Anatomy: Chap 4 Tissues

A significant structural feature in the microscopic study of cardiac muscle cells is the presence of gap junctions between neighboring cells. Why are these junctions so important?

"Intercalated discs" are strong gap junctions between cardiac cells that promote rapid transport of electrical stimuli through many cardiac muscle cells at once, allowing the entire muscle wall to contract at a unit.

Describe the primary component of the matrix found in bone.

1/3 organic components (collagen fibers & protein/carb molecules) 2/3 inorganic components (calcium salts, primarily calcium phosphate)

Goblet cell

A single-celled gland that secretes mucin. Found in columnar epithelium.

Which cell types are found in Areolar CT? Why is this the ideal environment to fight infection?

All CTP cells: Fibroblasts, adipocytes, macrophages, mast cells, plasma cells. Fibers are loosely distributed, allowing for greater cell movement.

Lesion

Any localized wound, injury, or infection that affects tissue over a specific area rather than spread throughout the body.

How does the fact that cartilage is avascular affect its ability to heal?

Blood carries nutrients necessary for healing. In cartilage, these must arrive through diffusion from nearby blood vessels.

Why is blood considered to be a connective tissue? What are the formed elements of blood?

Blood has the same component parts as other connective tissue: cells, ground substance, and protein fibers. The formed elements are erythrocytes (RBC), leukocytes (WBC), and platelets.

What type of tissue contains a calcified ground substance and is specialized for structural support?

Bone connective tissue

Where might you find reticular connective tissues in the body?

Bone marrow, stroma of many lymphatic organs: spleen, thymus, lymph nodes.

Distinguish between the parietal and visceral layers of the serous membrane.

Both layers are serous membranes, composed of a simple squamous epithelium and a thin underlying layer of loose connective tissue. The parietal layer lines the body cavity, while the visceral layer covers the individual organs. They are in close contact with a thin layer of serous fluid (derived from plasma) between.

Which connective tissue type is composed of cells called chondrocytes and may be surrounded by a covering called perichondrium?

Cartilage

What are common characteristics of all epithelium?

Cellularity (composed almost entirely of cells) Polarity (there's a clear top and bottom) Attachment (bound to the basal membrane) Avascularity (no blood vessels, nutrients etc derived through diffusion) Innervation (nerve tissues mostly in connective tissue layer) High regeneration capacity (deepest epithelial cells are stem cells)

Describe the composition of cartilage. What structural advantages does it have over tendon/ligament? Over bone?

Chondrocytes, many protein fibers, and a semi-solid ground substance. It is stronger than tendons/ligaments, and not as brittle as bone.

Identify the three types of protein fibers in connective tissue proper.

Collagen fibers (collagen) Elastic fibers (elastin) Reticular fibers (collagen subunits combined differently, coated with a glycoprotein)

Why is collagen the most abundant fiber type in tendons and ligaments?

Collagen has the highest tensil strength of the protein fibers and is therefore used in areas that undergo the greatest stress. Tendons and ligaments generally undergo stress in only one direction, therefore the fibers are oriented in the same direction.

What three categories are used to classify connective tissue types?

Connective tissue proper: Areolar, adipose, reticular, dense regular, dense irregular, elastic Supporting connective tissue: Bone & cartilage Fluid connective tissue: Blood

What type of body membrane is found on the external surface of your forearm?

Cutaneous membrane, composed of keratonized stratified squamous epithelium (epidermis) and a layer of connective tissue (dermis).

What is an osteon?

Cylindrical structures (running parallel to the shaft of long bones) that make up the calcified matrix. They contain concentric rings of bone (lamellae), which encircle a central canal.

What type of connective tissue have you damaged when you sprain your ankle? Why does it take so long to heal?

Dense regular connective tissue makes up tendons and ligaments, where stress is normally applied in one direction. It has few blood vessels. Because a rich blood supply is necessary for healing, injuries take a long time to heal.

What is the predominant cell type in areolar connective tissue?

Fibroblast

From a structural perspective, which CTP cells are the most important?

Fibroblasts as the synthesize the fibers that create CTP structure

Name the 6 cell types found in connective tissue proper and briefly describe the functions of each.

Fibroblasts: Predominant cell of CTP. Synthesis of fibers and ground substance. Adipocytes: Can be dispersed or concentrated in CTP. Fat storage. Macrophages (fixed & wandering): Phagocytic cells Mast cells: wandering cells that mediate inflammation Plasma cells: source of circulating antibodies.

What general name is applied to the supporting cells in nervous tissue?

Glial cells

What are the main components of the extracellular matrix?

Ground substance and protein fibers

The study of tissues is called __________ .

Histology

Why is epithelial cell regeneration important to the continued functioning of a holocrine gland?

Holocrine glands accumulate their secretion within each cell. The secretion is released when the cell ruptures. Each cell is therefore only useful once. Without regeneration, the gland would soon cease to function.

In what region of the body would you expect to find hyaline cartilage, fibrocartilage, and elastic cartilage? Why would these supporting connective tissues be located in these regions?

Hyaline cartilage: Fetal skeleton, articular ends of long bones, larynx, trachea, nose. Found here because it provides a smooth surface for joint movement, it is a model for bone growth, and it supports soft tissue. Fibrocartilage: Intervertebral discs, pubic symphysis, menisci of knee. Found here because it resists compression and absorbs shock well. Elastic cartilage: External ear, epiglottis of the larynx. Found here because it is particularly flexible while maintaining its structure. These areas receive more multi-directional pressure.

Adhesions

Inflammatory bands that connect opposing serous surfaces

Smooth Muscle

Involuntary, striated muscle tissue. Involved in bodily functions like blood vessel constriction, stomach, intestinal & bladder lining.

Why is plasma akin to the matrix of other connective tissue types?

It also contains a ground substance and protein fibers. In this case, the fibers are dissolved until they are needed for clotting.

Why is smooth muscle referred to as involuntary?

It is not controlled by the nervous system and we do not have control over their function.

What types of ephithelium are well suited for protection?

Keratonized stratified squamous epithelium are the best suited for protection. Non-keratonized stratified squamous epithelium are the next best protection.

What are some aging effects on tissue?

Less able to maintain itself Decreased ability to repair Thinning epithelium Connective tissues lose pliability & resilience The amount of collagen in the body declines

What is the function of mucous membranes

Lines body passageways and compartments that eventually open to the external environment. They perform absorptive, protective, and secretory functions. They prevent underlying cells from drying out, provides lubrication, and traps bacteria and foreign particles to prevent them from invading the body.

Compare loose to dense connective tissue with respect to fiber density and distribution and amount of ground substance.

Loose Connective Tissue has more ground substance and lower proportion of protein fibers than Dense CT. It is found surrounding nerves/vessels/kidneys/some other organs, supporting epithelia, and in the stroma of the spleen/liver/lymph nodes/bone marrow. Dense Connective Tissue is sometimes called collagenous tissue because collagen is the dominant fiber type. It makes up ligaments, tendons, dermis, and surrounds some organs and the walls of large arteries.

What distinguishes loose from dense connective tissue?

Loose Connective Tissue has more ground substance and lower proportion of protein fibers than Dense CT. It is found surrounding nerves/vessels/kidneys/some other organs, supporting epithelia, and in the stroma of the spleen/liver/lymph nodes/bone marrow. Dense Connective Tissue is sometimes called collagenous tissue because collagen is the dominant fiber type. It makes up ligaments, tendons, dermis, and surrounds some organs and the walls of large arteries.

What is the name for a mature bone cell? An immature cell? What is an osteoclast?

Mature BC: Osteocyte Immature BC: Osteoblast Osteoclast: a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone

What are the three secretion methods of exocrine glands? How does each work?

Merocrine Gland: package secretions in secretory vesicles, which travel to the apical surface of the cell and release contents through exocytosis. (tear, salivary, sweat, stomach gastric glands) Holocrine Gland: more viscous secretions accumulate within each cell. The secretions are released with the cell ruptures. (sebaceous glands) Apocrine Gland: secretions accumulate in the apical portion of the cytoplasm. Products are secreted when the apical portion pinches off. (mammary, ceruminous/earwax glands)

A gland that releases its secretions by exocytosis into secretory vesicles is called a ___ gland.

Merocrine gland

Biopsy

Microscopic examination of tissue removed from the body for the purpose of diagnosing disease.

Preventing desiccation and providing surface lubrication within a body cavity are the functions of ____ membranes.

Mucous

Name the four types of body membranes, and cite a location for each.

Mucous: Lines the digestive, respiratory, reproductive, and urinary tracts. Serous: Lining the friction locations between body cavities and organs and between various organs themselves. Cutaneous: Covering the body as skin. Synovial: Lining some joints.

What is the extracellular matrix?

Nonliving material produced by the connective tissue cells. It can be viscous (blood), semisolid (cartilage) or solid (bone).

What is the role of the perichondrium and periostium?

Perichondrium:vDense, irregular CT covering cartilage. Periostium: Dense, irregular CT covering bones.

Merocrine Secretion

Products of merocrine glands are secreted though the plasma membrane in vesicles via exocytosis.

Which epithelial tissue type lines the trachea?

Pseudostratified ciliated columnar epithelium

What are the main structural differences between dense regular and dense irregular connective tissue?

Regular Dense Connective Tissue: collagen fibers are dense and parallel. Used for tendons, ligaments that have stress applied in one direction under normal use. Irregular Dense Connective Tissue: collagen fibers are randomly arranged and clumped. There is more ground substance than RDCT. Withstands stresses in all directions. Used in dermis, covers cartilage/organ capsules.

endothelium

Simple, squamous epithelium lining the lumen of the blood and lymphatic vessels, the heart, and the heart's chambers.

What type of muscle tissue has long, cylindrical, multi-nucleated cells with obvious striations?

Skeletal muscle tissue

What are the similarities and differences between skeletal muscle, cardiac muscle, and smooth muscle?

Smooth muscle: involuntary, non-striated, single nucleus Cardiac muscle: involuntary, striated, single or double nuclei Skeletal muscle: voluntary, striated, multi-nucleated, with nuclei at the periphery

What are the origins of the basement membrane?

The LL and LD contain collagen fibers as well as proteins and carbs, some of which are secreted by the epithelial cells. The RL is secreted by the underlying connective tissue layer.

Describe the basement membrane, its origins, and its functions.

The basement membrane is seen as a single layer beneath the epithelium. It consists of three layers: the lamina lucida, the lamina densa, and the reticular lamina.

What type of intercellular junction provides resistance to mechanical stress at a single point?

The desmosome, or macula adherens "adhering spot".

What are the two basic parts of a multicellular exocrine gland?

The duct and the secretory portion make up the two main parts.

What are the functions of the basement membrane?

The functions are to: * Provide physical support for the epithelium * Anchor the epithelium to the connective tissue * Act as a barrier to regulate the movement of large molecules between epithelium and the underlying connective tissue

What are gap junctions in epithelial cells?

The intercellular gap is bridged by "connexons", rings of six transmembrane proteins creating a pore. It is a direct passageway for small molecules: ions, glucose, amino acids and other small solutes.

Why is one epithelium referred to as "pseudostratified"?

The nuclei are at different levels within the tissue, even though all cells in the layer are connected to the basement membrane. Note: not all apical ends reach the surface. these cells are protected and function as stem cells.

What two main characteristics are used to classify epithelial tissues?

The number of layers: single vs. stratified (2+) The apical cell shape: squamous, cuboid, columnar

Why does connective tissue contain fewer cells than epithelium?

The primary function of connective tissue is support, protection and binding. To achieve this, it requires a large amount of protein fiber. Cells must therefore make up a smaller proportion of the overall content of the tissue. Motile cells are more useful here for distributing nutrients, removing wastes, and healing damaged tissue.

cardiac muscle

The thick middle layer of the heart wall, called the myocardium.

Describe the types of intercellular junctions between epithelial cells and where each is located.

Tight Junctions: An occluding belt of fused plasma membrane proteins at the apical end of the lateral sides of each cell. Adhering Junctions: A strengthening and supporting belt surrounding the interior of each cell, just deep to the tight junction. Desmosomes: Discrete binding sites between cells at potential stress points. Binding is achieved through protein filament webs extending through a protein plaque on the plasma membrane and extending into the cytoplasm. Gap Junctions: Connexons bridge the intercellular gap. Each connexons consists of 6 transmembrane proteins, arranged in a circular fashion to form a pore. Ions, glucose, amino acids and other small solutes pass through the pores.

What consistency does the ground substance have in areolar tissue? What chemical increases the viscosity of this ground substance?

Viscous. Hyaluronic acid

Name a few sites in the body where elastic connective tissues would be of service.

Vocal cords, suspension of the penis, spinal column ligaments in the neck, large and medium arteries.

What type of cartilage is found in each of the following locations: a) external ear b) pubic symphysis c) costal cartilage d) epiglottis e) articular surface of a long bone f) intervertebral disk.

a) Elastic b) Fibrocartilage c) Hyaline d) Elastic e) Hyaline f) Fibrocartilage

List the epithelial type that is found a) lining the lumen of the stomach b) lining the oral cavity c) lining the urinary bladder d) lining the tiny air sacs of the lung

a) simple columnar (no goblet cells) b) non-keratinized stratified squamous c) transitional (stratified) d) simple squamous

What characteristics are common to all connective tissues?

cells, protein fibers, and ground substance

Which muscle type consists of long, cylindrical, striated cells with multiple nuclei located at the periphery of the cell?

skeletal muscle

Which intercellular junction ensures that epithelial cells act as "gatekeepers"?

tight junctions, because they create a fused barrier connecting all sides of each cell