divide (bone marrow, epithelium of gut & skin)
- some cell types can not divide & are not replaced (muscle and nervous tissue)
Conditions affecting tissue repair
Nutrition- adequate protein for structural components; vitamin C production of collagen and new blood vessels
Proper blood circulation- delivers O2 and nutrients and removes fluids & bacteria
With aging- collagen fibers change in quality; elastin fibers fragment and abnormally bond to calcium; cell division and protein synthesis are slowed
Sjogrens Syndrome
Autoimmune Disorder producting exocrine gland inflammation
- dryness of mouth and eyes
- 20% of older adults show some signs
Systemic Lupus Erythematosus
Autoimmune disorder (causes unknown)
- chronic inflammation of connective tissue
- nonwhite women during childbearing years
- painful joints, ulcers, loss of hair, fever
- life-threatening if inflammation occurs in major organs– liver, kidney, heart, brain, etc
