Anatomy Histology Notes

Tissues and Histology study in psych

• Tissues - collection of similar cells and the substances surrounding them that work together to perform a specific function. There are four primary types of tissues in the human body: epithelial, connective, muscle, and nervous.

• Specialized cells and the extracellular matrix surrounding them form the tissue level of organization

• extracellular matrix- the composition of the extracellular matrix varies by tissue type and plays a crucial role in providing structural and biochemical support to surrounding cells.

• epithelial and connective tissues are the most diverse in form and function, as they can be found in various shapes and structures, adapting to the specific needs of different organs and systems within the body.

• tissues in the body are interdependent meaning they depend on one another

• histology is the microscopic study of tissues.

• biopsy is the process of removing tissue samples from patients for diagnostic purposes, allowing for the examination of cellular structures and the identification of diseases such as cancer.

• autopsy is an examination of the organs of a dead body to determine the cause of death or to study the changes caused by disease, providing crucial insights into pathological processes and aiding in the understanding of various medical conditions.

  Embryonic tissue

• Approximately 13 or 14 days after fertilization the cells give rise to a new individual called embryonic stem cells, form a slightly elongated disk consisting of two layers called the ectoderm and the endoderm. Cells of the ectoderm then migrate between the two layers to form mesoderm.

• The endoderm is the inner layer which forms lining of the digestive tract and its derivatives.

• The mesoderm is the middle layer which forms tissues such as muscle, bone, and blood vessels

• The ectoderm is the outer layer, forms the skin, and a portion of the ectoderm, called the neuroectoderm, which becomes the nervous system.

• Neural crest cells- groups of cells that break away from the neuroectoderm during development.

  Epithelial Tissue

• Epithelial Tissue is the tissue type that covers the body surfaces, lines cavities and organs, and forms glands, playing a crucial role in protection, absorption, and secretion.

• consists almost entirely of cells with little extracellular matrix between them.

• most epithelial tissues have one free or apical surface not attached to other cells, a lateral surface attached to other epithelial cells and a basal surface.

• The basal surface of most epithelial cells is attached to a basement membrane.

• The basement membrane is a specialized type of extracellular material secreted by the epithelial cells and connective tissue.

• The basement membrane plays an important role in supporting and guiding cell migration during tissue repair.

• specialized cell contacts bind adjacent epithelial cells together.

• blood vessels in the underlying connective tissue do not penetrate the basement membrane, which helps to maintain a distinct separation between the epithelium and the connective tissue, thus contributing to the selective permeability of the epithelial layer. Additionally, the basement membrane contains various proteins, such as collagen and laminin, which provide structural support and facilitate communication between the epithelial cells and the underlying connective tissue.

• epithelial cells maintain abilitily to undergo ,itosis and can replace damaged cells with new epithelial cells

  study during lunch

  functions of epithelial tissue

• protecting underlying structures from abrasion.

• act as a barrier from movement of many substances through epithelial layer.

• permitting the passage of substances

• secreting substances (sweat, mucous)

• absorbing substances.

  Classification of Epithelium

• simple epithelium- consists of a single layer of cells with each cell extending from bm to free surface

• stratified epithelium- consists of more than one layer or cells, but only basal layer of cells attaches the deepest layer to the basement membrane

• pseudostratified columnar epithelium- is a special type of simple epithelium. appears to be stratified but not

• squamous- the cells are flat or scale like

• cuboidal cells are cube shaped they are about as wide as they are tall

• columnar tall and thin similar to column cells are taller than they are wide.

• stratified squamous epithelium- found in areas such as the mouth, esophagus, rectum, and vagina, consists of living cells in the deepest and outermost layer

• keratinized stratified squamous epithelium found in the skin, consists of living cells in the deepest layers and the outer layers are composed of dead cells containing the protein keratin. The dead, keratinized cells give the tissue a durable, moist resistant, dry character.

• transitional epithelium- a unique type of stratified epithelium- lines urinary bladder, ureters, pelvis of kidney, minor and major calyces. - its a barrier function as it provides a robust barrier against urine which is toxic to surrounding tissues due to high solute content.

• selective movement of materials through epithelium is hindered by a stratified epithelium, which is found in areas where protection is a major function. multiple layers of cells in stratified epithelium are a protective role and the outer cells are replaced by cells from deeper layers and a continuous barrier of epithelial cells is maintained by tissue.

• goblet cells- specialized columnar epithelial cells- goblet cells contain abundant organelles responsible for the synthesis and secretion of mucus, such as ribosomes, endoplasmic reticulum, Golgi apparatuses, and secretory vesicles filled with mucus.

cell surfaces

free surfaces of epithelial tissues can be smooth, contain microvilli, be ciliated, or be folded.

• smooth surfaces reduce friction

• microvilli are nonmotile and contain microfilaments. they greatly increase suface area and are found in cells that absorb or secrete such as serous membranes or the lining of the small intestine.

• sterocilia are elongated microvilli. they are found in sensory structures, such as the inner ear, and they play a role in sound detection.

• simply ciliated cuboidal, simple ciliated columnar, and pseudostratified ciliated columnar epithelial tissues are in the respiratory tract where cilia move mucus that contains foreign particles, such as dust, out of the respiratory passages. cillia also found on apical suface of the simple columnar epithelial cells of uterus and uterine tubes. cilia helps to move mucus and oocytes.

cell connections

• lateral and basilar surfaces have structures that hold cells to one another or to the basement membrane. the structures do 3 things, mechanically bind the cells together, help form a permeability barrier, and provide a mechanism for intercellular communication

• epithelial cells secrete glycoproteins that attch the cells to the basement membrane and to one another.

• desmosomes- disk shaped structures with especially adhesive glycoproteins that bind cells to one another and intermediate filaments that extend into the cytoplasm of the cells. mostly found in epithelial tissues that are subjected to stress.

• hemidesmosomes similar to one half of a desmosome attach epithelial cells to the basement membrane.

• tight junctions hold cells together and form a permeability barrier. they consists of a zonula adherens and a zonula occludense, which are found in close association with each other. the zonula adherens is located between the plasma membranes of the adjacent cells and act as a weak glue that holds cells together. zonula prevents the passage of materials between cells. thus water and other substances must pass through epithelial cells which can be actively regulate what is absorbed or secreted.

• gap junction- small specialized contact region between cells containing protein channels that aid intercellular communication by allowing ions and small molecules to pass from one cell to another.

• intercalculated cells - gap junctions between caridac muscle cells in cell to cell connections.

• multicellular glands, but some exocrine glands are composed of a single cell and are called unicellular glands.

• Goblet cells- unicellular glands that secrete mucous of respiratory system.

• Multicellular glands classified - some exocrine glands are composed of single cells called unicellular glands.

• glands that have ducts with few branches are simple, and those with ducts that branch repeatedly are compound.

• further classifications is based on whether ducts end in tubules in saclike structures called acini ( a cluster of small sacs) or alveoli.

• tubular glands can be classified as stright or coiled.

• exocrine glands can also be classified according to how products leave the cell. Merocrine glands such as water producing sweat glands and the exocrine portion of the pancreasm secrete products with no loss of actual cellular material. apocrine glands, such as the milk-producing mammary glands, discharge fragments of the gland cells in the secretion. holocrine glands such as sebaceous oil glands in the skin shed entire cells. Products accumulate in the cytoplasm of each epithelial cell, the cell ruptures and dies, and the entire cell becomes part of the secretion.

• Connective Tissue

• abundant, in every organ in body

• funtions0 enclosing and seprating, connecting tissues to one another, supporting and moving, storing, cushioning and insulating, transporting, protecting cells.

• blasts create the matrix, cytes maintain it, and clasts break down it for remodeling.

• fibroblasts are cells that form fibrous connective tissue and fibrocytes maintain it.

• chondroblasts form cartilage and chondrocytes maintain it.

• osteoblasts form bone, osteocytes maintain it, and osteoclasts break it down.

• adipose-fat cells also called adipocytes contain large amounts of lipid. the lipid ushes the rest of cell contents to the periphery so that each cell appears to contain a large centrally located lipid droplet with a thin layer of cytoplasm around it.

• mast cells are commonly found beneath membranes in loose connective tissues and alond small blood vessels of organs. they contain chemicals such as heparin, histamine, and proteolutic enzymes.

• white blood cells or leukocytes continuously move from blood vessels into connective tissues.

• macrophages are found in some connective tissue types. macrophages are either fixed and do not move through the connective tissue in which they are found or are wandering macrophages and move by ameboid movement throught the connective tissue. they also play role in providing protection against infections.

• undifferentiated mesenchymal cells, sometimes called stem cells are embryonic cells that persist in adult connective tissue.

  extracellular matrix

• extracellular matrix of connective tissue has three major components, protein fibers, ground substance consisting of nonfibrous protein and other molecules, and fluid.

• functional characteristics like ability of bones and cartilage to bear weight, of tendons and ligaments to withstand thension, and of the skins dermis to withstand punctures, abrasions, and other abuses.

  protein fibers of the matrix

• collagen fibers consist of collagen which accounts for one fourth to one third of total body protein, or 6% of body weight.

• within fibroblasts, chains of amino acids collagen a chains are synthesized, and three collagen a chains wind around each other to from a microscopic ropelike helix called a collagen molecule.

• some amino acids are cleaved off of the collagen molecules to produce tropocollagen molecules.

• then tropocollagen molecules are then linked together to make long collagen fibrils.

• reticular fibers are very fine collagen fibers and therefore are not a chemically distinct category of fibers.

• elastic fibers consist of proteins called elastin-which are elastic (shocker)

  other matrix molecules

• two types of large, nonfibrous molecules called hyaluronic acid and proteoglycans, are part of the extracellular matrix. these molecules constitute most of the ground substance of the matrix the shapeless background against which the collagen fibers are seen through the microscope.

• hyaluronic acid is a long, unbranched polysaccharide chain composed of repeating disaccharide units. it gives a very slippery quality to the fluids that contain it.

• a proteoglycan monomer is a large molecule that consists of 80 to 100 polysaccharides, called glycosaminoglycans such as chondroitin sulfate, each attached by one end to a protein core.

• The protein cores of many proteoglycan monomers can attach through link proteins to a long molecule of hyaluronic acid to form a proteoglycan aggregate-which traps large quantities of water, which allows them to return to their original shape when compressed or deformed.

• several adhesive molecules are found in ground substance, these ashesive molecules hold the proteoglycan aggregates together and to structures such as the plasma membrane.

• chondronectin is in the ground substance of cartilage, osteonectin is in the ground substance of bone, and fibronectin is in the ground substance of fibrous connective tissues.

  Classification of Connective Tissue

• classification influenced by protein fibers and the arrangement of protein fibers in the extracellular matrix, protein fibers and ground substance in the extracellular matrix, and a fluid extracellular matrix

  embryonic connective tissue

• called mesenchyme

• made up of irregularly shaped fibroblasts surrounded by abundant, semifluid, extracellular matrix in which delicate collagen fibers are distributed.

  adult connective tissue

• six types loose, dense, connective tissue w/ special properties, cartilage, bone, and blood and hemopoietic tissue

• Loose connective tissue which is sometime referred to as areolar tissue, consists of protein fibers that form a lacy network with numeroud fluid filled spaces. it contains collagen, reticular, and elastic fibers and a variety of cells.

• Dense connective tissue proteins form in thick bundles and fill nearly all the extracellular space.

• Dense regular connective tissue has protein fibers in the extracellular matric that are oriented predominantly in one direction.

• dense regular collagenous connective tissue has abundant collagen fibers

• difference b/w tendons and ligaments, collagen fibers of ligaments are less compact, some fibers of ligaments are not parallel, and ligaments usually are more flattened than tendons and form sheets or bands of tissues.

• dense reg elastic connective tissue consists of parallel bundles of collagen fibers and abundant elastic fibers

• dense irregular conn. tissue contians protein fibers arranged as a meshwork of randomly oriented fibers.

• dense irreg collagenous connective tissue forms most of dermis of skin, the tough inner potion of skin and of connective tissue caposules that surround organs such as kidney and spleen

• dense irreg elastic connective tissue is found in wall of elastic arteries. in addition to collagen fibers in many directions, there are abundant elastic fibers in the layers of this tissue,

  Reticular tissue

• forms the framework of lymphatic tissue such as in spleen and lymph nodes as well as in bone marrow and liver.

• reticular cells produce the reticular fibers and remain closely attached to them

  cartilage

• is composed of cartilage cells or chondrocytes located in spaces called lacunae

• within cartilage matrix, proteoglycan aggregates function as minute sponges capable of trapping large quantities of water which alllows cart to spring back after compressed

• the perichondrium is the surrounding layer of dense irregular connective tissue for the cartilage.

• hylaine cartilage has large amounts of both collagen fibers and proteoglycans

• cartilage has no blood vessels or nerves except those of the perichondrium

• fibrocart has more collagen fibers than proteoglycans. it also has much thicker bundles of collagen fibers dispersed through its matrix. very tough slighly compressible. found in areas of body where lot of pressure is applied to joints like knee and jaw.

• elastic cart had elastic fibers in addition to collafen and proteoglycans, found in ear

bone

• bone cells or osteocytes are located in lacunae that are surrounded by hydroxyapatite that make bone hard.

• cancellous bone has spaces between bony trabeculae, and compact bone is more solid

• blood cells are suspended in a fluid matrix

• hemopoietic tissue forms blood cells.

muscle tissue

• ability to contract

• sleketal muscle (striated voluntary) muscle attaches to bone and is responsible for movement of body.

• cardiac (striated invol) muscle cells are cylindrical branching cells with a single, central nucleous. cardiac muscle found in heart.

• smooth (nonstriated invol) muscle forms walls of hollow organs, the iris of the eye, its cells are spindle shaped with a single central nucleus.

  nervous tissue

• able to conduct electric impulses and is composed of neurons (conductive cells) and neuroglia (support cells)

• neurons have cell processes called dendrites and axons. the dendrites receive electric impulses and axons conduct them.

  membranes

• mucous membranes consists of epithel cells, their basement mem, the lamina propria, and sometimes smooth muscle cells. they line cavities that open to the outside and often contain mucuous glands

• serous membranes line cavities that do not open to the xterior and do not contain glands but do secrete serous fluid

• synovial membranes are formed by connective tissue and link joint cavities

  inflamation

• function of inflammatory response is to isolate injurious agents from the rest of the body and to attach and destroy the injurious agent

• the inflammatory response produces 5 symptoms, redness, heat, sweeling, pain, and disturbance of function.

  tissue repair

• substitution of viable cells for dead ones. Tissues repair occurs by regeneration or replacement

• labile cells divide throughout life and can undergo regeneration.

• stable cells do not orginarily divide after growth is complete, but can reginerate.

• permenant cells cannot replicate, but if killed it can be replaced.

• tissue repair by primary union occurs when the edges of the wound are close together. Secondary union occurs when stages are far apart.