* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Notes
Survey
Document related concepts
Signal transduction wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Extracellular matrix wikipedia , lookup
Tissue engineering wikipedia , lookup
Cell growth wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell culture wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cellular differentiation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Endomembrane system wikipedia , lookup
Cell nucleus wikipedia , lookup
Transcript
HISTOLOGY AND HEMATOLOGY CYTOLOGY Learning objectives i. At the head of this section you should; ii. Know the fine structures of the cell. iii. Know the valius organell and their functions. The cell is the smallest unit of living matter of a multi-cellular living organism. Shape, structure and size of cells vary with the specific functions of the cells. There are spherical, oval, columnar, cuboidal and squamous cells. Some cells are spindle shaped; others are star shaped (stellate) with numerous cytoplasmic processes. Changes in activity are associated frequently with changes in shape (e.g., from squamous to cuboidal or cuboidal to columnar). Pronounced differences in cell size exist, varying from cells observable only at the highest level of magnification of the light microscope (LA1) (e.g., microglial cells) to those visible with the naked eye, such as the mature oocytes. STRUCTURAL ORGANIZATION OF THE CELL The various functions of the organism are reflected in the structural organization of the cells that perform these functions. Thus, cells whose primary function is protein synthesis possess a well-developed rough-surfaced endoplasmic reticulum (ER) and-or polyribosomes and those with high secretory activity characteristically have a large Golgi apparatus. However, in spite of these differences, all cells have the same general structural organization, consisting of a nucleus and surrounding cytoplasm in which are found the various organelles (Fig. 1-1). The cell is the smallest unit of living matter of a multi-cellular living organism. Shape, structure and size of cells vary with the specific functions of the cells. There are spherical, oval, columnar, cuboidal and squamous cells. Some cells are spindle shaped; others are star shaped (stellate) with numerous cytoplasmic processes. Changes in activity are associated frequently with changes in shape (e.g., from squamous to cuboidal or cuboidal to columnar). Pronounced differences in cell size exist, varying from cells observable only at the highest level of magnification of the light microscope (LA1) (e.g., microglial cells) to those visible with the naked eye, such as the mature oocyte Nucleus 1 Because the structural organization of the nucleus varies during the different phases of cell life, the following description applies only to the nucleus as it appears between two cell divisions, i.e., the interphase nucleus during the duplication phase. Nuclear configuration and size vary considerably in different cell types. The nucleus is usually spherical in cuboidal cells, whereas an elongated ovoid nucleus is common to columnar and spindle-shaped cells. Other cells have bean- or kidney-shaped nuclei, common to monocytes, or multi lobulated and horseshoe-shaped nuclei, characteristic of neutrophilic (polvmorphonuclear) leukocytes. Although most cells of the mammalian organism have only one nucleus, it is not unusual to find bi- or even multinucleated cells such as those in liver (hepatocytes) and bone (osteoclasts). The nucleus consists of chromatin embedded in the nucleoplasm and is bounded by the nuclear envelope. One or more nucleoli may be present, depending on the degree of differentiation. NUCLEAR ENVELOPE The nuclear envelope cannot always be clearly distinguished with the light microscope. The nuclear envelope is pierced by numerous circular "pores" around which are fused the two nuclear membranes. The pores are closed by-a thin septum. It is believed that the pores play a role in the exchange of material between the nucleus and the cytoplasm. CHROMATIN Chromatin is dispersed within the nucleo-plasm. It is deoxyribonucleic acid (DNA) combined with histones and other structural proteins. Chromatin forms highly coiled, long strands, too fine to be detected with the light microscope. However, it is designated heterochromatin when portions of the chromatin strands condense or clump in a given area, and is readily detected with the light microscope as dark clumps or particles located on the inside of the nuclear envelope or in the vicinity of the nucleolus. The remaining empty-appearing spaces are filled with diffuse chromatin or euchromatin .There are two sex chromosomes designated X chromosome and Y chromosome. Cells from male animals have one X and one Y chromosome, whereas cells from females have a pair of X chromosomes. 2 Granular vesicle Golgi (secretory apparatu granule) s Nuclear pore Nuclear Centriol e envelope • Mitochondri on Basement membrane Granular endoplasmic reticulum FIG. 1-1. Schematic drawing of the general organization of a cell. 3 NUCLEOLUS The nucleolus is a conspicuous, spherical, basophilic body that functions in the synthesis and assembly of RNA It consists of anastomosing strands of compact filaments associated with RNA granules the size of ribosomes in a meshwork of filaments. Cytoplasm Cell organelles and cell inclusions are embedded in the cytoplasmic matrix or hyaloplasm. In spite of its structure less appearance, the cytoplasmic matrix is an important part of the cell because it consists of polypeptides, proteins, enzymes, ions and water. ORGANELLES The organelles are variously organized structures that function in cell metabolism. They are;(1) The cell membrane, (2) Granular endoplasmic reticulum, (3) a granular endoplasmic reticulum, (4) Golgi apparatus. (5) Mitochondria. (6) Lysosomes (7) Centrioles. The cell inclusions are:(1) Microfilaments, (2} microtubules, (3) Glycogen, (4) Lipid, (5) Yolk. This is a SAMPLE (Few pages have been extracted from the complete notes:-It’s meant to show you the topics covered in the full notes and as per the course outline Download more at our websites: www.naarocom.com To get the complete notes either in softcopy form or in Hardcopy (printed & Binded) form, contact us on: Call/text/whatsApp +254 719754141/734000520 Email: [email protected] [email protected] [email protected] Get news and updates by liking our page on facebook and follow us on Twitter 4 Sample/preview is NOT FOR SALE 5