Histology Lecture #1

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yodog818
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Histology Lecture #1
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2014-03-28 20:17:23
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Bio 422
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  1. hemotoxylin (and eosin) stain
    • H&E is the most widely used histological stain
    • hemotoxlin is extracted from the log wood tree this stain is used to visualize cell nuclei since it has dye-metal complexes that bind to DNA 
    • eosin is an acidic dye that stains basic/eosinophilic cellular components like protein and cytoplasm
  2. carmine (cochineal) stain
    • carminic acid harvested from cochineal insects is used to make the carmine stain, a type of natural stain
    • carmine stain is an intense red dye used to stain glycogen, and requires the use of a mordant like aluminum
    • mordant -a substance, typically an inorganic oxide, that combines with a dye or stain and thereby fixes it in a material
  3. congo red stain
    • red stain with strong non-covalent affinity to cellulose fibers
    • used as a cytoplasmic and erythrocyte stain, and to help visualize cell functions
  4. Wright's stain
    • a neutral stain used to differentiate the blood cell types like lymphocytes, basophils, eosinophils, and neutrophils
    • can stain blood and bone marrow
  5. the seven cell types
    • epithelial cell
    • connective tissue cell
    • nerve cell
    • blood cell
    • bone cell
    • muscle cell
    • cartilage
  6. the four tissue types
    • epithelial tissue
    • connective tissue (special and proper)
    • muscle tissue
    • nerve tissue
  7. epithelium
    • one of the four basic tissue types
    • epithelium is an avascular tissue that covers body surfaces, lines body cavities, and form many glands and organs
    • three principal characteristics:
    • i) cells adhere to one another by adhesion molecules that form cell junctions
    • ii) cells have three surface domains (free/apical, lateral, basal)
    • iii) their basal membrane is attached to underlying basement membrane
  8. simple squamous epithelium: description, location, function
    • description: flat epithelium that are wider than they are tall, with a thickness of one layer
    • location: lining of blood and lymphatic vessels (endothelium), lining of pleura and peritoneum and pericardium (mesothelium), alveoli of lungs, Bowman's capsule and Loop of Henle in kidneys 
    • function: protection of underlying tissues; regulation and exchange of chemicals between underlying tissues; secretion of hormones, sweat, mucus, and other products


  9. simple cuboidal epithelium: description, location, function
    • description: epithelium that are just as wide as they are tall, in a single layer
    • location: thyroid, ovary, collecting tubes of the kidneys, bile duct
    • function: protection of underlying tissues; regulation and exchange of chemicals between underlying tissues; secretion of hormones, sweat, mucus, and other products
  10. simple columnar epithelium (non-ciliated and ciliated): description, location, function
    • description: epithelium that are taller than they are wide, in a single layer; ciliated have hair-like projections called cilia
    • location non-ciliated: stomach, intestine, rectum, mammary gland duct
    • location ciliated: Fallopian tubes, uterus, bronchii, central part of spinal cord
    • function non-ciliated: protection of underlying tissues; regulation and exchange of chemicals between underlying tissues; secretion of hormones, sweat, mucus, and other products
    • function ciliated: move mucus and other substances with their cilia

  11. stratified squamous epithelium: description, location, function
    • description: layers of epithelial cells with the top-most layer consisting of squamous epithelium; may be keratinized or non-keratinized
    • location non-keratinized: oral cavity, esophagus, vagina, anal cavity
    • location keratinized: epidermis of palm and sole of the foot
    • function non-keratinized: this type of epithelium is well suited to areas in the body subject to constant abrasion, as it is the thickest and layers can be sequentially sloughed off and replaced before the basement membrane is exposed
    • function keratinized: structural keratin protein provides additional protection from abrasion, desiccation, and bacterial invasion
  12. stratified squamous epithelium: description, location, function
    • description: layers of epithelial cells with the top-most layer consisting of cuboidal epithelium
    • location: sweat gland duct, salivary gland duct
    • function: provide protection for ducts
  13. stratified columnar epithelium: description, location, function
    • description: layers of epithelial cells with the top-most layer consisting of columnar epithelium; can be non-ciliated or ciliated
    • location non-ciliated: parts of the pharynx, uterus, male urethra
    • location ciliated: part of larynx, fetal esophagus
    • function: secretion and protection
  14. pseudostratified columnar epithelium (ciliated, non-ciliated): description, location, function
    • description:  a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelium
    • location: trachea, parathyroid gland, lacrimal sac 
    • function: secretion or absorption
  15. transitional epithelium: description, location, function
    • description: a type of tissue consisting of multiple layers of epithelial cells which can contract and expand, changing the epithelium cell type; may be stratified or single layered
    • location: bladder, uterus, part of urethra
    • function: allows distension of urinary glands during urine accumulation and contraction during emptying process; metaplasia results if process is irreversible
  16. regeneration of epithelial tissue
    stratum germinatvium of basement membrane responsible for regeneration and can vary from 4-6 days in the stomach to 25-28 days in the epidermis
  17. embryogenesis
    • zygote -> morula -> blastula -> gastrula (after 15-20 days)
  18. germ layers
    • ectoderm: brain, hair, nails, lens of eyes, retina
    • endoderm: stomach, lungs, intestines, liver, bladder
    • mesoderm: connective tissue including bone and blood and cartilage, muscles, kidneys, gonads
  19. three components of connective tissue
    connective tissue cells, fibers, and ground substance/ extracelluler matrix
  20. CT cells: proper
    • proper CT divided into loose (or areolar) and dense; loose CT is only found as irregular while dense CT can be regular or irregular
    • loose CT has fewer fibers and more cells and ground substances
    • dense CT have more fibers and less ground substances and cells
  21. lymphoid tissue
    cells and organs that make up the lymphatic system, such as white blood cells (leukocytes), bone marrow, and the thymus, spleen, and lymph nodes
  22. myeloid tissue
    • a biologic tissue with the ability to perform hematopoiesis
    • it is mainly found as the red bone marrow in bones, and is often synonymous with this, and in the liver and spleen in fetuses
  23. areolar loose CT
    • location: primarily located beneath the epithelia that cover the body surfaces and line the internal surfaces of the body
    • loose CT is thus the initial site where pathogenic agents such as bacteria that have breached an epithelial surface are challenged and destroyed by cells of the immune system; it is therefore the site of inflammatory and immune reactions
    • function: attaches epithelium to underlying tissues and allows for diffusion of nutrients to epithelial cells
    • cells found in loose CT: mesenchyme, fibroblast, macrophages, eosinophils, plasma cells, mast cells, fat cells
  24. reticular loose CT
    • location: lymph nodes, spleen, liver 
    • function: forms supportive framework for these soft organs
  25. adipose loose CT
    • location: under skin, and around organs
    • function: stores lipids (energy), insulation, cushions organ
  26. dense regular CT
    • is the main functional component of tendons, ligaments, and aponeuroses
    • the fibers of dense regular CT are the prominent feature, and there is little ECM fibers and CT cells
    • are arranged in parallel array and are densely packed to provide maximum strength
  27. dense irregular CT
    • contains mostly collagen fibers, cells are sparse and are typically of a single type,the fibroblast, with relatively little ground substance
    • provides significant strength since the fibers are arranged in bundles oriented in various directions that can withstand stresses on organs or structures
    • examples- dermis, periosteum, perichodrium
  28. CT fibers
    • all three fibers synthesized by fibroblasts
    • collagen fibers - most abundant type, fibrils form fibers that then form bundles, are heat sensitive and can be boiled into gelatin
    • elastic fibers - thin long fibers composed of elastin protein, heat insensitive, they allow tissues to respond to stretch and distension
    • reticular fibers - AKA pre-collagen fibers, are acidophilic, thinner than collagen, and arranged in mesh-like pattern that act as framework for tissues and organs
  29. extracellular matrix (ECM)
    • ECM is a structural network that surrounds and supports cells within the CT
    • composed of CT fibers and ground substance
  30. ground substance
    is a clear, viscous substance that is composed of proteoglycans, glycoproteins, and glycosaminoglycans
  31. CT cells: resident cells
    • CT cells that exhibit little movement
    • include fibroblasts, macrophages, adipocytes, mast cells, and adult stem cells
  32. CT cells: wandering/transient cells
    • CT cells that migrate into the tissue from the blood in response to specific stimuli
    • include lymphocytes, plasma cells, monocytes, basophils, eosinophils, and neutrophils
  33. granulocytes vs. agranulocytes
    • leukocytes are arranged into two groups
    • granulocytes contain granules - basophils, eosinophils, neutrophils
    • agranulocytes lack specific granules - lymphocytes and monocytes
  34. fibroblast: description, location, function
    • description: elongated or disc-like structure with thin processes
    • location: all CT
    • function: synthesis of collagen, elastic, and reticular fibers as well as ground substance
  35. macrophage: description, location, function
    • description: identifiable when displaying phagocytotic activity, has kidney shaped nucleus, abundant lysosomes in cytoplasm
    • location: CT due to immune response or to recycle cellular debris
    • function: derived from monocytes, macrophages are responsible for phagocytosis of foreign material and cellular debris, also involved in communication with other immune cells
  36. mast cell: description, location, function
    • description: large acidophilic cells with spherical nucleus and cytoplasm filled with large basophilic red staining granules 
    • location: agranular while circulating in blood, mature granules when in CT; mature mast cells found mostly in CT of skin and mucous membranes but not in CNS (brain, spinal cord), also found in thymus
    • function: similar to basophils, their secretory granules contain histamine, heparin, and serotonin
    • histamine used in allergic response, heparin in blood coagulation, serotonin as a vasoconstrictor
  37. adipocyte/adipose/fat cell: description, location, function
    • description: large, clear cells with nucleus pushed against plasma membrane by fat
    • location: located throughout loose CT, when accumulated they form adipose tissue
    • function: specialized to store fat and also to produce a variety of hormones
  38. plasma cells: description, location, function
    • description: large ovoid cell with lots of cytoplasm, nucleus displays a cartwheel pattern due to alternating clumps of dark heterochromatin and clear euchromatin
    • location: CT of the gastrointestinal and respiratory tracts
    • function: derived from B lymphocytes, they produce antibodies during an immune response
  39. basophil: description, location, function
    • description: stain blue, have large granules in cytoplasm
    • location: in circulation in the bloodstream
    • function: similar to mast cells (except basophils are mature when in the blood), have secretory granules that contain histamine, heparin, serotonin
  40. eosinophil: description, location, function
    • description: have many red stained granules, have bilobed nucleus that stains blue
    • location: circulate in blood and migrate to CT
    • function: contain two types of granules that are secreted during an allergic reaction or parasitic infection
  41. neutrophil: description, location, function
    • description: multilobal nucleus (usually 2-4), named after lack of cytoplasmic staining
    • location: circulate the blood and migrate to CT
    • function: recognize, bind to, and phagocytize bacteria and other infectious agents
  42. monocytes: description, location, function
    • description: are the largest of the leukocytes and have an indented nucleus
    • location: travel from the bone marrow to the body tissues where they differentiate into other cells
    • function: precursors of the cells of the mononuclear phagocytotic system (macrophages in CT, spleen, lymph nodes, also liver macrophages AKA Kupffer cells and osteoblasts)
  43. CT special
    cartilage, bone, lymph, and blood
  44. melanocytes
    • cells found in the basal layer of the epidermis that produce the group of pigments called melanin
    • melanin helps dissipate UV radiation and the amount of melanin produced in melanocytes determine skin tone
  45. cartilage: description and types
    • like other CT types, all three are made up of cells, fibers, and ground substance
    • in contrast to other CT, cartilage is avascular and relies on diffusion through the ECM for nutrition and elimination of wastes
    • cartilage provides structural support for soft tissues, allows flexibility without distortion, and resistance to compression
    • composed of chondrocytes and chondrblasts
    • three types are hyaline cartilage, elastic cartilage, fibrocartilage
  46. hyaline cartilage
    • most common, 40% of all cartilage
    • surrounded by perichondrium that aids in its growth and repair
    • hyaline can transform into bone during endochondrial ossification
    • articular cartilage refers to hyaline cartilage on the articular surface of bones
    • hyaline cartilage located between the ribs, at the ends of bones where they form joints, in the larynx, and in the trachea
  47. elastic cartilage
    • similar to hyaline except fibers in the ECM are mostly elastin instead of collagen
    • surrounded by inner and outer perichondrium
    • located in the epiglottis, external ear, and larynx
  48. fibrocartilage
    • characterized by large amounts of irregular and dense collagen fibers in its matrix that are oriented in the direction of functional stress, has less ground substance
    • lacks chondroblasts (mesenchyme differentiates directly into chondrocytes) and a perichondrium
    • located in the intervertebral disks, symphysis pubis, and the meniscus and other joints
  49. perichondrium
    • dense irregular CT that surrounds hyaline and elastic cartilage
    • inner layer (AKA chondrogenic region) has less fibers and more cells; chondroblasts develop in this region and under go appositional growth
    • outer layer (AKA fibrous region) has less cells, especially fibroblasts) and more collagen fiber
  50. lacuna (pl. lacunae)
    • means "lake" in latin
    • a lacuna is a cavity in the matrix containing an osteocyte in bone or chondrocyte in cartilage
    • more than one cell can occupy a lacuna
  51. chondroblasts vs. chondrocytes
    • mesenchymal stem cells give rise to chondroblasts (in the chondrogenic region of perichondrium) which give rise to chondrocytes
    • chondroblasts that become embedded in the matrix are called chondrocytes, which occupy lacunae
    • groups of chondrocytes are called isogens
  52. appositional vs. interstitial growth in cartiliage
    • appositional growth occurs when inner layers of perichondrium cells divide and differentiate into chondroblasts, this growth increases the cartilage mass by adding to the surface
    • interstitial growth results in the enlargement of internal mass of the cartilage by mitotic divisions of existing chondrocytes and continued deposition of the extracellular matrix
  53. endochondral ossification
    • forms most bones in body including longs bones, and also used in healing bone fractures
    • mesenchymal cells proliferate and differentiate into chondroblasts that produce cartilage matrix


  54. intramembranous ossification
    • forms the flat bones of the mandible, skull, and clavicle
    • bone development not preceded by hyaline cartilage, instead bone develops from condensation of CT mesenchyme to form an ossification center
    • mesenchyme cells differentiate directly into osteoblasts that produce the bone matrix (osteoid)
    • the bone matrix becomes calcified, osteoblasts become osteocytes, and the process repeats resulting in production of layers of bone
  55. functions of bone
    provide protection to internal organs, provide attachment site to skeletal muscle, storage of Ca+2 and phosphate
  56. spongy (AKA cancellous) bone
    • less dense than compact bone, making it softer and more flexible
    • found at the ends of long bones and interior of vertebrae
    • contains red bone marrow where hematopoiesis occurs
    • made up of a number of trabecular/cancellous bars separated by CT
  57. compact bone - location and structure
    • compact bone is found in long bones
    • denser, harder, and stiffer than cancellous bone and forms the outer shell or cortex of most bones
    • functional unit is the osteon
    • growth of bone stops once it becomes compact bone
  58. lamellae
    • concentric layers of compact bone tissue that surround the central/Haversian canal in an osteon
    • interstitial lamellae exist between osteons
  59. canaliculi
    • small canals between lacunae of ossified bone
    • radiating processes of osteocytes project into these canals
    • these canals facilitate the exchange of nutrients and wastes between osteocytes in lacunae
  60. Haversian canal
    canal at the center of an osteon that houses blood vessels and nerve cells
  61. Volkmann (perforating) canals
    • canals that run perpendicular to and join blood vessels from the periosteum to the Haversian canals
    • supplies the organic components of the bone matrix
  62. periosteum
    • dense irregular CT membrane that covers the outer surface of all bones (except joints of lone bones)
    • two layers are inner (AKA osteogenic, site of osteoprogenitor cells) layer and outer fibrous layer (site of fibroblasts)
    • periosteum of the skull is called pericranium
  63. Sharpey's fibers
    • collagenous fibers that attach bone to periosteum
    • also provide attachment for muscles and tendons
  64. endosteum
    • thin layer of dense irregular CT that lines the surface of bony tissue that forms the cavity of long bones
    • consists of single layer of osteoprogenitor cells
  65. osteoprogenitor cells
    • undifferentiated, pluripotent cells derived from mesoderm and found in the inner layer of periosteum as well as the endosteum
    • provides nutrition and continuous supply of osteoblasts for growth, repair, and remodeling
  66. osteoblasts
    • located on surface of bone
    • morphologically flat and stains blue
    • synthesize and secrete bone matrix (osteoid)
    • including collagen fibers, proteoglycans, alkaline phosphatase
    • has receptors for parathyroid hormone, which causes blood concentration of Ca+2 to increase via activation of osteoclasts by osteoblasts
  67. osteocytes
    • mature forms of osteoblasts found in lacunae in the bone matrix (only one in each lacuna)
    • cytoplasmic extensions enter canaliculi and form a network with other osteocytes; connections allow the exchange of nutrients and wastes with the blood vessels of the Haversian canal
  68. osteoclasts
    • derived from hemopoietic progenitor cells
    • these multinucleated cells resorbs or disassembles bone during remodeling
  69. smooth muscle
    • involuntary non-striated muscle located in the bladder, uterus, GI tract, and walls of blood vessels
    • morphologically has a fusiform (spindle) shape, single nucleus, and CT between cells
  70. skeletal muscle
    • voluntary striated muscle attached to bone
    • morphologically long and cylindrical and are multinucleated (nuclei in periphery) due to fusion of numerous myoblasts
    • functional unit is the sarcomere
  71. sarcomere components
    • I band - actin not superimposed by myosin
    • A band - marks extent of myosin filament
    • Z line/disc - borders that separate sarcomeres
    • H band - zone of myosin not superimposed by actin
    • M band - narrow dark band in the center of the H band and bisects the A band; marks where adjacent myosin filaments are linked
  72. skeletal muscle organization
    • skeletal muscle consists of bundles of fibers called fascicles, each fascicle consists of muscle fibers, each muscle fiber consists of myofibrils, each myofibril consists of myofilaments
    • myofilaments are actin (thin) and myosin (thick)

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