Chapter 4 - Histology: Part 2
membrane-like structures
mucous and cutaneous membranes
smooth muscle cells
muscle cells that have myofilaments that are arranged as irregular bundles scattered randomly in the cytoplasm
Striated muscle cells
muscle cells that have striations (alternating light and dark bands) caused by the arrangement of the myofilaments that overlap in some areas and not in others
neurons
nerve generate, conduct and receive information in the form of electrical signals; mostly amitotic (do not undergo mitosis)
tissue repair
process of wound healing
neuroglial cells
provide physical support, insulation, and nutrients for neurons, including anchoring neurons and blood vessels in place, monitoring the composition of the ECF, increasing the rate of nerve impulse transmission and circulating the fluid surrounding the brain and spinal cord; mitotic
fibrosis
replacement of damaged or dead cells with fibroblasts that divide by mitosis and and produce collagen to fill in the defect left by injury; the tissue does not regain its ability to function fully
True membranes
serous and synovial membranes: do not open to the outside of the body
dendrite
short, highly branched extensions from nerve cells that receive messages from the axon and other neurons and bring impulses to the cell body
Bone
solid and strong, not active tissue
cartilage
strong connective tissue that supports the body and is softer and more flexible than bone; absorbs shock and is resistant to tension, compression and shearing forces
Obesity
the condition of excess adipose tissue in proportion to lean body mass
nerve impulses
the electrical signals carried by a nerve cell
axon
the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands
Mast cells
the largest of the cell types in connective tissue proper; immune system cells that have cytosolic inclusions (granules) containing inflammatory mediators.
Fibroblasts
the most abundant cell type in connective tissue that produces protein fibers, ground substance and other elements of ECM; a mature cell with the properties of an immature cell; active cells lie close to collagen as they continually produce collagen proteins
regeneration
the process by which damaged or dead cells are replaced with cells of the same type
nervous tissue
tissue that composes the brain, spinal cord and nerves and carries electrical messages back and forth between the brain and every other part of the body. Composition: neurons, neuroglial cells, ECM mostly made of ground substance with unique proteoglycans and very few protein fibers
synovial membranes
two, connective layers of tissue that line the cavities surrounding freely moving joints. the inner layer consists of synoviocytes (modified fibroblasts) and the external layer is generally a mixture of loose and dense irregular connective tissue
scar tissue
type of dense irregular connective tissue that results from fibrosis
smooth muscle tissue
type of involuntary muscle tissue made up of smooth muscle cells that are flattened with a single, central ovoid nucleus; most are linked by gap junctions in their plasma membrane; found in the wall of nearly every hollow organ, as well as the walls of blood vessels, the eyes, the skin and the ducts of certain glands
Other immune cells
various other immune system cells migrate in and out of different connective tissues, depending on the needs of the body at the time
Leukocytes
white blood cells which function in immunity
Most connective tissues heal by regeneration
Typically done by division of immature cells, except cartilage which has a limited capacity to divide so often heals by fibrosis
Excitable cells
cells that respond to electrical or chemical stimulation
platelets
cellular fragments that play a role in the blood clotting process
erthrocytes
red blood cells that bind and transport oxygen throughout the body
types of muscle tissue
skeletal, cardiac, smooth
Skeletal muscle tissue
type of voluntary muscle tissue found mostly attached to the skeleton Characteristics: long, thin, striated muscle cells (fibers) that are arranged parallel to one another Function: contract to move the body
Epithelial tissues typically undergo regeneration
undergo a great degree of stress, so they regenerate; Skin and digestive tract (stem cells) Live and blood vessels (mature cells)
composition of cartilage
-the ECM, which contains glycosaminoglycans, proteoglycans, collagen fibers and elastic fibers, is largely responsible for its properties -two major cell types: chondroblasts (immature cartilage) and -avascular (unusual among CT types)
Big Picture of Tissues in Organs
Complex Organs: Trachea 1. Dense irregular connective issue (outermost layer) 2. Smooth muscle 3. Hyaline cartilage 4. Loose connective tissue 5. Pseudostratified ciliated columna epithelium (inner rings) Simple Structure: Skeletal muscle 1. Skeletal muscle tissue 2. Dense irregular collagenous connective tissue
Elastic cartilage
Components: -chondrocytes, elastic fibers, ECM Function: -involved in producing and detecting sound (vibration of elastic fibers) Location: -ears -epiglottis of larynx
Dense regular elastic connective tissue
Composition: - parallel elastic fibers with randomly oriented collagen fibers, ground substance Function: -allows tissues to stretch and recoil Location: -large blood vessels -certain ligaments
Adipose connective tissue
Composition: -adipocytes, protein fibers Function: -warm, insulation -shock absorption, protection -major energy reserve in the body Location: -deep to the skin (subcutaneous) in characteristic areas (abdomen, breasts, buttocks, thighs) -surrounds the heart and other organs
Dense regular collagenous connective tissue
Composition: -fibroblasts, collagen fibers (arranged parallel to one another to form bundles), ground substance Function: -strength -resistance to stress in one plane Location: -tendons, ligaments
Dense irregular connective tissue
Composition: -fibroblasts, collagen fibers(primary type), ground substance Function: -strength -resistance to stress in all three planes Location: -deepest layer of skin -around joints, organs
Reticular connective tissue
Composition: -reticular fibers (produced by surrounding fibroblasts), leukocytes Function: -forms internal structure of many organs; web-like net of reticular fibers traps old and foreign cells and house white blood cells -supports smaller vessels and nerves Location: -lymph nodes, spleen, bone marrow, liver -basement membrane -around vessels and nerves
Perichondrium
Dense irregular connective tissue membrane covering cartilage that contains the blood supply for the cartilage; oxygen and nutrients must diffuse from the blood vessels through the ECM to reach the chondrocytes and chondroblasts
plasma
ECM of blood consisting of water, dissolved solutes and proteins (lacks protein fibers)
endomysium (external lamina)
ECM surrounding muscle cells that helps hold muscle cells in the tissue and blends with connective tissue around the muscle cells
Cells of connective tissue proper
Fibroblasts Adipocytes Mast cells Phagocytes Other immune cells
Types of connective tissue proper
Loose connective tissue Dense connective tissue Reticular tissue Adipose tissue
Myofilaments
The contractile proteins, actin and myosin, of muscle cells
intercalcated discs
The division between neighboring cardiac muscle cells. Intercalcated discs include gap junctions and modified tight junctions, which allow the cells to function as a unit and enable communication.
Connective tissues
a diverse group of tissues with a variety of functions: -connecting and binding (in and between organs) -support (bone and cartilage) -protection (bone and cartilage, immune system) -transport (blood)
mucous membrane (mucosa)
a membrane lining all body passages that open to the outside of the body, composed of a layer of epithelium, its basement membrane, lamina propria (a layer of loose connective tissue), and occasionally a thin layer of smooth muscle. Mucosae contain goblet cells that secrete mucus
serosae (serous membranes)
a single, thin sheet of tissue folded over on itself that consists of mesothelium (a layer of simple squamous epithelium), its basement membrane and a layer of loose connective tissue
serous fluid
a thin, watery fluid produced by mesothelial cells which fills the space between the parietal and visceral layers and provides lubrication so that organs can move without friction
cardiac muscle tissue
a type of involuntary, specialized muscle tissue found only in the heart Characteristics: short, thick, striated muscle cells that form branches and are often uninucleate cells are separated by intercalcated discs
synovial fluid
a watery, slippery fluid secrete by synoviocytes that lubricate joints
membrane function
anchor organs in place, serve as barriers, function in immunity, and secrete various substances
Osteoblasts
bone building cells that carry out the process of bone deposition; synthesize ECM, which they secrete by exocytosis, and produce the chemicals required for calcium salts to deposit within ECM Location: -outer surface of bone, close to periosteum (dense irregular collagenous connective tissue)
Specialized connective tissue
cartilage, bone (osseous), blood
Neurons generally do not regenerate
cells are unable to undergo mitosis; damaged neurons are usually replaced by neuroglial cells that divide to produce a scar; however, axons (outside brain and spinal cord) have the ability to regenerate depending on the location and nature of the damage
Skeletal and cardiac muscle tissues generally heal by fibrosis
cells cannot undergo mitosis, so typically heal by fibrosis although skeletal muscle tissue has satellite cells which allows a limited degree of regeneration
Smooth muscle tissue usually regenerates
cells largely retain ability to undergo mitosis so heal by regeneration
inflammatory mediators
chemicals substances that once triggered are released triggering inflammation which activates a response from the immune system
Loose (areolar) connective tissue
composed primarily of ground substance with all three types of protein fibers, fibroblasts and other cells such as adipocytes Function: -support -protection -houses blood vessels supplying epithelium Location: -Deep to epidermis -Walls of hollow organs -Membranes lining body cavities
Dense (fibrous) connective tissue
composed primarily of protein fibers
classes of connective tissue
connective (general) tissue proper and specialized connective tissues
Bone (osseous) tissue
connective tissue with the matrix hardened by calcium phosphate and other minerals Composition -65% inorganic materials (calcium phosphate) -35% organic materials (collagen fibers, osteoid(ground substance)) Functions: -support -protecting vital organs -storing calcium salts -housing bone marrow (tissue that produces blood cells and stores fat)
Connective tissue proper
connects tissues and organs to one another and forms part of the internal structure of some organs
Fibrocartilage
dominated by bundles of collagen fibers Components: -chondrocytes, fibroblasts, collagen fibers, ECM Function: -support -protection -resists compression Location: -fibrous joints -intervertebral discs
myocytes (muscle cells)
excitables cells with cytoplasm filled with myofilaments
Adipocytes
fat cells; most are dominated by a single large inclusion of lipids and the nucleus and other organelles are squashed to the perimeter and difficult to see in sections
Blood
fluid connective tissue of the circulatory system; consists of blood cells and plasma
Bone remodeling
healthy bone constantly undergoes the processes of bone deposition and bone resorption; both can occur simultaneously in different areas tension => increased osteoblast activity and bone deposition pressure => increased osteoclast activity and bone resorption
stem cells
immature cells that renew themselves and have the potential to develop into mature cells
Phagocytes
immune cells that can ingest foreign substances, microorganisms, and dead and damaged cells; two common types are macrophages (resident or migrant) and neutrophils (migrant)
Hyaline cartilage
large amount of ground substance gives uniform, glassy appearance; fetal skeletons start as mostly hyaline cartilage before becoming bone Components: -chondrocytes, bundles of fine collagen fibers, ECM Function: -support -protection -resists compression Location: -between bones in joints (articular cartilage) -between sternum and ribs -nose -respiratory tract
Soma (cell body)
large, centralized portion of the neuron that is the biosynthetic center, where the nucleus and most other organelles are housed
Osteoclasts
large, multinucleated cells that destroy bones; carry out the process of bone resorption, during which they secrete hydrogen ions and enzymes that catalyze reactions to break down the components of ECM
cutaneous membrane (skin)
largest organ of the body; epidermis (outer layer of keratinized stratified squamous epithelium) and dermis (a layer of loose connective tissue and an even deeper layer of dense irregular connective tissue)
Muscle fibers
long, slender cells that make up muscles, formed by the fusion of embryonic myoblasts retained within mature muscle fibers, causing it to be multinucleate; the nuclei are located near the outer edge of the fiber and aid in function as muscles requires near constant synthesis of enzymes, structural proteins and contractile proteins
Composition of connective tissue
loosely packed cells surrounded by protein fibers, all of which are embedded in ground substance
Osteocytes
mature bone cells found in lacunae; they produce substances required for bone maintenance (exocytosis)
chondrocytes
mature cartilage cells found in lacunae (small cavities in ECM)
