Practical 1 Flashcards
what determines the epithelium
organization and shape of the cells determines the type
three basic types of epithelial cells
squamous, cuboidal, and columnar
major difference between simple and modified epithelium
A simple epithelium is composed of a single cell type, while a modified epithelium has at least one additional cell type interspersed among the epithelial cells
when is epithelium referred to as simple
when only one cell layer thick
when is epithelium referred to as stratified
when it is 2 or more cell layers thick
what is the classification of epithelial cells determined by
the way the cells appear in sections taken at right angles to the surface of the epithelium. If the epithelium is stratified, it is classified according to the outermost layer of cells, the cells facing the lumen
Pyramidal cells
wider at the base than at the apex, and are found in glands
Transitional cells
rounded or domes shaped at the luminal surface, and are found exclusively in the urinary system.
name the apical speciliazations on the surface of some epithelial cells
microvilli, cilia, and stereocilia
microvilli
also known as brush borders or striated borders, and serve to increase surface area
Cilia
used to move extracellular material (mucus, particles, etc.) over the surface of the epithelium
Stereocilia
elongated microvilli found in the sensory cells of the ear
goblet cell
are glandular simple columnar epithelial cells whose sole function is to secrete mucin, which dissolves in water to form mucus. They use both apocrine and merocrine methods for secretion.
where are goblet cells located
epithelial lining of organs, such as the intestinal and respiratory tracts. They are found inside the trachea, bronchus, and larger bronchioles in respiratory tract, small intestines, the colon, and conjunctiva in the upper eyelid
brush border
name for the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells found in certain locations of the body...when found in kidney referred to as brush border
what are the 2 main locations where brush border cells are found
The small intestine tract, The kidney: Here the brush border is useful in distinguishing the proximal tubule (which possesses the brush border) from the distal tubule (which does not)
striated border
same as brush border, however, striated border refers specifically to microvilli of intestinal cells
Haversian canal
a series of tubes around narrow channels formed by lamellae. This is the region of bone called compact bone. Osteons are arranged in parallel to the long axis of the bone. The Haversian canals surround blood vessels and nerve cells throughout the bone and communicate with osteocytes in lacunae (spaces within the dense bone matrix that contain the living bone cells) through canaliculi. This unique arrangement is conducive to mineral salt deposits and storage which gives bone tissue its strength
lacunae (bone)
SPACES WITHIN THE BONE MATRIX The Lacunae are situated between the lamellae, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte.
lacunae (cartilage)
The cartilage cells or chondrocytes are contained in cavities in the matrix, called cartilage lacunae; around these the matrix is arranged in concentric lines, as if it had been formed in successive portions around the cartilage cells. This constitutes the so-called capsule of the space. Each lacuna is generally occupied by a single cell, but during the division of the cells it may contain two, four, or eight cells. Lacunae are found between narrow sheets of calcified matrix that are known as lamellae
lamellae
A lamella is a thin plate-like structure, often one amongst many lamellae very close to one another, with open space between. Aside from respiratory organs, they appear in other biological roles including filter feeding, the traction surfaces of geckos,[1] and chloroplast membranes where high permeability is important.
osteocyte
a bone cell, extends numerous processes into small tunnels called canaliculi, surrounded by secreted matrix
canaliculi
connecting adjacent lacunae and allow contact btwn cell processes of neighboring osteocytes, located in mineralized matrix.
osteoblasts
cells that secrete extracellular matrix of bone, once cell surrounded with secreted matrix referred to as an osteocyte
chondrocytes
specialized cells that produce and maintain extracellular matrix in cartilage, in hyaline cartilage, they are distributed either singularly or in clusters called isogenous groups
isogenous groups
clusters of chonrocytes formed from recently divided cells, disperse as they produce matrix material. also secrete metalloproteinases, enzymes that degrade cartilage matrix, allowing cells to expand and reposition themselves withing the growing isogenous group
how does chondrocyte appearance vary according to their activity?
active chondrocytes display areas of cytoplasmic basophilia = indicative of protein synthesis and clear areas. in older, less active cells, golgi apparatus is smaller, clear areas of cytoplasm, considerable distortion from shrinking as glycogen and lipids are lost
elastic cartilage
Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear, larynx, and epiglottis. It contains elastic fiber networks and collagen fibers.[1] The principal protein is elastin.Elastic cartilage is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix. These fibers form bundles that appear dark under a microscope. These fibers give elastic cartilage great flexibility so that it is able to withstand repeated bending. The chondrocytes lie between the fibres. It is found in the epiglottis (part of the larynx) and the pinnae (the external ear flaps of many mammals including humans). Elastin fibers stain dark purple/black with Verhoeff stain.
Elastic cartilage
Elastic cartilage is very similar to hyaline cartilage, is involved in provideing flexible support, and is characterized by a high content of elastic fibers. When selectively stained for elastic fibers, a network of dark brown or black fibers is evident
Intramembranous Ossification
formed without the intervention of a cartilage precursor, bone is formed by differentiation of mesenchymal cells into osteoblasts
endochondral ossification
begins with prolifieration and aggregation of mesenchymal cells at site of future bone, influence of different fibroblastic growth factors and proteins cause mesenchymal cells to initially express type II collagen and differentiate into chondroblasts, producing cartilage matrix. 1) initially, a hyaline cartilage model w/ general shape of bone formed2) first sign of ossification is appearance of a cuff of bone around cartilage model -- perichondrial cells no longer give rise to chondrocytes. instead osteoblasts are produced. altered role of no longer functioning as a perichondrium gives rise to new name, periosteum. an osteogenic layer can be ID'd w/in periosteum. 3) w/ establishment of periosteal bony collar, chondrocytes in midregion of cartilage model become hypertrophic. -- chondrocytes enlarge, surroudning cartilage matrix is resorbed and forms thin irregular cartilage plates btwn hpyertrophic cells. hypertrophic cells synthesize alkaline phosphatease, surrounding cartilage matrix undergoes calcification
elastic connective tissue
Elastic fibers - elastic microfibrill & elastin extracellular matrix
Reticular Connective Tissue
type of connective tissue.[1] It has a network of reticular fibers, made of type III collagen.[2] Reticular fibers are not unique to reticular connective tissue, but only in this type are they dominantReticular connective tissue is found around the liver, the kidney, the spleen, and lymph nodes, as well as in bone marrow, adipose tissue held together by reticular fibers
Transitional Epithelium
type of tissue consisting of multiple layers of epithelial cells which can contract and expand. These cells, part of the epithelium, are found in the urinary bladder, in the ureters, and in the superior urethra and gland ducts of the prostate.
ID
transitional epithelium
hyaline cartilage
The extracellular matrix of hyaline cartilage is resistant to compression due to its high water content. Hyaline cartilage is bounded by a sheath of connective tissue called the perichondrium. New cartilage is formed when cells of the perichondrium undergo a transformation, and begin to produce extracellular matrix. As these chondroblasts secrete matrix, they become surrounded and eventually trapped in the lacuna and are then called chondrocytes.
Mesenchyme
Mesenchyme is the embryonic precursor of all connective tissue (other tissues are derived from mesenchyme, but here we only deal with connective tissue). The mesenchymal cells are motile, or moving, and migrate to specific areas of the embryo. The cells will appear stellate (star shaped) and may have long, branching processes. Mesenchyme is predominant in embryos, but can also be found in adult animals. Mesenchyme found in the adult maintains its ability to form other types of connective tissue cells.
Loose (Areolar) Connective Tissue:
Loose connective tissue has a higher concentration of cells, relatively few fibers, and abundant ground substance. The fibers are arranged in a loose random web. Most of the cells found in loose connective tissue are fibroblasts. Fibroblasts are described as being in one of two states. Inactive fibroblasts have elongate, densely stained nuclei, little cytoplasm, and are by far the most common cell in this tissue. Active fibroblasts, cells that are actively synthesizing proteins, have rounder nuclei, and lots of granular cytoplasm. Macrophages can be a challenge to identify unless in the process of phagocytosis. In general, macrophages have a kidney-shaped nucleus, and vacuoles and lysosomes. There may be nearly as many macrophages as inactive fibroblasts in loose connective tissue.
Dense Regular Connective Tissue
Dense regular connective tissue is exemplified by tendon. The prominent feature of dense regular connective tissue is the large number of fibers (composed of Type I collagen) which are packed in long parallel bundles, little ground substance and limited cells In tendon, fibroblasts are located between the bundles of collagen fibers, and only the nuclei are visible. Collagen fibers often appear wavy
Dense Irregular Connective Tissue
While fibers are still the major component of this type of connective tissue, the fibers are more randomly arranged than fibers in dense regular connective tissue.
Elastic Connective Tissue
A predominance of elastic fibers is the defining feature of elastic connective tissues. Composed of elastin, elastic fibers are thinner than collagen fibers and appear as a three dimensional web of fibers. Elastic fibers are not well stained by eosin and thus are sometimes more difficult to identify unless the preparation has been specifically stained to reveal them. The middle layer of large arteries (e.g. aorta) have especially high concentrations of elastic fibers.
Reticular Connective Tissue
Reticular fibers form a meshwork to give structure to organs where populations of cells are moving through rather than fixed in place. Examples are bone marrow or the lymphatic system (e.g. lymph nodes, spleen). They are also found in loose connective tissue. Reticular fibers are very hard to see unless they are stained with specific stains. When stained with silver-staining procedures, reticular fibers appear black and threadlike
Unilocular Adipose Tissue
Unilocular adipose cells have a single large lipid droplet as their name implies. This large droplet occupies most of the cell, displacing the nucleus to the periphery of the cell, and leaving a slim ring of cytoplasm. These cells are very large, and often are grouped together to form white adipose tissue. In most fixed tissue, the lipid is dissolved away, and the unilocular cell appears as an empty ring with the nucleus at one side (often described as a signet ring).
Multilocular Adipose Tissue
Multilocular adipose cells have several small droplets in the cytoplasm, an eccentric but unflattened nucleus, and numerous mitochondria lending the cell a brownish color. Some describe the numerous lipid droplets as giving multilocular adipose tissue a sudsy appearance.The cells of cartilage (chondrocytes and chondroblasts) and bone (osteoblasts and osteocytes) are found in lacunae, or cavities in the extracellular matrix orconnective tissue. In both cartilage and bone, the extracellular matrix is relatively hard, and plays an important role in supporting the organs and tissues of the body.
Osteoclasts
Bone is highly organized with osteocytes located in lacuna arranged in concentric circles around a central canal called an Haversian canal.
bone
Bone is highly organized with osteocytes located in lacuna arranged in concentric circles around a central canal called an Haversian canal. The collection of osteocytes arranged in concentric lamelli around the Haversian canal is called an osteon. The osteocytes extend processes, called canaliculi, to contact process of osteocytes in neighboring lamelli
Endochondral Ossification
In Endochondrial Ossification a cartilage template of long bones is converted into bone. The persistence of an expanding plate of cartilage at the base of the head (epiphysis) of the bone on each end allows for the elongation of the bone during growth. Elongation occurs at this expanding plate called the epiphyseal growth plate located between the epiphysis and diaphysis of the bone. Note the hyaline cartilage at one end of the epiphyseal plate. This is the Resting zone, composed of hyaline cartilage, which will eventually become bone. The next layer is the Zone of Proliferation. In this layer, the chondrocytes undergo several mitotic divisions, and form columns of cells. The matrix between the columns of chondrocytes should be strongly stained (in this case with Alcian Blue). The Zone of Hypertrophy is a thin transitional zone where the chondrocytes have stopped dividing, and increase in size. As the chondrocytes grow, the extracellular matrix is reduced. The cells become greatly enlarged, and the extracellular matrix becomes calcified. This is the Zone of Calcification. This layer should be fairly lightly stained, and there should be little extracellular matrix present. The chondrocytes degenerate, and the lacunae are invaded by osteogenic cells and capillaries. The osteogenic cells become osteoblasts, and begin producing bone. This zone is the Osteogenic Zone, and the extracellular matrix should be darkly stained.
Intramembranous Ossification
This type of ossification takes place in the flat bones, and is typified by the development of the skull. In this type of bone formation, mesenchymal cells condense and differentiate into osteoblasts. These form centers of ossification, and begin producing bone. Note that there is no cartilage precursor to the bone, nor is there any cartilage present at all. The bones continue to spread eventually forming a sheet.
Smooth muscle
Smooth muscle is primarily responsible for involuntary movements. It is found in the digestive tract, walls of arteries and veins, respiratory passageways, bladder, and the reproductive system. In many cases (digestive, circulatory and some reproductive), the contractions of smooth muscle travel in waves through an entire sheet (or bundle) of muscle cells. Smooth muscle fibers are mononucleated, long, and spindle shaped. Although individual cell boundaries are hard to see, the nucleus is centrally located in the cell. When you look at slides of intestine, notice that the smooth muscle is arranged in two layers with different orientations. The outermost layer (farthest from the lumen) runs longitudinally along the length of the intestine. The inner layer is circularly oriented and forms tight spiral around the epithelium and lumen of the intestine. Muscular arteries have a similar arrangement of smooth muscle, circular and longitudinal layers, though this arrangement is more difficult to see.
Skeletal muscle
Skeletal muscle fibers are long cylindrical cells that are formed by the fusion of myoblasts (muscle precursor cells), resulting in a large multinucleated cell. In mammals, muscle fiber nuclei are displaced to the side of the cell, and are flattened against the cell membrane by the bundles of contractile fibers (myofibrils) that occupy most of the cytoplasm. The cell membrane is called the sarcolemma and defines the boundaries of a single muscle cell. Just outside the sacrolemma of each muscle fiber is its basal lamina. Within the basal lamina are found satellite cells, the stem progenitor cells of skeletal muscle. A cluster of muscle fibers is enclosed by a connective tissue sheath called an endomysium. Clusters of muscle fibers are gathered into groups ensheathed by the perimysium. Finally, the entire muscle is surrounded by a sheath of dense connective tissue called the epimysium. Several structures can be found in these connective tissue sheaths including nerves, arteries, veins and capillaries. Golgitendon organs and muscle spindles are specialized structures for sensing muscle length; these may be observed in your sections (see Ross Figures 11.12). Skeletal muscles are attached to bone via tendons (dense connective tissue).
Cardiac Muscle
Cardiac muscle is a specialized type of striated muscle found only in the heart. Cardiac muscle fibers have one or two centrally-located nuclei. Unlike skeletal muscle fibers, cardiac muscle fibers branch. Cardiac muscle cells are joined together by intercalated disks forming a network of interconnected cells. The intercalated disks appear as dark stained bands at the juncture between cardiac muscle fibers. The intercalated disks contain gap junctions, which allow excitatory impulses to travel from muscle cell to muscle cell, desmosomes to bind the cells together, and fascia adherens (adhering junctions) to provide an anchor for the actin thin filaments of the muscle cell. Purkinje fibers, specialized cells for conducting the action potential in the heart, may also be observed.
Purkinje fibers
specialized cells for conducting the action potential in the heart, may also be observed.
Peripheral Nerves
Peripheral nerves consist of bundles (fascicles) of axons surrounded by a connective tissue sheath (epineurium). Most nerves are mixed; they contain axons of both sensory and motor neurons. Each individual axon is surrounded by a thin layer of loose connective tissue, the endoneurium. In addition, each fascicle of axons is surrounded by a perineurium. Most of the axons in slide 100 are myelinated. In cross section, these fibers look like tiny doughnuts. The doughnut hole corresponds to the actual axon, while the doughnut, the empty space, corresponds to the myelin sheath which was removed during the staining process. In longitudinal sections of axons or whole mounts of axons (intact cells), the unmyelinated node between myelinated segments called the node of Ranvier may be detected.
Spinal Cord
The spinal cord is divided into a central "H" shaped region of gray matter, and the surrounding white matter layer (Ross et al, Fig. 12-26). The gray matter is arranged into two dorsal and two ventral horns. Each dorsal horn receives input from sensory neurons in a dorsal root ganglion. If your section is through the upper (cervical) spinal cord, two small lateral horns may also be present. Motor neurons in the ventral horn transmit impulses to skeletal muscles. These neurons have large triangular or star-shaped cell bodies and are easy to see. Locate and be able to identify: the ventral fissure, dorsal root ganglia, dorsal and ventral horns, and ventral horn motor neurons.
Cerebrum (cerebral cortex)
The brain is organized like an inside-out spinal cord. White matter inside is surrounded by a multilayered cerebral cortex of gray matter. Pyramidal cells, the most prominent neurons in the cerebral cortex, are triangle shaped with a single large apical dendrite.
Cerebellum
The cerebellum also is composed of an inner white matter and an outer gray matter. The gray matter, the cerebellar cortex, has an outer layer, the molecular layer, with relatively few cell bodies. The inner layer, the granular layer, has abundant cell bodies, evident by the presence of nuclei. Interposed between the molecular and granular layer is a single layer of extremely large flask-shaped cells called Purkinje cells.
Pacinian Corpuscles
PC- Pacinian CorpuscleSC- concentric layers of flattened Schwann CellsNF- single central Nerve Fiber