Histology 2024/2025 Past Paper - Cell Biology PDF

HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday The Cell SECTION 1: CELL AND CYTOPLASM SECTION2: CELL CYCLE Light and Transmission Electron Microscopy  Microscopic techn...

HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday The Cell SECTION 1: CELL AND CYTOPLASM SECTION2: CELL CYCLE Light and Transmission Electron Microscopy  Microscopic techniques: histochemical, immunocytochemical and staining techs., showed sub cellular elements called organelles. CELL AND CYTOPLASM  Cells maintain proper homeostasis of the body  Structural features are common to all cells 1) CELL MEMBRANE  Consists of phospholipid bilayer and integral transmembrane membrane proteins  Peripheral membrane proteins located on external and internal cell surfaces  Peripheral proteins attached to microfilaments of cytoskeleton  Transmembrane proteins are located within lipid bilayer of the cell membrane  Transmembrane proteins transport molecules across lipid bilayer  Cholesterol molecules within the cell membrane stabilize the cell membrane 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday  Carbohydrate glycocalyx covers cell surfaces (ex. Microvilli) in specialized absorptive cells, kidney  Glycocalyx important for cell recognition, cell adhesion, and receptor binding sites MOLECULAR ORGANIZATION OF CELL MEMBRANE  Lipid bilayer is in fluid state, for this reason the fluid mosaic model (stucture of cell membrane).  Phospholipids form two layers with polar heads facing inner and outer surfaces. Nonpolar tails are in center of membrane. CELL MEMBRANE PERMEABILITY AND TRANSPORT  Cell membrane shows selective permeability and forms a barrier between internal and external cell environments  Permeable to oxygen, carbon dioxide, water, steroids, and lipid-soluble chemicals  Larger molecules enter cell by specialized transport mechanisms: Endocytosis is ingestion of extracellular material into the cell Exocytosis is release of material from the cell Pinocytosis is ingestion of extracellular fluid into the cell Phagocytosis is uptake of large, solid particular substance into the cell 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday Receptor-mediated endocytosis involves pinocytosis or phagocytosis via receptors on cell membrane and formation of clathrin-coated pits. ⇨ Uptake of low-density lipoproteins and insulin as example of receptor-mediated endocytosis. 2) CELLULAR ORGANELLES Membrane bound: nucleus, mitochondria, endoplasmic reticulum, Golgi complex, lysosomes, and peroxisomes Nonmembrane bound: ribosomes, basal bodies, and centrosomes Mitochondria  Surrounded by cell membrane  Shelflike cristae in protein-secreting cells and tubular cristae in steroid secreting cells  Present in all cells, except mature red blood cells, and is especially numerous in highly metabolic cells  Produce high-energy ATP molecules  Cristae contain respiratory chain enzymes for ATP production  Matrix contains enzymes, ribosomes, and circular mitochondrial DNA  Arise from preexisting mitochondria by growth and division Rough Endoplasmic Reticulum  Exhibits interconnected cisternae that are covered with ribosomes  Highly developed in protein-synthesizing cells  Synthesizes proteins for export or lysosomes 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday  Synthesizes integral (essential) membrane proteins and phospholipids for cell membrane  Free ribosomes synthesize proteins for cell cytoplasm Smooth Endoplasmic Reticulum  Devoid of ribosomes and consists of anastomosing tubules  Found in cells that synthesize phospholipids, cholesterol, and steroid hormones  In liver cells, proliferates to deactivate or detoxify harmful chemicals  In liver cells is involved with carbohydrate metabolism and converts glycogen to glucose  In skeletal and cardiac muscle fibers, stores and releases calcium between contractions Golgi Apparatus  Present in all cells, except mature red blood cells  Consists of stacked, curved cisternae with convex side as the cis face  Mature concave side is the trans face  New synthesized protein transported in transfer vesicles to Golgi apparatus  Cisternae modify enzymes and sort and package proteins  Adds sugars to proteins and lipids to form glycoproteins, glycolipids, and lipoproteins  Secretory granules are modified, sorted, and packaged in membranes for export outside of cell or for lysosomes  Other proteins and phospholipids are incorporated into cell membrane 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday Ribosomes  Appear as free or attached (as to endoplasmic reticulum)  Most abundant in protein-synthesizing cells  Decode genetic messages from nucleus for amino acid sequence of protein synthesis  Free ribosomes synthesize proteins for cell use  Attached ribosomes synthesize proteins that are packaged for export or lysosomes use Ribosomal subunits synthesized in nucleolus and transported Lysosomes  Membrane-bound vesicles filled with hydrolyzing or digesting enzymes called acid hydrolases ⇨Synthesized in rough endoplasmic reticulum and packaged in Golgi apparatus  Separated from cytoplasm by membrane to prevent damage to cell  Functions in intracellular digestion or phagocytosis  Digest microorganisms, cellular debris, worn-out cells, or cell organelles  Residual bodies seen after phagocytosis  Very abundant in tissue macrophages and white blood cells neutrophils Peroxisomes  Contain oxidases that form cytotoxic hydrogen peroxide  Contain enzyme catalase to eliminate excess hydrogen peroxide  Abundant in liver and kidney cells, which remove much of the toxic material  Detoxify, degrade alcohol, oxidize fatty acids, and metabolize compounds 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday 3) CELL CYTOSKELETON: definition ? A) Microfilaments  Thinnest microfilaments in the cytoskeleton  Composed of protein actin and contribute to cell and organelle movements  Distributed throughout cell and used as anchors at cell junctions  Form core of microvilli and terminal web(net) at cell apices  Actin–myosin interactions produce muscle contractions B) Intermediate Filaments  Thicker than microfilaments  Epithelial cells contain keratin filaments  In skin cells, they terminate at desmosomes and hemidesmosomes  Vimentin filaments found in mesenchymal cells  Desmin filaments found in smooth and skeletal muscles  Glial filaments found in astrocytic cells of the nervous system  Lamin filaments found in nuclear membrane C) Microtubules  Largest filaments in cytoskeleton and found in most cells except red blood cells  Composed of α and β tubulin  Originate from centrosome  Determine cell shape and function in intracellular transport  Form spindles and separate duplicated chromosomes during cell mitosis  Present in cilia, flagella, centrioles, and basal bodies 4) Centrosome and Centrioles  Centrosome located near nucleus and contain two centrioles 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday  Major microtubule-forming center and mitotic spindles  Centrioles perpendicular (vertical) to one another; contain nine clusters of three microtubules each arranged in a circle  Before mitosis, centrioles replicate  During mitosis, centrioles form mitotic spindles to control distribution of chromosomes  Centrioles induce formation of basal bodies and microtubules in cilia and flagella  CYTOPLASMIC INCLUSIONS Temporary structures such as lipids, glycogen, crystals, and pigment  NUCLEUS AND NUCLEAR ENVELOPE  Nucleus contains chromatin, nucleoli, nuclear matrix, and cellular DNA  Double membrane called the nuclear envelope surrounds the nucleus  Nucleolus is not membrane bound  Outer membrane of nuclear envelope contains ribosomes and is continuous with rough endoplasmic reticulum  Nuclear pores at intervals (gaps) in the nuclear envelope.  Nuclear pores control movements of material between nucleus and cytoplasm  SURFACES OF CELLS Junctional Complex  Zonula occludens or tight junctions form an effective epithelial barrier 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday  Transmembrane proteins claudin fuse the outer membranes of adjacent cells to form tight junctions  In zonula adherens or adhering junctions, transmembrane proteins attach to cytoskeleton and bind adjacent cells  Actin filaments attach zonula adherens  Desmosomes are spotlike structures, very well-known in skin and cardiac cells Junctional Complex  Desmosomes anchor cells through extension of transmembrane proteins into intercellular space between adjacent cells  Desmosomes bound to intermediate filaments  Hemidesmosomes are present at base of epithelial cells to prevent separation from connective tissue layer, as in basal layer of skin  Gap junctions are spot like structures with fluid channels called connexons  Ions and chemicals diffuse through connexons from cell to cell  Gap junctions allow rapid communications between cells for synchronized action Basal Regions of Cells  the basal region or the base of epithelial cells: ► are attached to a thin, moderately electron-dense layer called the basal lamina The basal lamina is seen only with the electron microscope. Basal lamina and the reticular fibers of connective tissue are recognized under the light microscope as a basement membrane. 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday Infolded Basal Regions  Infolded basal and lateral cell membranes function in ionic transport  Found in kidney and salivary gland cells  Na+/K+ ATPase (sodium pumps) embedded in infolded membranes  Numerous and long mitochondria in infoldings supply ATP for ion transport Cilia  Motile apical surface modifications that are inserted into basal bodies.  Line cells in the respiratory organs, uterine tubes, and efferent ducts.  Motility caused by sliding microtubule doublets  Motor protein dynein uses ATP to move cilia Microvilli  Well developed in small intestines and kidney  Main function is absorption of nutrients from intestines and glomerular filtrate Section 2: Cells and the Cell Cycle CELL POPULATIONS IN ADULTS  Permanent—nerve and muscle cells are not replaced when damaged  Stable cell population—liver cells can proliferate to replace removed or damaged cells  Renewing cell population—skin, gastrointestinal organs, blood cells in red bone marrow, and germ cells in testes are constantly replaced 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday CELL CYCLE: INTERPHASE AND MITOSIS  Divided into interphase and mitosis  Interphase is prolonged and consists of different phases that replicate cell contents. ex. cell size and its contents increas: DNA, centrioles, and chromosomes replicate, and the cell prepares for division (mitosis).  Mitosis consists of four phases : prophase, metaphase, anaphase, and telophase. MITOSIS: 1)Prophase  Condensation of chromosomes to form two identical chromatids  Chromatids are joined together at the centromere  Nuclear envelope and nucleolus disappear  Centrosome divides, and centrioles move to the opposite poles of the cell  Centrioles form microtubules of the mitotic spindle  Microtubules attach to kinetochores of chromatids and align chromosomes in the middle of the cell 2)Metaphase  Chromosomes highly condensed  Kinetochore lines up chromosomes along the equator of the cell formation of equatorial plate 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday 3)Anaphase  Chromatid pairs separate at the centromere because of enzymatic action and become chromosomes  Chromosomes migrate to opposite poles of the cell because of shortening of kinetochore microtubules  Migrating chromosomes form a V shape in the cell  Cleavage groove appears at the cell equator 4)Telophase  Terminal phase of mitosis  Chromosomes complete their migration to the opposite side of the mitotic spindle  Chromosomes condense to form chromatin of the interphase cell  Nucleolus reappears, and a nuclear envelope is formed  Contractile ring becomes the site of cleavage for separation of daughter cells  Cytokinesis is the division of genetically identical cells during mitosis MEIOSIS  Specialized cell division restricted to male and female germ cells  Produces ova and sperm with a haploid number (23) of chromosomes  Recombination of genes occurs at fertilization of ovum by sperm Refereces: Title: Atlas of histology with functional correlations Victor P. Eroschenko. 2ed lecture HISTOLOGY 2ed year 2024/2025 BSc MEDICAL Lab. SCIENCES Wadi Alshatti University 7/11/2024, Thursday : ‫ فقط تعرفوا ع البيانات‬،‫ال تقوموا بطباعة هذه الصور‬ Mitochondria (longitudinal and cross section). ×49,500 Rough endoplasmic reticulum. ×32,000. lysosomes and residual bodies in the cytoplasm ×16,000. 2ed lecture