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1
Q

Acidophilic

A

Structures that stain witheosin, anegatively chargeddye that stainspink to red. Acidophilic tissue componenets have a net positive charge such as proteins (NH2+). Examples of acidophilic components: mitochondria (due to membrane proteins), Lysosomes (due to enzymes) erythrocytes (hemoglobin), collagen fibers, secretory vacuoles that contain proteins, and cytosolic proteins.

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2
Q

Acrosome

A

A modified lysosome at the tip of the head of a sperm which contains lytic enzymes (hyaluronidase in mammalian sperm) which digest the outer surface of the egg and allow the sperm to inject its haploid DNA. The release of these enzymes is called the acrosome reaction and is triggered when a spermatozoon binds to a secondary oocyte.

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3
Q

Actin

A

Afilamentous protein(42 kD) involved in muscle contraction in both smooth and striated muscle. It is the main constituent of thethin filamentsof muscle fibers. Actin also makes up the microfilaments that form part of the cytoskeleton. Actin filaments (known also as filamentous or f-actin) can be dissociated into their globular subunits. This is known as globular or g-actin.

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4
Q

Adventitia

A

Theoutermost connective tissuelayer of any hollow organnot covered by a serosa. An adventitia plus a mesothelium makes a serosa.

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5
Q

Afferent

A

Moving orcarrying inwardor toward a central part, such as anafferent arteriole, which carries unfiltered blood toward the glomerulus.(see efferent for more examples)

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6
Q

Aldehyde fuchsin

A

A stain that produces violet staining ofelastic fibers, mast cell granules, gastric chief cells, beta cells of the pancreatic islets.

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7
Q

Ampulla

A

A dilated portion of a tubular structure, e.g. the ampulla of Vater (major duodenal papilla) or the ampulla of the oviduct.

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8
Q

Anaphase

A

The stage of mitosis or meiosis beginning with theseparation of sister chromatids(or homologous chromosomes) followed by their movement towards the poles of the spindle.

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9
Q

Anisocytosis

A

A condition where thered blood cells are unequal in size, evident on blood smear. This condition could be due to low vitamin B12, folic acid and iron. Anisocytosis often involves a mixture of macrocytes (abnormally large cells) and microcytes (abnormally small cells) in the same sample.

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10
Q

Annulus

A

Aring like structure, e.g. the annulus fibrosus of D23an intervertebral disc.

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11
Q

Anterograde

A

Movingor extendingforward(antonym: retrograde). Anterograde transport in a neuron involves transport away from the neuronal cell body and toward the peripheral processes

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12
Q

Antrum

A

A general term forcavity or chamber within a certain organsor sites in the body. The antrum of the stomach (gastric antrum) is a portion before the outlet which is lined by mucosa which does not produce acid. Also the antrum in secondary & tertiary ovarian follicles.

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13
Q

Apical

A

Relating to or located at thetip(an apex). The apical membrane of a cell is the part that lines the luminal surface (antonym: baso-lateral membrane).

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14
Q

Apocrine

A

Form of secretion in which someportion of the cell is shed along with the secretory product.example: the secretion of lipid droplets by cells of the lactating mammary gland. The fat drople lacks a membrane when it is in the cytoplasm, but leaves the cell by budding from the apical plasma membrane, taking with it a piece of the membrane.

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15
Q

Apoptosis

A

Programmed cell deathas signaled by the nuclei or external factors in normally functioning human and animal cells when age or state of cell health and condition dictates. This active process requires metabolic activity by the dying cell, which is characterized by cleavage of the DNA into fragments that give a so called laddering pattern on gels. Cells that die by apoptosis show margination of chromatin, nuclear blebbing fragmentation into membran-bounded apototic bodies that arephagocytosedby macrophages or neighboring cells. These do not usually elicit an inflammatory response. Apoptosis is distinct from necrosis where dying cells break open, and the intracellular components trigger an inflammatory reaction.

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16
Q

Arcuate

A

Curved like a bow. Examples include the median/medial/lateral arcuate ligaments of the diaphragm, the arcuate line of the transversalis fascia and arcuate vessels of kidney.

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17
Q

Atrophy

A

Awasting away, a diminution in the size of a cell, tissue, organ or part.

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18
Q

Autocrine

A

Secretionof a substance, such as a growth factor, thatstimulates the secretory cell itself. One example is interleukin-2 release by T cells, which induces the proliferation of the same T cell as well as other T cells.

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19
Q

Autophagy

A

Removal of cytoplasmic components, including membrane bounded organelles, by digesting them within secondary lysosomes (autophagic vacuoles). Mechanism: A region of cytoplasm becomes surrounded by primary lysosomes which fuse with one another to form a double membrane around the cytoplasmic region. The lysosomal enzymes are initially limited to the space between the two membranes. The inner membrane breaks down, giving the enzymes free access to the enclosed region of cytoplasm.

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20
Q

Axon

A

Along process of a neuron, that carries efferent (outgoing) action potentials from the cell body towards target cells. Axons can be identified by the presence of an axon hillock (tapering region between a neuron’s cell body and its axon that is pale-staining because it lacks Nissl bodies).

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21
Q

Axoneme

A

The9+2 arrangement of microtubule(9 doublets + a pair of complete microtubules) that forms the core of a cilium or flagellum

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22
Q

Basal

A

In morphologicallypolarized epithelial cells, the surface closest to thebasement membrane.

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23
Q

Basal body

A

The structure from which a cilium develops. Has9 triplets of microtubules, similar to the arrangement in a centriole.

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24
Q

Basal lamina

A

Terminology varies from book to book. We consider a basal lamina to be an electron dense layer visible by EM that lies between an epithelium and connective tissue layer and helps bind the two together. The basal lamina and the reticular lamina form the basement membrane. The basal lamina (or lamina densa) is produced by epithelial cells and contains type IV collagen. The reticular lamina is formed by the connective tissue cells and contains reticular fiber of type III collagen. Between the epithelial cells and the basal lamina lies a pale-staining layer (the lamina lucida or lamina rara).

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25
Q

Basophilic

A

Tissue components that carry a net negative charge and therefore bind positively charged dyes such as hematoxylin.Basophilic tissue components includeDNA, RNA (PO4) Proteoglycans, and GAGs (SO4, CO2). Examples of basophilic structures include: nucleus, nucleolus, and ribosomes.

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26
Q

Best’s carmine

A

A stain used for thedemonstration of glycogen in tissues.

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27
Q

Bouin’s

A

A common fixative for light microscopy. It includes formalin, acetic acid and picric acid.

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28
Q

Brush border

A

Thedensely packed microvillion the apical surface of, for example, the cells of the proximal tubules of the nephron.

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29
Q

Canaliculus

A

Literally a little channel or canal. In bone: canaliculi radiate from lacuna. House cytoplasmic processes of osteocytes.

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32
Q

Centriole

A

Small cylindrical structures composed of nine microtubule triplets; they constitute the core of themicrotubule organizing center (MTOC) in thecentrosome

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33
Q

Centrosome

A

A zone of cytoplasm usually located near the nucleus that contains the Golgi apparatus and a pair of centrioles (Wheater, Figs. 1.9b & 1.25). Also called the cytocentrum. Sometimes distinguishable by LM (Wheater, Fig. 1.9c) because the organelles it contains stain poorly with H&E.

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34
Q

Chromophil

A

Characterized by secretory granules having high affinity for histological dyes. In the pituitary there are 2 types of chromophils: acidophils & basophils.

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38
Q

Chromophobe

A

Cells whose cytoplasm does not take up stain readily. Located in pars distalis. Possibly degranulated chromophils. Include folliculostellate cells which make up a large portion of cells in pars distalis.

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39
Q

Cilium

A

Motile hair-like projections that emanate from the surface of certain epithelial cells. Specialized function in propelling mucus and other substances over the surface of epithelium via rapid wave’like oscillations.

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42
Q

Clathrin

A

A protein involved in intracellular vesicular transport. Clathrin triskelions (protein complexes with a three-armed structure) coat the cytoplasmic aspect of certain cytoplasmic membranes such as the trans golgi network, causing the coated parts of the membrane to bud off as a vesicle. Example: formation of lysosomes in the trans golgi network where mannose-6-phosphate is bound. The clathrin-coated pit deepens to form a vesicle (lysosome) which then loses its clathrin coat and can then fuse (and release its contents) to a late endosome.

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44
Q

Connexon

A

A gap junction is made up of many connexons. A connexon is a cylindrical structure that consists ofsix copies of the transmembrane proteinconnexin.Connexons are aqueous pores through the plasma membrane. Paired connexons in neighboring cell membranes form hydrophilic channels that permit the passage of ions, amino acids, cAMP, etc., directly from the cytosol of one cell to the cytosol of the other. Connexons are regulated by pH and Ca2+ (high pH/low Ca2+ opens connexons).

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45
Q

Constitutive

A

Continuousand without regulation, as in constitutive vs. regulated secretion.

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46
Q

Cortex

A

A histologically distinct region located at theperiphery of an organ. Examples include renal cortex, suprarenal cortex, thymic cortex.

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47
Q

Crista

A

Folds of the inner mitochondrial membrane. Cristae greatly increase the surface area where theelectron transport chain and ATP synthase are located. Numerous cristae therefore indicate a high energy requirement in that cell.

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49
Q

Cumulus

A

Cumulus literally means “hill.” Thus “cumulus oophorus” is the hill that carries the egg.

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50
Q

Cytokinesis

A

Stage in cell division where division of cytoplasm occurs. Cleavage furrow begins inlate anaphasebut cytokinesis is best characterized intelophase.

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53
Q

Cytosol

A

Water and theinorganicandorganic chemicalssuspended in it that make up thebulk of the cytoplasm. All cytoplasmic organelles are surrounded by the cytosol. Cytoplasm = cytosol + cytoplasmic organelles + cytoplasmic inclusions (e.g., lipid droplets, glycogen).

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54
Q

Demilune

A

Demilune means “half moon,” i.e. shaped like a crescent moon. A serous demilune is a half-moon shaped group of serous cells associated with the outer surface of amucous acini(e.g., in submandibular and sublingual glands).

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55
Q

Dendrite

A

Processes specialized forreceiving stimuli from sensory cells, axons, and other neurons.Often multibranched.

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56
Q

Desmosome

A

One of the three components of junctional complex between epithelial cells (other two are the zonula occludens and zonula adherens). Also occur in epithelia & muscle as individual desmosomes that are not part of a junctional complex.

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57
Q

Diapedesis

A

Process by whichleukocytes leave the bloodstreamby migrating between the endothelial cellsof the blood vessels to enter the connective tissue spaces where they perform their major functions.

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58
Q

Diaphysis

A

Shaft of a long bone

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59
Q

Dyad

A

Present near Z-line of cardiac muscles, composed of aT-tubule and a terminal cisternae of the sarcoplasmic reticulum. Important in excitation-contraction coupling.

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60
Q

Dynein

A

Microtubule-associated protein responsible formoving vesiclesalong the microtubules in retrograde transport. Ciliary dynein forms arms associated with each microtubules doublet in the axoneme. The ATPase activity of the dynein slides one doublet relative to the next during ciliary movement.

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61
Q

Dysplasia

A

A disordered pattern of growth, most often encountered in epithelia. May involve loss of cell orientation, variation in cell size and shape, and increased numbers of mitotic cells that are often found in unusual locations within the epithelium.

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62
Q

Efferent

A

Leading away from. Examples: 1) Functionally, the PNS is divided into asensory (afferent) component, which receives and transmits impulses to the CNS for processing, and amotor (efferent) component, which originates in the CNS and transmits impulses to effector organs throughout the body. 2)Afferent lymphaticvesselsdeliver lymph into the lymph nodes, while efferent lymphatics carry lymph away from the node after it has passed through it.

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63
Q

Endocrine

A

A gland that lacks a duct and secretes into surrounding connective tissue, where the hormone is picked up by the bloodstream. Does not secrete into a lumen or onto the body surface. E.g., Adrenal (suprarenal) glands, thyroid, enteroendocrine (DNES or diffuse neuroendocrine system) cells.

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64
Q

Endocytosis

A

Process whereby acell ingestsmacromolecules, particulate matter, and other substances from the extracellular space.

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65
Q

Endomitosis

A

Process whereby the DNA replicates without subsequent division of the nucleus or the cell; instead, ithe cellbecomes larger and the nucleus becomes polyploid, as much as 64 N, sometimes more. Megakaryoblasts undergo endomitosis prior to platelet formation.

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66
Q

Endomysium

A

Composed ofreticular fibersand anexternal lamina(basal lamina), surrounds each muscle cell.

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67
Q

Endoneurium

A

Theinnermost layerof the three connective tissue investments of a nerve. It surrounds individual nerve fibers and consists mainly of collagen fibrils.

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68
Q

Epineurium

A

Outermost layerof the three connective tissue investments covering a nerve. It surround the entire nerve, usually binding multiple fascicles together. It consists of dense irregular connective tissue, sometimes associated with adipose tissue.

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69
Q

Epiphysis

A

Articular end of long bone.

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70
Q

Euchromatin

A

Active form of chromatinwhere genetic material of the DNA molecule is uncoiled and is either being replicated or being transcribed into RNA. Euchromatic areas of a nucleus are pale-staining by LM or EM.

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71
Q

Exocrine

A

Secreting into a lumen (e.g. the stomach) or onto the body surface, usually via aduct.

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72
Q

Exocytosis

A

Release of materialfrom the cell byfusion of a membrane-bounded vesiclewith the plasma membrane

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73
Q

Fibrillin

A

Widely distributedconnective tissue proteinthat forms the microfibril on which elastin is laid down to form elastic fibers. Absence of these microfibrils results in formation of elastic sheets (lamellae) rather than elastic fibers.

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75
Q

Formalin

A

A 37% aqueous solution of formaldehyde. Themost common fixative agentused in light microscopy.

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76
Q

Fundus

A

Therounded end of a hollow organ farthest from the outflow opening.e.g. fundus of stomach, gall bladder, and uterus.

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77
Q

GAG (Glycosaminoglycan)

A

Negatively charged, long, unbranched, rod-like chains ofrepeating disaccharidesthat have the capability of binding large quantities of water. GAGs associate with a core protein to form proteoglycans.

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78
Q

Ganglion

A

A general term fora group of nerve cell bodies located outside the central nervous system, occasionally applied to certain nuclear groups within the brain or spinal cord, for example basal ganglia.

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79
Q

Glutaraldehyde

A

Adialdehyde used as a fixative, especially for electron microscopy. By its interaction with amino groups (and others) it forms cross links between proteins.

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80
Q

Glycocalyx

A

Also called the cell coat. The fuzzy layer, seen by electron microscopy, on the outer surface of the plasmalemma. Especially prominent on enterocytes of the intestine & proximal tubules of the kidney. It is rich in proteoglycans, glycolipids, and glycoproteins. A thick glycocalyx may be visible by LM after special staining (e.g. PAS)

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81
Q

Haustra

A

Large intestine sacculationsmaintained by taeniae coli.

82
Q

Hemidesmosome

A

Membrane junctions thatanchor epithelial cells to the basement membranein simple, stratified and pseudostratified epithelia. Also provide anchoring sites for the intermediate filaments of the cytoskeleton.

83
Q

Herring body

A

A dilation along an axon in the posterior lobe of the pituitary caused by the presence of groups of secretory granulesthat containoxytocin or vasopressin.

84
Q

Heterochromatin

A

Acondensed, inactive form of chromatin that stains dark in LM or EM. Located mostly in the periphery of the nucleus.

85
Q

Heterophagy

A

Digestion within a cellof an exogenous substance phagocytosed from the cell’s environment.Involves fusion of phagosome with lysosomes

86
Q

Hilum (Hilus)

A

Adepressionor fissurewhere vessels, nerves and/or ducts enter or leave a bodily organ.

87
Q

Holocrine

A

Form of secretion in which thewhole cell is shed from the gland, usually after becoming packed with the main secretory substance. In mammals, sebaceous glands are one of the few examples.

88
Q

Hyaline

A

Clear, transparent, glassy, granule free, as for example hyaline cartilage, hyaline membrane disease of the lung, and the hyaline zone at the front of a moving amoeba.

89
Q

Hyperplasia

A

The increase in size of a tissue or organ due to increasein the total number of cellspresent, e.g. development of the female breast at puberty due to replication duct epithelium. Contrast with hypertrophy.

90
Q

Hypertrophy

A

Theenlargement or overgrowth of an organor part due to an increase in cell size. May occur along with hyperplasia, as in the pregnant uterus where smooth muscle cell size and cell number both increase.

91
Q

Integrin

A

Family of transmembrane proteins thatattach internally to the cytoskeleton and which also anchor a cell to glycoproteins in the extracellular matrix(laminin, collagen, fibronectin) or on another cell’s surface (e.g. intercellular cell adhesion molecules such as ICAM-1).

92
Q

Intermediate filament

A

Structuralcytoskeleton fibers of intermediate size(~10nm diameter),between microtubules and actin filaments, formed bypolymers of various alpha-helical rod-shaped proteins. Found in many places, including hair, nails, and skin (keratins); muscle Z-disks (desmin); and cell nuclear envelopes (lamins). Unlike microfilaments and microtubules, IFs are extremely stable (they do not ‘cycle’ or ‘treadmill’) and their assembly does not require hydrolysis of ATP or GTP.

93
Q

Intima

A

Innermost, as intunica intima,the innermost layer of blood and lymphatic vessels composed of asimple squamous endotheliumand the immediately surrounding (underlying) connective tissue.

94
Q

Isogenous

A

Literally means “having exactly the same (iso-) genes (-genous)”. Having the same developmental origin; i.e. arising from the same tissue or cell. For example, clusters of 2-4 (or more) chondrocytes thatarose (by mitosis) from the same chondrocyteare known asisogenous groups.

95
Q

Keratin

A

Family of durable intermediate filamentous proteinsproduced but not secretedby epithelial cells; keratin production may be enhanced/induced in response to local wear and tear (e.g. in the vocal cords). Keratins are the primary protein constituents of hair, nails, and thestratum corneum of the epidermis.

96
Q

Kinesin

A

Family ofATP-powered motor proteinsthat transport attached vesicles/particlesalong microtubulesin ananterograde(towards the +-pole) direction. (cf. dynein)

97
Q

Lacteal

A

Lymphatic vessel at the core of an intestinal villus that conveys lipids in chyle (chylomicron-bearing fluid); the name lacteal derives from the fluid’s ‘milky’ appearance.

98
Q

Lacuna

A

(‘Little lake’) -a small space, cavity, or depression. Chondrocytes are chondroblasts that have become trapped by matrix into a lacuna; similarly, osteoblasts become known as osteocytes when they entrap themselves in a lacuna surrounded by bone matrix. (Also recall from embryology that the maternal-blood-filled vascular spaces surrounding the villi in the placenta develop by the fusion of smaller spaces called lacunae.)

99
Q

Lamina propria

A

Layer ofloose (areolar) connective tissueunderlying the epithelium of a mucous membrane

100
Q

Laminin

A

Extracellular matrix glycoproteinfound in the upper (lamina lucida) layer of all basal laminae. Has integrin-, heparan-sulfate- , and dystroglycan-binding domains that allow cells to anchor themselves to the basal lamina. Laminin also binds to the type IV collagen molecules of the lower (lamina densa) layer of the basal lamina, which are themselves involved in securing the basal lamina to the underlyinglamina reticularis.

101
Q

Lamins

A

Group ofintermediate filament proteinsthat form thenuclear laminaon the inner surface of the nuclear envelope. Phosphorylation of lamins leads to breakdown of the nuclear lamina in mitosis. Dephosphorylation leads to binding of chromosomes to vesicles derived from the nuclear membrane, and fusion of these vesicles to reconstitute the nuclear envelope.

102
Q

Lipofuchsin

A

Yellowish-brown pigment that accumulates inresidual bodies (old lysosomes)in long-lived cells; e.g. in liver, kidney, adrenal, cardiac muscle, and/or ganglion cells of older people. Believed to be the oxidized lipid-containing residues of lysosomal digestion.

103
Q

Macula

A

Macula means “spot”, e.g. macula adherens (a desmosome) or macula densa

104
Q

Media

A

Theintermediate layer of blood vessels, composed mostly of smooth muscle cells oriented concentrically around the lumen i.e., tunica media

105
Q

Medulla

A

Theinner portion of an organi.e., medulla of hair follicle, medulla of lymph nodes, medulla of thymus, medulla of suprarenal gland, medulla of kidneys. Compare with cortex.

106
Q

Melanin

A

Manufactured bymelanocytes of skin & hair; made from tyrosine via a series of reactions progressing through 3,4-dihydroxyphenylalanine & dopaquinone in melanosomes

107
Q

Melanosome

A

Ovalvacuoles derived from Golgifound in melanocytes; site of melanin synthesis; tyrosine is transported into melanosomes where tyrosinase and other enzymes convert tyrosine to melanin

108
Q

Merocrine

A

Also called eccrine. Describes a types of secretion where only secretory product is lost from the cell, usually by fusion of secretory vacuole with plasma membrane. Example: parotid gland. Neither the cell membrane nor cytoplasm becomes a part of the secretion.

109
Q

Mesenchyme

A

An embryonic form of connective tissue containing multipotent mesenchymal cells, extensive ground substance and few fibers. Not always derived from mesoderm, but usually is.

110
Q

Mesothelium

A

Simple squamous epithelium of mesodermal origin. It lines the peritoneal, pericardial and pleural cavities.

112
Q

Metachromasia

A

The situation where a stain when applied to cells or tissues gives a color different from that of the stain solution; i.e.,toluidine blue staining mast cell granules reddish purple. Metachromasia usually occurs when a basic stain binds to a polyanion in the specimen so that dye molecules are close enough for interactions to occur between them.

113
Q

Metaphase

A

Classically the second phase of mitosis or of meiosis. In this phase the chromosomesalign themselves on the equator of the mitotic spindle

114
Q

Metaplasia

A

Thechangein the type ofadult cells in a tissue to another normal formbut one that isnot usually found in that location. i.e., pseudostratified ciliated columnar epithelium of the bronchi of heavy smokers can undergo squamous metaplasia, transforming it into stratified squamous epithelium

115
Q

Metastasis

A

The transfer of disease from one organ or part to another not directly connected with it. It may be due either to the transfer of pathogenic microorganisms (for example, tubercle bacilli) or to transfer of cells, as in malignant tumors. The capacity to metastasize is a characteristic of all malignant tumors. Often involves transport of cells via lymphatics or blood vessels.

116
Q

Microtubule

A

Cytoplasmic tubule, 25nm outside diameter with a 5nm thick wall. Made oftubulin heterodimerspacked in a three start helix (or of 13 protofilaments looked at another way) and associated with various other proteins (MAPs, dynein, kinesin). Microtubules of the ciliary axoneme are more permanent than cytoplasmic and spindle microtubules.

118
Q

Microvillus

A

Small finger-like cytoplasmic projectionsemanating from the free surface of the cell into the lumen. Microvilli are one mechanism for increasing cell surface area. Very prominent on some cell (e.g., enterocytes), but present to some extent on most cell types.

119
Q

Mucous

A

Secreting a slimy or mucigenous substance; as the mucous gland. But note that a mucous membrane doesn’t have to secret mucus. Mucous membrane is a synonym for a mucosa.

120
Q

Mucus

A

The secretory product of mucous glands. Avicous mixture of highly hydrated glycoproteins.

121
Q

Nebulin

A

A long nonelastic protein; 2 molecules of nebulin are wrapped around the entire length of each actin thin filament in striated muscle, furtheranchoring it in the Z disk& ensuring the maintenance of the specific array in the sarcomere. Nebulin may help regulate the length of the thin filament in developing muscle.

122
Q

Necrosis

A

Cell death resulting from injury to the cell; in necrosis, the injured cell swells & bursts, cell contents that are toxic to other cells are released into surrounding tissues, & inflammation ensues

123
Q

Neurofilament

A

Intermediate filaments10nm in diameter found in axons of nerve cells

124
Q

Nissl body

A

A mixture offree polysomesinterspersed amongshort stacked cisternae of RER;especially prominent in large motor neurons

125
Q

Node of Ranvier

A

Interruptionsthat occur in themyelin sheathat regular intervals along the length of the axon, exposing the axon; each node indicates an interface between the myelin sheaths of 2 different Schwann cells located along the axon

126
Q

Nucleolar organizer

A

Loops of DNA that transcribe ribosomal RNA.They are located in the acrocentric chromosomes 13-15 and 21; secondary constrictions of the chromosomes where the nucleoli are found in interphase; Since these loci actively transcribe rRNA late into Prophase, they are less coiled and folded, causing them to appear thinner, “constricted,” when viewed cytologically with a microscope at metaphase.

127
Q

Oil red O

A

Stains lipid red

128
Q

Osmium

A

Osmium tetroxide stains unsaturated lipids dark brown or black (also acts as a lipid fixative)

129
Q

Osteoid

A

Thinnoncalcified layer of bone matrixseparating osteoblasts (as well as osteocytes) from mineralized matrix. Consists mainly of collagen type I and other less abundant proteins.

130
Q

Osteon

A

(aka Haversian system). Consists of an Haversian canal with its surrounding concentric lamellaeof bone. Includes osteocytes in lacunae between successive lamellae, and canaliculi that interconnect the lacunae with one another and with the Haversian canal.

131
Q

Paracrine

A

The target cell is located in thevincinity of the signaling cell so that the mediator secreted by the signaling cell travels to the target cell via diffusion rather than in the blood.

132
Q

Parenchyma

A

Thetissue that makes up the essential or specialized part of an organ as opposed to the supporting tissue (stroma).

133
Q

Parietal

A
  1. Of or relating to thewalls of a part or cavity; 2. Parietal Cells are stomach secretory cells which produce HCl and intrinsic factor
134
Q

Pedicel

A

The foot-process of a podocyte that is associated with the outer surface of glomerular capillaries in the kidney. Forms part of the blood-urine filtration barrier.

135
Q

Perinuclear cisterna

A

Thespacewhich separates theinner and outer nuclear membranes. It is continuous with the lumen of the RER cisternae.

136
Q

Periodic acid-Schiff

A

Staining technique whichstains glycogen and most carbohydrate-rich moleculesmagenta. Used to demonstrate basement membranes, g;ycocalyx, glycogen, etc.

137
Q

Periosteum

A

Except at synovial articulations, bone is covered on its external surface with a periosteum which consists of anouter layer of dense fibrous connective tissue and an inner cellular layer containing osteoprogenitor(osteogenic) cells .

138
Q

Peroxisome

A

Small (0.2-1.0 um in diameter),spherical to ovoid membrane-bounded organelles that contain many oxidative enzymes that produce hydrogen peroxide (toxic to cells). Also contain catalase, which breaks down hydrogen peroxide.Function in catabolism of long-chained fatty acids (beta oxidation), forming acetyl coenzyme A as well as hydrogen peroxide by combining hydrogen from the fatty acids with molecular oxygen. Also involved in alcohol metabolism, especially in liver.

139
Q

Phagocytosis

A

The process ofengulfing large particulate matter, such as microorganisms, cell fragments and cells (e.g. defunct red blood cells). Is usually performed by specialized cells known as phagocytes. The most common phagocytes are the white blood cells, the neutrophils and the monocytes. When such monocytes leave the bloodstream to perform their task of phagocytosis, they become know as macrophages.

140
Q

Pinocytosis

A

Transportofsmall substancesin and out of the cellvia vesicles

141
Q

Plasmalemma

A

Theplasma membraneof a cell.

142
Q

Plica

A
  1. A fold or folded part; especially :a groove or fold of skin; 2. Plicae circulares: folds in the small intestines (esp. in the jejunum). Each plica involves both mucosa and submucosa, and carries many villi on its lumenal surface.
143
Q

Polysome

A

One mRNA molecule associated with several ribosomes that are in the process of translating it.

144
Q

Proteoglycan

A

Whensulfated GAGs form covalent bonds with a protein core, they form a family of macromolecules known as proteoglycans, many of which occupy huge domains. Abundant for example in the matrix of hyaline cartilage.

145
Q

Pseudostratified

A

An epithelium in which all cells are in contact with the basement membrane, but not all reach thefree lumenal surface of the epithelium.

146
Q

Pyknosis

A

The characteristic ofcell deathwhereDNA has been enzymatically degradedand the nucleus has become shrunken, heterochromatic and irregular in shape.

147
Q

Retrograde

A

Transport in a reverse or backward direction, e.g., from axon to soma in a neuron. Items returned to the cell body from the axoninclude protein building blocks of neurofilaments, subunits of microtubules, soluble enzymes, and materials taken up by endocytosis.

148
Q

Ruga

A

All the gastric regions display rugae, which arefolds of mucosa and submucosa that disappear in the distended stomach. It permits expansion of the stomach as it fills with food and gastric juices.

149
Q

Sarcolemma

A

Themuscle cell plasma membrane

150
Q

Sarcomere

A

The region between2 successive Z lines. Considered the contractile unit of skeletal and cardiac muscle.

151
Q

Sarcoplasmic reticulum

A

Muscle cells’ smooth endoplasmic reticulum. Forms the terminal cisternae that are part of the triads & diads in striated muscle. Releases calcium into the sarcoplasm to make contraction possible, and also pumps calcium back into the SR cisternae to terminate a contraction.

152
Q

Sebaceous

A

Glands that secrete anoily substance known as sebum in a holocrine fashion. Sebummaintains the suppleness of the skin. They are found throughout the body excepts for the palms of hands, soles of feet, and sides of feet inferior to the hairline.

153
Q

Septum

A

Sheets ofconnective tissue that subdivide an organ (usually incompletely)into smaller compartments

154
Q

Serosa

A

Outer layer of an organ that consists of connective tissue and a mesothelium. Organs with a serosa can be found in all body cavities- peritoneal, pleural, or pericardial.

155
Q

Serous

A

Serous glands secrete awatery fluid that is often rich in enzymes. Contrast with mucous glands, which produce a highly viscous secretion.

156
Q

Sinusoid

A

Wide, highly permeable capillaries in certain organs of the body including bone marrow, liver, spleen and certain endocrine glands.

157
Q

Soma

A

The central portion of a neuronwhere the nucleus and perinuclear cytoplasm are located;also called cell body or perikaryon

158
Q

Squamous

A

Composed ofsingle or stratified layerof tightly packed, flat, low profile polygonal cells. Centrally placed bulging nucleus in each cell.

159
Q

Stereocilium

A

Long branching microvillifound only in the epididymis, vas deferens, and on the sensory hair cells of the cochlea.

160
Q

Striated border

A

Microvilli represent the striated borderof the intestinal absorptive cells.

161
Q

Stroma

A

The elements thatsurround and support the parenchyma of an organ. Usually composed of connective tissue.

162
Q

Synapse

A

Site where nerve impulses are transmittedfrom a presynaptic cell (neuron) to a postsynaptic cell (another neuron, muscle cell, or cell of a gland)

163
Q

Syncytium

A

A multinucleated protoplasmic mass formed by the fusion of previously separate cells, e.g. skeletal muscle or syncytiotrophoblast.

164
Q

Teniae coli (Taeniae coli)

A

Three thick smooth muscle bandsof the outer longitudinal layer of muscularis externa of the colon. Teniae coli are one of the three characteristic features that distinguish large intestine from small (teniae, haustra & epiploic appendages).

165
Q

Terminal bar

A

LM equivalent of a junctional complex (zonula occludens, zonula adherens, and desmosome). Looks like a very small black dot between lateral plasma membranes of neighboring epithelial cells near their apical end.

166
Q

Terminal cisterna

A

Regions of thesarcoplasmic reticulum adjacent to T tubules from which Ca2+ is releasedwhen striated muscle is activated

167
Q

Terminal web

A

Network of actin microfilamentsjust beneath the cell surface. Stabilized by spectrin. In many epithelial cells the microfilaments that form the core of microvilli insert onto the terminal web, and the terminal web in turn inserts on the zonula adherens.

168
Q

Titin

A

Large, linear, elastic protein;four molecules anchor a thick filament between the two Z disksof each sarcomere in striated muscle

169
Q

Trabecula

A

Literally “a beam.” An elongated finger-like projection, often composed of connective tissue and forming part of the stroma of an organ (spleen, lymph node). In the heart trabeculae carneae are composed of cardiac muscle rather than connective tissue.

170
Q

Transcytosis

A

Transport of water-soluble moleculesgreater than 11 nm in diameter from the adluminal plasmalemma to the abluminal plasmalemma or vice versa bypinocytotic vesicles;used by endothelial cells of capillaries, by enterocytes tranporting secretory IgA, etc.

171
Q

Triad

A

T tubule flanked by two terminal cisternae of striated muscle sarcoplasmic reticulum

172
Q

Tropomyosin

A

Part of thin filaments in striated and smooth muscle myofibrilsthat interacts with actin. Prevents interaction of actin and myosin in relaxed muscle.

173
Q

Troponin

A

Associated with tropomyosin and actin on the thin filament in striated muscle; confers Ca2+ sensitivity; 1-1 relationship with tropomyosin; absent in smooth muscle

174
Q

Tubulin

A

Localized in centrosome. Is the main protein component of microtubules.

175
Q

Tunica

A

A coat; ex: tunica intima/media/adventitia of blood vessels

176
Q

Unilocular

A

Having a single droplet or cavity; ex: unilocular fat cell (forms white adipose tissue)

177
Q

Vasa recta

A

Capillaries from efferent glomerular arteriolesthat extend into themedulla and wrap around the limbs of Henle’s loop and the collecting tubule in a hairpin-like shape; descending limb = arteriolae rectae; ascending limb = venae rectae; essential to urine concentration

178
Q

Vasa vasorum

A

Small arteries that enter blood vessel wallsand branch profusely to serve the cells located in the tunica media and tunica adventitia; more prevalent in walls of veins

179
Q

Villus

A

Finger-like projections found on thelumenal lining of the small intestine; serves toincrease the absorbing surface. Consists of a core of lamina propria covered by epithelium.

180
Q

Vimentin

A

Type III intermediate filament protein of the cytoskeleton; found in cells of mesenchymal origin (fibroblasts); secures periphery of Z disks/lines of neighboring myofibrils to each other

181
Q

Visceral

A

Relating to or affecting one or more internal organs. Compare with parietal.

182
Q

Wright’s

A

A type of Romanovsky stain used for differential staining of blood cells; pink=erythrocytes, eosinophil granules; purple=leukocyte nuclei, basophil granules; blue=cytoplasm of monocytes and lymphocytes

183
Q

Z line

A

Line formed where actin filaments attach between two sarcomeres; electron-dense by EM; divides each myofibril into contractile units (sarcomeres) arranged end-to-end

184
Q

Zenker’s

A

Zenker’s fixative=rapid fixative useful light microscopy. Based on a mixture of formalin and mercuric chloride.

185
Q

Zona pellucida

A

Translucent, elastic, noncellular layer surrounding the ovum; present in unilaminar and multilaminar primary follicles, secondary follicles, and graafian follicles

186
Q

Zymogen

A

Inactive precursor of an enzyme, particularly a proteolytic enzyme; contained in secretory vesicles

micro (4 decks)

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