Cytology Summer 2023 M J Valentine PDF

MICROANATOMY CYTOLOGY - CELL STRUCTURE M J Va l e n t i n e B V M S P h D M R C V S D i p l AC V P Lecture plan Cell type and morphology Review of basic cell biology ( review ‘Cytology’ Chapter 1 in Dellman’s Textbook of Veterinary Histology) Key features relevant to veterinary microanatomy CELL MOR...

MICROANATOMY CYTOLOGY - CELL STRUCTURE M J Va l e n t i n e B V M S P h D M R C V S D i p l AC V P Lecture plan Cell type and morphology Review of basic cell biology ( review ‘Cytology’ Chapter 1 in Dellman’s Textbook of Veterinary Histology) Key features relevant to veterinary microanatomy CELL MORPHOLOGY RELATES TO FUNCTION AND TISSUE TYPE Cell shapes: Squamous, cuboidal, columnar, spindle/fusiform, cylindrical, round, polygonal, pyramidal CELLS TISSUE ORGAN Specific function / differentiation e.g. enterocytes, fibrocytes adipocytes, myocytes, neurons Epithelia Connective tissue Nervous tissue Muscle Combination of 4 tissue types Multiple functions CUBOIDAL CELLS Stereocilia Lumen COLUMNAR CELLS Lumen of artery Spindle-shaped (fusiform) cells, with elongated nuclei 1000x Smooth muscle cells of tunica media of artery Uterus A skeletal muscle cell in l. s. NUCLEI CYLINDRICAL SHAPE of cells 1000x Pharynx: Skeletal Muscle Pancreatic Acinar Cells Acinus: the group of cells within the oval Pancreas PYRAMIDAL-SHAPED cells 1000x Pancreatic Acinar Cell Nucleus (DNA) is BASOPHILIC Apical cytoplasm with zymogen granules – enzymes - proteins are EOSINOPHILIC IMPT! H&E, 1000x CELL ORGANELLES Basic constituents of a cell: cytoplasm organelles cell inclusions This Photo by Unknown Author is licensed under CC BY REVIEW CELL BIOLOGY IN CHAPTER 1 breakdown THE NUCLEUS most conspicuous organelle in a cell usually one nucleus in the cell some cells may have more e.g. skeletal muscle cells, osteoclasts, megakaryocytes round, oval, elongated, lobed Image: Liver, hepatocytes. 40X, HE. EXAMPLES OF MULTINUCLEATED CELLS Skeletal muscle cells Osteoclast NUCLEAR PORES ALLOW PASSAGE OF RNA AND PROTEINS INTO THE CYTOPLASM nuclear envelope connects to RER nucleolus produces rRNA DNA RNA PROTEIN Nuclear pores CHROMATIN IS A COMPLEX OF DNA AND PROTEIN Robbins and Cotran, 9th Ed, Fig 1.1 EUCHROMATIN AND HETEROCHROMATIN Electronmicrograph of developing red blood cell (erythroblast) Plasma membrane Mitochondria Nuclear pore Ribosomes Nuclear envelope HETEROCHROMATIN EUCHROMATIN 3 The Most Euchromatic Cells Are: Neurons Hepatocytes (liver cells) Pancreatic acinar cells Sertoli cells Neurons have a large, very pale and round nucleus with a prominent nucleolus (arrow). PLASMA MEMBRANE (Junqueira, 2010) THE PLASMA MEMBRANE EXPRESSES RECEPTORS Both the plasma membrane and the membrane of all organelles constantly express and recycle receptors on both their inner and outer surfaces to perform their functions. All of these molecules are coded for within the genome and they are all produced/processed within the cells by specialized structures. Common pain receptor pathways on a neuron MITOCHONDRIA Self – replicating organelles – Circular DNA molecule from maternal line – Double membrane-enclosed organelle with cristae ATP production Regulated Cell Death (Apoptosis) No ATP  cell death Mitochondrion TEM Cytoplasm FUNCTIONS OF RER (ROUGH ENDOPLASMIC RETICULUM): Amino acid, polypeptide and protein synthesis mRNAcytoplasmic protein GOLGI BODY/APPARATUS (aka GOLGI COMPLEX) Collection of membranebound flattened sacs ‘cisternae’ Modifies and ‘packages’ proteins as secretory granules Golgi body is well developed in secretory cells Antibody secreting plasma cells have prominent areas of cytoplasmic clearing corresponding to the Golgi apparatus Secretory vesicles / granules: LYSOSOMES PROTEASOMES PEROXISOMES SECRETORY VESICLES / GRANULES: LYSOSOMES Membrane-bound dense particles 0.25-0.5 μm Contain hydrolytic enzymes Associated with phagocytosis and autophagy Involved in intracellular digestion Unknown author, quizlet Image: Four lysosomes surrounded by numerous mitochondria. TEM Lysosomes can fuse, degrade and be classified as: primary secondary tertiary = residual bodies = lipofuscin Degradation may result in use of material by the cell, or production of residual bodies. If material remains permanently, is known as lipofuscin (wear and tear pigment). NEUTROPHILS ARE PHAGOCYTES AND CONTAIN LYSOSOMES Blood smear of a mare. No granules/lysosomes are seen in neutrophils stained by routine method. Neutrophil in TEM. Some of electron dense (black) granules are lysosomes. Secretory vesicle / granules: PROTEASOMES Small enzymatic complexes for intracellular digestion of misfolded, damaged or senescent proteins Intracellular digestion in proteasomes requires a protein known as ubiquitin. UBIQUITIN (Lat. ubi – everywhere) is small globular protein present in all eukaryotic cells. Isolated proteasomes, whole mount in TEM Secretory vesicles / granules: PEROXISOMES From: Junqueira, 2010 Contain the enzyme ‘catalase’ which can degrade and produce intracellular hydrogen peroxide Degrade toxic molecules and bacteria in lysosomes and phagosomes Other oxidation reactions for energy production CYTOSKELETON: movement, intracellular transport and shape ULTRASTRUCTURAL = only visible by EM MICROFILAMENTS (actin and myosin) 5-15nm INTERMEDIATE FILAMENTS 6-12nm MICROTUBULES 24nm (Microfilaments) Cytoskeletal elements and cell to cell interactions. Actin and intermediate filaments are involved in cell-cell adhesion and cell shape Robbins and Cotran, 9th Ed, Fig 1.8 SKELETAL MUSCLE Actin and Myosin filaments x. s. 100,000x MICROFILAMENTS ARE INVOLVED IN CELL SHAPE AND INTRACELLULAR MOVEMENT MYOSIN – thick microfilaments – 15 nm in diameter ACTIN – thin microfilaments – 5 - 7 nm in diameter INTERMEDIATE FILAMENTS CHARACTERISE 4 BASIC TISSUE TYPES All organs are composed of these 4 tissues Cytokeratins Epithelium Vimentin Mesenchymal Connective tissue cells Desmin Muscle Neurofilaments Neurons All epithelia Striated and smooth muscle Neurons Detection of intermediate filaments help with identification of cancer cells. cytokeratins (green) in cells of mammary gland carcinoma Fluorescent microscopy MICROTUBULES: intracellular transport Hollow tubes (24nm diam) formed of tubulin dimers Transport of vesicles Chromosome separation Paired tubes (doublets) and dynein arms facilitate cilia (and flagellae) movement iew SURFACE SPECIALIZATIONS Microvilli – very small, absorptive Form a brush/striated border when viewed with the light microscope Stereocilia – larger nonmotile projections, less numerous, absorptive (are considered large microvilli) Cilia – motile projections, longer but less numerous than microvilli -CONTAIN MICROTUBULES Brush border of microvilli (white arrows) Goblet cell PAS STAIN, enterocytes, intestinal mucosa 1000x Microvilli in longitudinal section (contain actin filaments) Microvilli in cross section Electron Micrographs (TEM) Ductus epididymis 1000x Lumen STEREOCILIA (large absorptive microvilli, non-motile) MICROVILLI VERSUS CILIA Microvilli (mv) of enterocytes, brush border of intestinal mucosa, nucleus (n) H&E Cilia (C) of ciliated epithelial and goblet (g) cells respiratory mucosa, H&E CILIA ARE MOTILE BECAUSE OF MICROTUBULES Top v iew CYTOPLASMIC INCLUSIONS: non membrane bound intracellular substances Description Function Common cell/tissue type Haemosiderin Brown granular pigment storage of iron Macrophages in spleen and bone marrow Melanin Brown granular pigment pigment to protect nucleus Epidermis Uvea from UV rays found in epidermis Lipofuscin Brown granular pigment ‘wear and tear’ found in post mitotic cells of older animals Myocardiocytes Neurons Lipid Large single clear space in adipocytes, washed out during routine processing (white fat). Multiple small spaces of in cytoplasm with abundant mitochondria Storage of energy, insulation (white fat) Heat production (brown fat) Adipocytes in subcutaneous tissue and abdominal fat deposits Glycogen Patchy clear spaces Storage of glucose Hepatocytes, skeletal muscle and neurons 1 Pigment melanin 2 3 Lipid droplet Glycogen inclusions in hepatocytes 4 Brown fat vs White fat Hemosiderin Hematoxylin and eosin Perls Prussian Blue stain for Iron Spleen. Iron stain is used to differentiate it from other intracytoplasmic pigments Myocardium: LIPOFUSCIN granules Slide 25 1000x Cardiac Muscle EXTRA EXTRARESOURCES RESOURCES https://xvivo.com/blog/activate-inhibit-cilia-flagella-move/ https://ohiostate.pressbooks.pub/vethisto/front-matter/introduction/