A&P CH 4 TISSUES
What role do desmosomes play in the skin?
Among the glycoprotein connections between cells, there are some relatively strong adhesive structures called desmosomes. Desmosomes consist of adhesive glycoproteins that bind cells together and intracellular proteins attached to intermediate filaments that extend into the cytoplasm of the cells. Many desmosomes are found in epithelial tissues that are subjected to stress, such as the stratified squamous epithelium of the skin. Hemidesmosomes, similar to one-half of a desmosome, attach epithelial cells to the basement membrane.
Compare the structure of skeletal, cardiac, and smooth muscle cells.
Cardiac muscle is under involuntary (unconscious) control, although a person can learn to influence the heart rate by using techniques such as meditation and biofeedback. Cardiac muscle cells are cylindrical but much shorter than skeletal muscle cells. Cardiac muscle cells are striated and usually have one nucleus per cell. They are often branched and connected to one another by intercalated (in-ter′kă-lā-ted; inserted between) disks, which contain specialized gap junctions and are important in coordinating cardiac muscle cell contractions.
What are the three functions that cell stuctures do to hold themselves to one another?
Cells have structures that hold them to one another or to the basement membrane. These structures do three things: (1) mechanically bind the cells together, (2) help form a permeability barrier, and (3) provide a mechanism for intercellular communication.
Name the possible ways by which epithelial cells are bound to one another and to the basement membrane.
Epithelial cells have cell surface glycoproteins, which attach to other glycoproteins located on adjacent cells and in the basement membrane.
Distinguish between exocrine and endocrine glands.
Glands with ducts are called exocrine (ek′sō-krin) glands----some glands become separated from the epithelium of their origin and have no ducts; these are called endocrine (en′dō-krin) glands.
What are the functions of glia?
Glia (g′lē-ă; glue) are the support cells of the brain, spinal cord, and peripheral nerves. Glia nourish, protect, and insulate neurons.
What is an adipocyte? .
adipocytes, which contain large amounts of lipid. fat cell.
What does mesenchyme give rise to in the adult?
all adult connective tissue types develop from it
How do cells respond to the effects of aging?
cells divide more slowly in older people. Collagen fibers become more irregular in structure, even though their number may increase. A
What type of connective tissue is found in tendons and ligaments?
dense regular collagenous tissue
Describe the basement membrane
made of COLLAGEN and GLYCOPROTEINS & attaches epithelium to connective tissue underneath. (divides one tissue from another)
Which type of muscle is under voluntary control?
skeletal muscle
Where is each type of muscle tissue found, and what tasks does each perform?
skeletal: attached to bone or other connective tissues, like the arms, etc. cardiac muscle: pumps the heart and is involuntary. smooth muscle: in hollow organs like small and large intestine, iris of the eyes, etc. produces goose bumps, controls light entering eyes, moves fluis and foods through tubes.
Give an example of a unicellular exocrine gland. What does it secrete?
some exocrine glands are composed of a single cell and are called unicellular glands. For example, goblet cells are unicellular glands that secrete mucus.
Explain the differences among -blast, -cyte, and -clast cells of connective tissue.
the specialized cells of the various connective tissues produce the extracellular matrix. The name of the cell identifies the cell functions by means of one of the following suffixes: -blast, -cyte, or -clast. Blasts create the matrix, cytes maintain it, and clasts break it down for remodeling. -Osteoblasts form bone (osteo-, bone), osteocytes maintain it, and osteoclasts break it down (see chapter 6). Fibroblasts are cells that form fibrous connective tissue, and fibrocytes maintain it. Chondroblasts form cartilage (chondro-, cartilage), and chondrocytes maintain it.
List the two types of embryonic tissue.
--Mesenchyme and mucous connective tissue. It is composed of fibroblasts surrounded by semifluid extracellular matrix containing delicate reticular fibers --The major source of remaining embryonic connective tissue in the newborn is in the umbilical cord, where it is called mucous connective tissue, or Wharton's jelly. The mucous connective tissue helps support the umbilical cord blood vessels between the mother and the child. After birth, the mucous connective tissue can also be a rich source of stem cells.
Distinguish among squamous, cuboidal, and columnar epithelial cells.
-Squamous cells are flat or scalelike. -Cuboidal (cubelike) cells are cube-shaped about as wide as they are tall. -Columnar (tall and thin, similar to a column) cells tend to be taller than they are wide.
What are the three components of the extracellular matrix of connective tissue?
1) protein fibers:3 types; collagen, reticular, and elastic—help form connective tissue. (2) ground substance, and (3) fluid
What is the main characteristic that distinguishes connective tissue from other tissues?
Connective tissue differs from the other three tissue types in that it consists of cells separated from each other by abundant extracellular matrix. Connective tissue is diverse in both structure and function.
A stratified layer?
The multiple layers of cells in stratified epithelium are well adapted for a protective role. As the outer cells are damaged, they are replaced by cells from deeper layers; thus, a continuous barrier of epithelial cells is maintained in the tissue. Stratified squamous epithelium is found in areas of the body where abrasion can occur, such as the skin, mouth, throat, esophagus, anus, and vagina.
Where can motile cilia be found? What are their functions?
motile cilia contain microtubules, which allow them to move materials across the free surface of the cell . Three types of ciliated epithelium line the respiratory tract, where cilia move mucus containing foreign particles out of the respiratory airways. Cilia are also found on the apical surface of the simple columnar epithelial cells of the uterus and uterine tubes, where the cilia help move mucus and oocytes.
Compare labile, stable, and permanent cells according to their ability to regenerate. Give examples of each type.
1. Labile cells continue to divide throughout life. Labile cells include adult stem cells and other cells of the skin, mucous membranes, and hemopoietic and lymphatic tissues. Damage to these cells can be repaired completely by regeneration. 2. Stable cells, such as those of connective tissues and glands, including the liver, pancreas, and endocrine glands, do not normally divide after growth ceases, but they retain the ability to divide and are capable of regeneration in response to injury. 3. Permanent cells have a very limited ability to replicate and, if killed, are usually replaced by a different type of cell. Some permanent cells, such as neurons, are postmitotic. If damaged, neurons may recover if the cell body is not destroyed; however, if the neuron cell body is destroyed, the remainder of the neuron dies ome undifferentiated cells of the central nervous system are stem cells that can undergo mitosis and form functional neurons in the adult. This has raised hope that damaged areas of the brain may be regenerated.
What is the general function of gap junctions?
A gap junction is a 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. In epithelium, the function of gap junctions is not entirely clear; gap junctions between ciliated epithelial cells may coordinate the movements of cilia. In cardiac and smooth muscle tissues, gap junctions are important in coordinating important functions. Because ions can pass through the gap junctions from one cell to the next, electrical signals can pass from cell to cell to coordinate the contraction of cardiac and smooth muscle cells. Thus, electrical signals that originate in one cell of the heart can spread from cell to cell and cause the entire heart to contract. In the heart, the gap junctions between cardiac muscle cells are found in specialized cell-to-cell connections called intercalated disks. Intercalated disks contain both gap junctions and desmosomes that help hold adjacent cells in close contact.
Describe the mucous membrane and its functions
A mucous (mū′kŭs) membrane lines cavities and canals that open to the outside of the body, such as the digestive, respiratory, excretory, and reproductive passages. Mucous membranes consist of epithelial cells, their basement membrane, and a thick layer of loose connective tissue called the lamina propria --- The functions of the mucous membranes vary, depending on their location, and include protection, absorption, and secretion. For example, the stratified squamous epithelium of the oral cavity performs a protective function, whereas the simple columnar epithelium of the small intestine absorbs nutrients and secretes digestive enzymes and mu
Define and list the functions of the cell body, dendrites, and axon of a neuron.
A neuron is composed of three major parts: a CELL BODY, : contains the nucleus and is the site of general cell functions DENDRITESs, :Dendrites and axons consist of projections of cytoplasm surrounded by membrane. Dendrites (den′drītz) usually receive action potentials. They are much shorter than axons and have multiple branches at their ends --AXON:The axon (ak′son) usually conducts action potentials away from the cell body. Axons can be much longer than dendrites, and they have a constant diameter along their entire length..
Why does cartilage heal slowly?
Cartilage has no blood vessels or nerves, except those of the perichondrium; it therefore heals very slowly after an injury because the cells and nutrients necessary for tissue repair cannot reach the damaged area easily.
Describe the age-related changes in tissues with abundant collagen and elastic fibers.
A s a consequence, connective tissues with abundant collagen, such as tendons and ligaments, become less flexible and more fragile. Elastic fibers fragment, bind to calcium ions, and become less elastic. Consequently, elastic connective tissues become less elastic. Reduced flexibility and elasticity of connective tissue are responsible for increased wrinkling of the skin, as well as the increased tendency for bones to break in older people.
What is the serous membrane and its functions?
A serous (sēr′ŭs) membrane lines cavities that do not open to the exterior of the body, such as the pericardial, pleural, and peritoneal cavities. Serous membranes consist of three components: a layer of simple squamous epithelium called mesothelium, its basement membrane, and a delicate layer of loose connective tissue. Serous membranes do not contain glands, but they secrete a small amount of fluid called serous fluid, which lubricates the serous membranes, making their surfaces slippery. Serous membranes protect the internal organs from friction, help hold them in place, and act as selectively permeable barriers to prevent large amounts of fluid from accumulating within the serous cavities.
What are the four tissue membranes in the body?
A tissue membrane is a thin sheet of tissue that covers a structure or lines a cavity. Most membranes are formed from a superficial epithelial tissue and the connective tissue on which it rests. There are four tissue membranes in the body, one external and three internal. The external membrane is the skin, or cutaneous membrane (see chapter 5). The three major categories of internal membranes are mucous, serous, and synovial membranes.
What is the function of adhesive molecules? Give some specific examples.
Adhesive molecules in the ground substance hold the proteoglycan aggregates together, as well as attach them to cells of the tissue. Specific adhesive molecules predominate in certain types of ground substance. For example, 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 tissue.
Name the two types of adipose tissue, and give the functions of each. Which type is primarily found in infants?
Adipose tissue exists in both yellow and brown forms. Yellow adipose tissue is by far the most abundant. --In humans, brown adipose tissue is found in specific areas of the body, such as the axillae (armpits), the neck, and near the kidneys. The brown color results from the cytochrome pigments in the tissue's numerous mitochondria and its abundant blood supply. --- Brown adipose tissue is specialized to generate heat as a result of oxidative metabolism of lipid molecules in mitochondria. It can play a significant role in regulating body temperature in newborns and is now recognized to also play a role in adult metabolism
What are the three classifications of adult connective tissue, and what tissue types are included in each?
Adult connective tissue consists of three types: ----connective tissue proper (loose and dense) -areolar -adipose -reticular ----supporting connective tissue (cartilage and bone), -dense regular colagenous tissue (tendons attach muscle to bone, ligaments attach bone to bone) -dense regular elastic connective tissue (vocal folds, elastic ligaments btwen vert. -dense irregular collagenous tissue- (most dermis of the skin, sheaths, etc) -dense irregular elastic connective tissue (elastic arteries) ---and fluid connective tissue (blood).
Name the three embryonic germ layers.
Approximately 13 or 14 days after fertilization, the embryonic stem cells that give rise to a new individual form a slightly elongated disk consisting of two layers, the epiblast and the hypoblast (the suffix -blast means bud or germ). Cells of the epiblast then migrate between the two layers to form the three embryonic germ layers: the ectoderm, the mesoderm, and the endoderm. The ectoderm, mesoderm, and endoderm are called germ layers because the beginning of all adult structures can be traced back to one of them. The germ layers give rise to all the tissues of the body
Describe the fiber arrangement in loose (areolar) connective tissue. What are the functions of this tissue type, and where is it found in the body?
Areolar (ă-r ē′ō-lăr) tissue is the "loose packing" material of most organs and other tissues; it attaches the skin to underlying tissues. It contains collagen, reticular, and elastic fibers and a variety of cells. For example, fibroblasts produce the fibrous matrix; macrophages move through the tissue, engulfing bacteria and cell debris; mast cells contain chemicals that help mediate inflammation; and lymphocytes are involved in immunity. The loose packing of areolar tissue is often associated with the other loose connective tissue types, adipose and reticular tissue.
What characteristic separates blood from other connective tissues?
Blood is unusual among the connective tissues because the matrix between the cells is liquid. blood cells move freely within a fluid matrix. Blood's liquid matrix allows it to flow rapidly through the body, page 125carrying nutrients, oxygen, waste products, and other materials. The matrix of blood is also unusual in that most of it is produced by cells contained in other tissues, rather than by blood cells.
Describe the cells and matrix of bone.
Bone is a hard connective tissue that consists of living cells and mineralized matrix. Bone matrix has organic and inorganic portions. The organic portion consists of protein fibers, primarily collagen, and other organic molecules. The mineral, or inorganic, portion consists of specialized crystals called hydroxyapatite (hī-drok′sē-ap-ă-tīt), which contains calcium and phosphate. The strength and page 124 rigidity of the mineralized matrix allow bones to support and protect other tissues and organs. Osteocytes (os′tē-ō-sītz), or bone cells, are located within holes in the matrix, which are called lacunae and are similar to the lacunae of cartilage.
Contrast the structure and characteristics of collagen fibers, reticular fibers, and elastic fibers.
COLLAGEN FIBERS: Collagen is synthesized within fibroblasts and secreted into the extracellular space. After collagen molecules are secreted, they are linked together to make long collagen fibrils. The collagen fibrils are then joined together in bundles to form collagen fibers (figure 4.5a). Collagen fibers are very strong and flexible, like microscopic ropes, but are not very elastic. There are at least 20 types of collagen fibers, many of which are specific to certain tissues. RETICULAR FIBERS: Reticular (re-tik′ū-lār; netlike) fibers are very fine collagen fibers and therefore not a chemically distinct category of fibers. However, reticular fibers are very different from collagen fibers. They are not as strong as most collagen fibers. They are very short, thin fibers that branch to form a network. Networks of reticular fibers fill spaces between tissues and organs. ELASTIC FIBERS: Elastic fibers consist of the protein elastin (e-las′tin). As the name suggests, this protein has the ability to return to its original shape after being stretched or compressed, giving tissue an elastic quality. Fibroblasts secrete elastin polypeptide chains, which are linked together to form a network. The elastin network stretches like a rubber band in response to force and recoils when relaxed (figure 4.5b). Elastic fibers provide the elasticity of skin, lungs, and arteries.
Describe cardiac muscle.
Cardiac muscle is under involuntary (unconscious) control, although a person can learn to influence the heart rate by using techniques such as meditation and biofeedback. Cardiac muscle cells are cylindrical but much shorter than skeletal muscle cells. Cardiac muscle cells are striated and usually have one nucleus per cell. They are often branched and connected to one another by intercalated (in-ter′kă-lā-ted; inserted between) disks, which contain specialized gap junctions and are important in coordinating cardiac muscle cell contractions.
Describe the cells and matrix of cartilage.
Cartilage (kar′ti-lij) is composed of cartilage cells within an extensive and relatively rigid matrix. The surface of nearly all cartilage is surrounded by a layer of dense irregular connective tissue called the perichondrium (per-i-kon′drē-ŭm), described in more detail in chapter 6. Cartilage cells arise from the perichondrium and secrete cartilage matrix. Once completely surrounded by matrix, the cartilage cells are called chondrocytes (kon′drō-sītz), and the spaces in which they are located are called lacunae (lă-koo′nē). The matrix contains protein fibers, ground substance, and fluid. The protein fibers are collagen fibers or a mixture of collagen and elastic fibers. Within the cartilage matrix, proteoglycan aggregates function as minute sponges capable of trapping large quantities of water. This trapped water allows cartilage to spring back after being compressed. The collagen fibers give cartilage considerable strength. Next to bone, cartilage is the firmest structure in the body.
What are lacunae? What is the perichondrium?
Cartilage (kar′ti-lij) is composed of cartilage cells within an extensive and relatively rigid matrix. The surface of nearly all cartilage is surrounded by a layer of dense irregular connective tissue called the perichondrium (per-i-kon′drē-ŭm), described in more detail in chapter 6. Cartilage cells arise from the perichondrium and secrete cartilage matrix. Once completely surrounded by matrix, the cartilage cells are called chondrocytes (kon′drō-sītz), and the spaces in which they are located are called lacunae (lă-koo′nē). The matrix contains protein fibers, ground substance, and fluid. The protein fibers are collagen fibers or a mixture of collagen and elastic fibers. Within the cartilage matrix, proteoglycan aggregates function as minute sponges capable of trapping large quantities of water. This trapped water allows cartilage to spring back after being compressed. The collagen fibers give cartilage considerable strength. Next to bone, cartilage is the firmest structure in the body.
Why are cuboidal or columnar cells found where secretion or absorption is occurring?
Cells that secrete or absorb are usually cuboidal or columnar. They have greater cytoplasmic volume relative to surface area than seen with squamous cells. This greater volume results from the presence of organelles responsible for the tissues' functions. For example, pseudostratified columnar epithelium, which secretes large amounts of mucus, lines the respiratory tract and contains large goblet cells, which are specialized columnar epithelial cells. The goblet cells are responsible for synthesizing and secreting mucus.
Name the two kinds of dense regular connective tissue, and give an example of each. Do the same for dense irregular connective tissue
Dense regular and dense elastic connective tissue. Tendons and ligaments are dense regular connective tissues. Vocal cords and nuchal ligament (that helps hold the head up right, in the back of the neck) are regular elastic connective tissue. -Dense irregular collagenous connective tissue forms most of the dermis, which is the tough, inner portion of the skin, as well as the connective tissue capsules that surround organs such as the kidney and spleen. -Dense irregular elastic connective tissue is found in the walls of elastic arteries. In addition to collagen fibers, oriented in many directions, the layers of this tissue contain abundant elastic fibers.
What are the distinct cell surfaces found in epithelial tissue? Describe them.
Distinct cell surfaces. Most epithelial tissues have one free, or apical, surface where cells are exposed and not attached to other cells. The cells have a lateral surface where cells are attached to other epithelial cells. At the base of the cells is basal surface attached to a basement membrane. The free surface often lines the lumen of ducts, vessels, and cavities. The basement membrane is a specialized type of extracellular material secreted by epithelial and connective tissue cells. The basement membrane helps attach the epithelial cells to the underlying tissues, like the adhesive on ScotchTM tape. It plays an important role in supporting and guiding cell migration during tissue repair. The basement membrane is typically porous, which allows substances to move to and from the epithelial tissue above it. A few epithelial tissues, such as those in lymphatic capillaries and liver sinusoids, do not have basement membranes, and some epithelial tissues, such as those in some endocrine glands, do not have a free surface or a basal surface with a basement membrane.
List six characteristics common to most types of epithelial tissue.
Epithelial tissue, or epithelium, covers and protects surfaces, both outside and inside the body. 1. Mostly composed of cells. Epithelial tissue consists almost entirely of cells, with very little extracellular matrix between them. 2.Covers body surfaces. Epithelial tissue covers body surfaces and forms glands that are derived developmentally from body surfaces. The body surfaces include the exterior surface, the lining of the digestive and respiratory tracts, the heart and blood vessels, and the linings of many body cavities. 3.Distinct cell surfaces. Most epithelial tissues have one free, or apical, surface where cells are exposed and not attached to other cells. The cells have a lateral surface where cells are attached to other epithelial cells. At the base of the cells is basal surface attached to a basement membrane. The free surface often lines the lumen of ducts, vessels, and cavities. The basement membrane is a specialized type of extracellular material secreted by epithelial and connective tissue cells. The basement membrane helps attach the epithelial cells to the underlying tissues, like the adhesive on ScotchTM tape. It plays an important role in supporting and guiding cell migration during tissue repair. The basement membrane is typically porous, which allows substances to move to and from the epithelial tissue above it. A few epithelial tissues, such as those in lymphatic capillaries and liver sinusoids, do not have basement membranes, and some epithelial tissues, such as those in some endocrine glands, do not have a free surface or a basal surface with a basement membrane. 4. Cell and matrix connections. Specialized cell contacts bind adjacent epithelial cells together and to the extracellular matrix of the basement membrane. 5. Nonvascular. Blood vessels in the underlying connective tissue do not penetrate the basement membrane to reach the epithelium; thus, all gases and nutrients carried in the blood must reach the epithelium by diffusing from blood vessels across the basement membrane. In epithelial tissues with many layers of cells, diffusion must also occur across cells, and the most metabolically active cells are close to the basement membrane. 6. Capable of regeneration. Epithelial tissue has the ability to replace damaged cells with new epithelial cells. Undifferentiated cells (stem cells) continuously divide and produce new cells. In some types of epithelial tissues, such as those in the skin and the digestive tract, new cells continuously replace cells that die.
What are the cells of the connective tissue and their functions?
Fibroblasts are cells that form fibrous connective tissue, and fibrocytes maintain it. --Chondroblasts form cartilage (chondro-, cartilage), and chondrocytes maintain it. --Adipocytes (ad′i-pōs-sītz), also called adipose (ad′i-pōs; fat) cells, contain large amounts of lipid. The lipid pushes the rest of the 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. Adipocytes are rare in some connective tissue types, such as cartilage, but abundant in others, such as loose connective tissue. --Mast cells play important roles in inflammation. They contain chemicals, such as heparin, histamine, and proteolytic enzymes, that are released in response to injury, such as trauma and infection. Mast cells commonly lie beneath membranes in loose connective tissue and along small blood vessels of organs. --White blood cells, or leukocytes (see chapter 19), continuously move from blood vessels into connective tissues. The rate of movement increases dramatically in response to injury or infection. In addition, accumulations of lymphocytes, a type of white blood cell, are common in some connective tissues, such as that beneath the epithelial lining of certain parts of the digestive system. --Macrophages are large, phagocytic cells found in some connective tissue types. They are derived from monocytes, a type of white blood cell. Macrophages are either fixed, meaning that they do not move through the connective tissue, or wandering, moving in ameboid fashion through the connective tissue. Macrophages phagocytize foreign and injured cells, and they play a major role in protecting against infections. -- Platelets are fragments of hemopoetic cells containing enzymes and special proteins that function in the clotting process to reduce bleeding from a wound. --Undifferentiated mesenchymal cells are a type of adult stem cell that persist in connective tissue. They have the potential to form multiple cell types, such as fibroblasts or smooth muscle cells, in response to injury.
What is granulation tissue? How does granulation tissue contribute to scars and wound contracture
Granulation tissue, a delicate, granular-appearing connective tissue that consists of fibroblasts, collagen, and capillaries, replaces the clot. A large amount of granulation tissue is converted to a scar, which consists of dense irregular collagenous connective tissue. At first, a scar is bright red because numerous blood vessels are present. Later, the scar becomes white as collagen accumulates and the vascular channels are compressed.
What is formed from neural crest cells?
Groups of cells that break away from the neuroectoderm during development, called neural crest cells, give rise to parts of the peripheral nerves , skin pigment , the medulla of the adrenal gland, and many tissues of the face
What is ground substance?
The ground substance consists of nonfibrous molecules. It is the "shapeless" background against which the collagen fibers are seen through the microscope. The two major components are hyaluronic acid and proteoglycans.
What is the function of the inflammatory response?
The inflammatory response mobilizes the body's defenses, isolates and destroys microorganisms and other injurious agents, and removes foreign materials and damaged cells, so that tissue repair can proceed
What is the purpose of mucous connective tissue?
The mucous connective tissue helps support the umbilical cord blood vessels between the mother and the child. After birth, the mucous connective tissue can also be a rich source of stem cells.
What are the three types of cartilage? How do they differ in structure and function? Where would each type be found in the body?
HYALINE Cartilage: has large amounts of both collagen fibers and proteoglycans, Hyaline cartilage is found where strong support and some flexibility are needed, such as in the rib cage and within the trachea and bronchi. hyaline cartilage in joints has a very smooth surface. Hyaline cartilage forms most of the skeleton before it is replaced by bone in the embryo, and it is involved in growth that increases the length of bone FIBROcartilage: has more collagen fibers than proteoglycans (table 4.10b). Compared with hyaline cartilage, fibrocartilage has much thicker bundles of collagen fibers dispersed through its matrix. Fibrocartilage is slightly compressible and very tough. It is found in areas of the body where a great deal of pressure is applied to joints, such as in the knee, in the jaw, and between the vertebrae. Some joints, such as the knee, have both hyaline and fibrocartilage connective tissue. In these joints, pads of fibrocartilage help absorb shocks and prevent bone-to-bone abrasion. ELASTIC Cartilage: has numerous elastic fibers in addition to collagen and proteoglycans dispersed throughout its matrix (table 4.10c). It is found in areas that have rigid but elastic properties, such as the external ears.
Describe the function of hemopoietic tissue.
Hemopoietic (hē′mō-poy-et′ik) tissue forms blood cells. In adults, hemopoietic tissue is found in bone marrow, which is the soft connective tissue in the cavities of bones.
Define histology. Explain how the histology of tissues taken by biopsy or autopsy can be used to diagnose some
Histology is the microscopic study of tissues. Much information about a person's health can be gained by examining tissues. -A biopsy is the process of removing tissue samples from patients surgically or with a needle for diagnostic purposes. Examining tissue samples can distinguish various disorders. For example, some red blood cells have an abnormal shape in people suffering from sickle-cell disease, and red blood cells are smaller than normal in people with iron-deficiency anemia. Cancer is identified and classified based on characteristic changes in tissues. For example, changes in the structure of epithelial cells can indicate cancer of the uterine cervix, and changes in white blood cells identify people who have leukemia. Also, a greatly increased number of white blood cells can be a sign of infection. Epithelial cells from respiratory airways have an abnormal structure in people with chronic bronchitis, as well as in people with lung cancer.
What are the cellular products of endocrine glands?
Hormones: they are secreted into the bloodstream and carried throughout the body.
Describe the structure and functions of hyaluronic acid and proteoglycan aggregates.
Hyaluronic (hī′ă-loo-ron′ik; glassy appearance) acid is a long, unbranched polysaccharide chain composed of repeating disaccharide units. It gives a very slippery quality to the fluids that contain it; for that reason, it is a good lubricant for joint cavities. Hyaluronic acid is also present in large quantities in connective tissue and is the major component of the vitreous humor of the eye
Describe simple, stratified, and pseudostratified epithelial tissues.
In most cases, an epithelium is given two names, such as simple squamous, stratified squamous, simple columnar, or pseudostratified columnar. The first name indicates the number of layers, and the second indicates the shape of the cells at the free surface 1.Simple epithelium consists of a single layer of cells, with each cell extending from the basement membrane to the free surface. 2.Stratified epithelium consists of more than one layer of cells, but only the basal layer attaches the deepest layer to the basement membrane. 3.Pseudostratified columnar epithelium is a special type of simple epithelium. The prefix pseudo- means false, so this type of epithelium appears to be stratified but is not. It consists of one layer of cells, with all the cells attached to the basement membrane. There appear to be two or more layers of cells because some of the cells are tall and extend to the free surface, whereas others are shorter and do not extend to the free surface.
Describe the process of wound repair. ?
In primary union, the wound fills with blood and a clot forms (see chapter 19). The clot contains the threadlike protein fibrin (fī′brin), which binds the edges of the wound together. The surface of the clot dries to form a scab, which seals the wound and helps prevent infection. An inflammatory response induces vasodilation and takes more blood cells and other substances to the area. Blood vessel permeability increases, resulting in edema (swelling). Fibrin and blood cells move into the wounded tissues because of the increased vascular permeability. Fibrin isolates and walls off microorganisms and other foreign matter. Phagocytic white blood cells called neutrophils (noo′trō-filz) then move into the tissue to help fight the infection .. They ingest bacteria and tissue debris to clear the area for repair. Neutrophils are killed in this process and can accumulate as a mixture of dead cells and fluid called pus (pŭs).
How does healing of injuries change in older people?
Injuries in the very young heal more rapidly and more completely than in older people.
Functionally, what is unique about muscle tissue?
It is the meat of animals and constitutes about 40% of a person's body weight. As the name implies, skeletal muscle attaches to the skeleton and enables the body to move. Skeletal muscle is under voluntary (conscious) control because a person can purposefully cause skeletal muscle contraction to achieve specific body movements. However, the nervous system can cause skeletal muscles to contract without conscious involvement, as occurs during reflex movements and the maintenance of muscle tone. Skeletal muscle cells are long, cylindrical cells, each containing many nuclei located at the periphery of the cell. Some skeletal muscle cells extend the entire length of a muscle. Skeletal muscle cells are striated (strī′āt-ed), or banded, because of the arrangement of contractile proteins within the cells.
Describe three ways in which exocrine glands release secretions. Give an example of each method.
MAH: Merocrine, Apocrine, Holocrine M: The most common type of secretion is merocrine secretion. Merocrine secretion involves the release of secretory products by exocytosis. Merocrine secretion is used by water-producing sweat glands and the exocrine portion of the pancreas A: Apocrine secretion involves the release of secretory products as pinched-off fragments of the gland cells. The milk-producing mammary glands release milk by a combination of apocrine and mostly merocrine secretion. H: Holocrine secretion involves the shedding of 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. The lost cells are replaced by other cells deeper in the gland. Holocrine secretion is used by the sebaceous (oil) glands of the skin.
WHat are microvilli and what are its functions?
Microvilli are extensions of the cell that greatly increase free surface area. They occur in cells that absorb or secrete, such as serous membranes and the lining of the small intestine Microvilli are nonmotile and contain microfilaments.
How are multicellular exocrine glands classified on the basis of their duct system? Their secretory portion shape?
Multicellular exocrine glands can be classified according to the structure of their ducts and secretory regions . Simple glands have a single, nonbranched duct. If there are multiple secretory regions that branch off the duct, then the gland is called branched. Compound glands have multiple, branched ducts. For both simple and compound glands, the shape of the secretory regions further defines the gland. Glands with secretory regions shaped as tubules (small tubes) are called tubular, whereas those page 115 shaped in saclike structures are called acinar (as′i-nar) or alveolar (al-vē′ō-lar). Tubular glands can be straight or coiled. Glands with a combination of the two are called tubuloacinar or tubuloalveolar.
What is the characteristic function of nervous tissue?
Nervous tissue is found in the brain, spinal cord, and nerves and is characterized by the ability to conduct electrical signals called action potentials. Nervous tissue consists of neurons, which are responsible for its conductive ability, and support cells called glia. --Neurons, or nerve cells, are the conducting cells of nervous tissue. Just as an electrical wiring system transports electricity throughout a house, neurons transport electrical signals throughout the body.
Differentiate among multipolar, bipolar, and pseudo-unipolar neurons.
Neurons can be grouped based on their structure. --Multipolar neurons have multiple dendrites and a single axon --Bipolar neurons have a single dendrite and an axon. --Pseudo-unipolar neurons have only a single, short process that extends from the cell body and then divides into two branches, which extend to the periphery and to the central nervous syste
Differentiate between spongy and compact bone.
Spongy bone has spaces between trabeculae (tră-bek′ū-lē; beams), or plates, of bone and therefore resembles a sponge. Compact bone is more solid, with almost no space between many thin layers, or lamellae (lă-mel′ē; sing. lă-mel′ă) of bone
What are stereocilia and what are its functions?
Stereocilia are a specialized, elongated form of microvilli found in sensory structures, such as the inner ear, where they play a role in sound detection. Stereocilia are also found in some places where absorption is important, such as in the epithelium of the epididymis.
List and describe the major functions of epithelial tissue.
PBPSA 1.PROTECTING underlying structures. For example, the outer layer of the skin and the epithelium of the oral cavity protect the underlying structures from abrasion. 2.Acting as a BARRIER . Epithelium prevents many substances from moving through it. For example, the skin acts as a barrier to water and reduces water loss from the body. The skin also prevents many toxic molecules and microorganisms from entering the body. 3.Permitting the PASSAGE of substances. Though epithelium acts as a barrier for some substances, it also permits many other substances to move through it. For example, oxygen and carbon dioxide are exchanged between the air and blood by diffusion through the epithelium in the lungs. Epithelium acts as a filter in the kidney, allowing many substances to pass from the blood into the urine but retaining other substances, such as blood cells and proteins, in the blood. 4. SECRETING substances. Mucous glands, sweat glands, and the enzyme-secreting portions of the pancreas are all composed of epithelial cells that secrete their products onto surfaces or into ducts that carry them to other areas of the body. 5.ABSORBING substances. The plasma membranes of certain epithelial tissues contain carrier proteins, which regulate the absorption of materials.
Explain the difference between red marrow and yellow marrow.
Red marrow is hemopoietic tissue surrounded by a framework of reticular fibers. Hemopoietic tissue produces red and white blood cells and platelets; ----In children, the marrow of most bones is red marrow. ---Yellow marrow consists of yellow adipose tissue and does not produce blood cells. As children grow, yellow marrow replaces much of the red marrow in bones.
What is the function of reticular tissue? Where is it found?
Reticular tissue forms the framework of lymphatic tissue, such as in the spleen and lymph nodes, as well as in bone marrow and the liver. It is characterized by a network of reticular fibers and reticular cells. Reticular cells produce the reticular fibers and remain closely attached to them. The spaces between the reticular fibers can contain a wide variety of other cells, such as macrophages, blood cells, and dendritic cells, which look very much like reticular cells but are cells of the immune system
What functions would a single layer of epithelial cells be expected to perform?
Simple epithelium, with its single layer of cells, covers surfaces. In the lungs it facilitates the diffusion of gases; in the kidneys it filters blood; in glands it secretes cellular products; and in the intestines it absorbs nutrients.
Describe smooth muscle and where it can be found.
Smooth muscle forms the walls of hollow organs (except the heart); it is also found in the skin and eyes . Smooth muscle is responsible for a number of functions, such as moving food through the digestive tract and emptying the urinary bladder. Like cardiac muscle, smooth muscle is controlled involuntarily. Smooth muscle cells are tapered at each end, have a single nucleus, and are not striated.
How do nonkeratinized stratified squamous epithelium and keratinized stratified squamous epithelium differ? Where is each type found?
Stratified squamous epithelium can be classified further as either nonkeratinized or keratinized, according to the condition of the outermost layer of cells. Nonkeratinized (moist) stratified squamous epithelium, found in areas such as the mouth, esophagus, rectum, and vagina, consists of living cells in the deepest and outermost layers. A layer of fluid covers the outermost layers of cells, which makes them moist. In contrast, 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 dry, durable, moisture-resistant character. In addition to the skin, keratinized stratified squamous epithelium is also found in the gums and hard palate of the mouth.
Describe synovial membranes and their functions
Synovial (si-nō′vē-ăl) membranes line freely movable joints (figure 4.6c). Synovial membranes are made up of only connective tissue. They consist of modified connective tissue cells, page 132 either intermixed with part of the dense connective tissue of the joint capsule or separated from the capsule by areolar or adipose tissue. They produce synovial fluid, which is rich in hyaluronic acid, making the joint fluid very slippery, thus facilitating smooth movement within the joint
Structurally and functionally, what is the difference between dense regular connective tissue and dense irregular connective tissue?
The collagen fibers of dense connective tissue resist stretching and give the tissue considerable strength in the direction of the fiber orientation. Tendons and most ligaments consist almost entirely of thick bundles of densely packed, parallel collagen fibers with the orientation of the collagen fibers in one direction, which makes the tendons and ligaments very strong, cablelike structures. -- Dense irregular connective tissue forms sheets of connective tissue that have strength in many directions but less strength in any single direction than does regular connective tissue.
What adult structures are derived from each layer?
The endoderm , the inner layer, forms the lining of the digestive tract and its derivatives. The mesoderm , the middle layer, forms tissues such as muscle, bone, and blood vessels. The ectoderm , the outer layer, forms the skin; a portion of the ectoderm called neuroectoderm becomes the nervous system. .
Name the four primary tissue types and the characteristics that are used to classify them. diseases.
The four primary tissue types, from which all organs of the body are formed, are epithelial tissue, connective tissue, muscle tissue, and nervous tissue. -Body tissues are classified into four types, based on the structure of the cells, the composition of the noncellular substances surrounding the cells (called the extracellular matrix), and the functions of the cells.
What is the function of each of the following characteristics of an epithelial free surface: is smooth, has cilia, has microvilli, is folded? Give an example of where each surface type is found in the body.
The free surfaces of epithelial tissues can be smooth or folded; they may have microvilli or cilia. Smooth surfaces reduce friction. For example, the lining of blood vessels is a simple squamous epithelium that reduces friction as blood flows through the vessels - - -
What are the three formed elements in blood?
There are three types of cellular structures: red blood cells, white blood cells, and cell fragments called platelets. White blood cells sometimes leave the bloodstream and wander through other tissues.
Describe the changes in cell shape and number of cell layers in transitional epithelium as it is stretched. Where is transitional epithelium found?
These are structures where considerable expansion can occur. The shape of the cells and the number of cell layers vary, depending on the degree to which transitional epithelium is stretched. The surface cells and the underlying cells are roughly cuboidal or columnar when the epithelium is not stretched, and they become more flattened or squamouslike as the epithelium is stretched. Also, as the epithelium is stretched, the epithelial cells can shift on one another, so that the number of layers decreases from five or six to two or three. lines the urinary bladder, ureters, pelvis of the kidney (including the major and minor calyces;), and superior part of the urethra
Define tissue repair. Differentiate between repair by regeneration and repair by replacement.
Tissue repair is the substitution of viable cells for dead cells by regeneration or replacement. In regeneration , the new cells are the same type as those that were destroyed, and normal function is usually restored. In replacement, a new type of tissue develops, which eventually produces a scar and causes the loss of some tissue function. Most wounds heal through regeneration and replacement; which process dominates depends on the tissues involved and the nature and extent of the wound.
What components are found in a tissue?
Tissues are collections of specialized cells and the extracellular substances surrounding them.
What structural features distinguish adipose tissue from other types of connective tissue?
dipose tissue consists of adipocytes, which contain large amounts of lipid. Unlike other connective tissue types, adipose tissue is composed of large cells and a small amount of extracellular matrix, which consists of loosely arranged collagen and reticular fibers with some scattered elastic fibers. Blood vessels form a network in the extracellular matrix. Adipose tissue functions as an insulator, a protective tissue, and a site of energy storage. Lipids take up less space per calorie than either carbohydrates or proteins and therefore are well adapted for energy storage.
Contrast healing by primary union and healing by secondary healing. Which process is better, and why?
epair by secondary union proceeds in a similar fashion, but with some differences. Because the wound edges are far apart, the clot may not close the gap completely, and it takes the epithelial cells much longer to regenerate and cover the wound. Also, the increased tissue damage means that both the degree of inflammation and the risk of infection are greater and there is more cell debris for the phagocytes to remove. Much more granulation tissue forms, and the contraction of fibroblasts in the granulation tissue leads to wound contracture, resulting in disfiguring and debilitating scars. Thus, it is advisable to suture a large wound, so that it can heal by primary rather than secondary union. Healing is faster, with a lowered risk of infection and a reduced degree of scarring.
List the major functions of connective tissue, and give an example of a type of connective tissue that performs each function.
escsscitp 1. Enclosing and separating other tissues:Sheets of connective tissue form capsules around organs, such as the liver and kidneys. connective tissues separate muscles, arteries, veins, and nerves from one another. 2.Connecting tissues to one another: Tendons attach muscle to bone, and ligaments hold bones and bones together. 3.Supporting and moving parts of the body:CARTILAGE AND JOINTS. semirigid cartilage supports structures such as the nose, ears, and joint surfaces. Joints between bones allow one part of the body to move relative to other parts. 4.Storing compounds: Adipose tissue (fat) stores high-energy molecules, and bones store minerals, such as calcium and phosphate 5.Cushioning and insulating: Adipose tissue cushions and protects the tissue it surrounds and provides an insulating layer beneath the skin that helps conserve heat. 6.Transporting: Blood transports the gases, nutrients, enzymes, hormones, and cells of the immune system throughout the body. 7.Protecting: Cells of the immune system and blood protect against toxins and tissue injury, as well as against microorganisms. Bones protect underlying structures from injury.
Name the five manifestations of inflammation; explain how each is produced and the benefits of each.
redness, heat, swelling, pain, and disturbed function. 1. REDNESS HEAT AND SWELLING: After a person is injured, chemical substances called chemical mediators are released or activated in the tissues and the adjacent blood vessels. The mediators are histamine, kinins, prostaglandins, leukotrienes, and others. Some mediators induce dilation of blood vessels and produce redness and heat. Dilation of blood vessels is beneficial because it speeds the arrival of white blood cells and other substances important for fighting infections and repairing the injury. 2. SWELLING AND PAIN: Chemical mediators also stimulate pain receptors and increase the permeability of blood vessels. The increased permeability allows materials such as clotting proteins and white blood cells to move out of the blood vessels and into the tissue, where they can deal directly with the injury. As proteins from the blood move into the tissue, they change the osmotic relationship between the blood and the tissue. Water follows the proteins by osmosis, and the tissue swells, producing edema (e-dē′mă). Edema increases the pressure in the tissue, which can also stimulate neurons and cause pain. 3. CLOTTING AND DISTURBED FUNCTION: Clotting isolates the injurious agent and separates it from the rest of the body. Foreign particles and microorganisms at the site of injury are "walled off" from tissues by the clotting process. Pain, limitation of movement resulting from edema, and tissue destruction all contribute to the disturbed function