Animal Organization, Hematology, & Cell Cycle PDF

ANIMAL ORGANIZATION, INTRODUCTION TO HEMATOLOGY, & CELL CYCLE Sameh Sarray, PhD Department of Medical Biochemistry Animal Organization ■ Cells → Tissues → Organs → Organ System → Organism ■ Tissue types – Epithelial tissue – Muscular tissue – Nervous tissue – Connective tissue Epithelial tissue-...

ANIMAL ORGANIZATION, INTRODUCTION TO HEMATOLOGY, & CELL CYCLE Sameh Sarray, PhD Department of Medical Biochemistry Animal Organization ■ Cells → Tissues → Organs → Organ System → Organism ■ Tissue types – Epithelial tissue – Muscular tissue – Nervous tissue – Connective tissue Epithelial tissue- classification ■ According to layer: – Simple (one layer) – Stratified (multiple layers) ■ According to shape – Squamous (Flat) – Cuboidal (squared cube) – Columnar (long) ■ Special variants: – Pseudostratified (appears multi layered but actually one layer) – Transitional (can stretch and change shape) ■ Found in bladder, urethra, and ureters ■ In full bladder, transitional epithelia can flatten out and resemble squamous cells ■ Surface Modifications: – Microvilli – Cilia – Stereocilia No. Epithelial Tissue location 1. Simple squamous mouth, blood vessels and lungs 2. Simple cuboidal glands, duct and portions of the kidney tubules 3. Simple columnar lining of the intestine and gallbladder Pseudostratified 4. columnar line the nasal cavity, bronchi and trachea skin surface, lining of the mouth, throat 5. Stratified squamous and esophagus 6. Stratified columnar mammary ducts and epididymus 7. Transitional urinary bladder, renal pelvis and ureters Muscular tissue ■ Is a soft tissue that forms the various types of muscles allowing them to contract. ■ Three types: – Skeletal – Smooth – cardiac Skeletal muscles ■ Attached to bone ■ Contraction is voluntary (under conscious control) ■ With striation, arrangement of contractile filaments (actin, myosin filaments). ■ Nuclei at tubular cell periphery Striated skeletal muscle cells in microscopic view. The myofibers are the straight vertical bands; the horizontal striations are the arrangement of contractile filaments. The cigar-like dark patches beside the myofibers are muscle-cell nuclei Smooth muscles ■ Visceral muscles ■ Make up the wall of internal organs – Intestine – Blood vessels ■ Spindle shape ■ Contraction is Involuntary ■ Non-striated ■ They contain nuclei Cardiac muscles ■ In the Heart. ■ Involuntary contraction ■ Striated ■ Nucleated ■ Branched and bound together by intercalated disks: This arrangement aids in communication between muscle fibers Nervous tissue ■ Is the component of 2 major parts of the nervous system: the central nervous system (Brain & spinal cord) and peripheral nervous system ( the nerves that branch out from the brain and spinal cord. These nerves form the communication network between the CNS and the body parts.) ■ Two types: ■ ■ Neurons: are the structural and functional unit of the nervous system. They help in transmitting the nerve impulse. Neuroglia: are the supporting cells. ■ Neuron consists of: ■ Cell body (soma): contains nucleus, cytoplasm, organelles. ■ Dendrites: transmit signals from other neurons to cell body ■ Axon: takes nerve impulses away from cell body toward the target cells Nervous tissue Connective tissue ■ "connective tissue" is a term given to several body tissues that connect, support, and help bind other tissues. ■ is composed primarily of an extracellular matrix and a limited number of cells. ■ Five classes: 1. Loose & dense connective tissue 2. Adipose tissue 3. Cartilage 4. Bone 5. Blood Bones ■ Compact bone: is constructed in complex cylindrical units called Haversian or osteonic system which are arranged next to each other and are cemented together with matrix material ■ Central (Haversian) canals run longitudinally. Blood vessels and nerves. - around central canals are concentric lamella - osteocytes occupy lacunae which are between the lamella - radiating from the lacunea are channels called canaliculi Traverse section of bone Cartilage ■ Found at bone ends, trachea. ■ Is a strong, flexible connective tissue that protects bones against bone friction. ■ It acts as a shock absorber ■ t is made up of cells called chondroblasts and chondrocytes and extracellular matrix ■ Lacunae: are spaces in which bone cells are present. The role of lacunae is to provide a home for the cells it contains while also keeping them alive and functional. In bones, lacunae encase osteocytes; in cartilage, lacunae enclose chondrocytes. A section of hyaline cartilage, showing the chondrocytes trapped in lacunae in the matrix Adipose ■ Beneath skin, around kidneys and heart ■ Functions: isolation, cushioning, fat storage, protection Blood Erythrocytes ■ As a connective tissue, it consists of cells suspended in an intercellular matrix (plasma). ■ Blood is the only liquid tissue in the body The activities of the blood may be categorized as: ➢ Transportation: Carrying oxygen and nutrients to the cells; Transporting carbon dioxide and nitrogenous wastes from the tissues to the lungs and kidneys; Carrying hormones from the endocrine glands to the target tissues. ➢ Regulation: regulate body temperature by removing heat from active areas and transporting it to other regions or to the skin where it can be dissipated; Functioning in pH regulation through the action of buffers in the blood. ➢ Protection: Preventing fluid loss through hemorrhage when blood vessels are damaged due to its clotting mechanisms; Helping (phagocytic white blood cells) to protect the body against microorganisms that cause disease by engulfing and destroying the agent. Protecting (antibodies in the plasma) against disease by their reactions with offending agents Leukocytes Fluid with protein Matrix Hematology Blood Formed Elements Red Blood Cells (Erythrocytes) White Blood Cells (Leukocytes) Plasma Platelets Thrombocytes Water Proteins Salts wastes Plasma ■ Liquid suspension ■ Yellowish ■ 55% of blood volume ■ Contains: (Water, Proteins, Salts, Wastes, Clotting Factors) ■ Serum: blood plasma without clotting factors (fibrin) Erythrocytes (RBCS) ■ Numerous ■ 120 days life span ■ Biconcave discs, Un-nucleated, no Mitochondria ■ Filled with hemoglobin ■ Primary function: Transportation of oxygen Leukocytes (WBCs) ■ Have nuclei and mitochondria. ■ Can move from capillaries to tissue by an amoeboid type of movement ■ Aid in defense and immunity. ■ Invisible if not stained. ■ Based on the presence and absence of microscopic granules in their cytoplasm when stained with Giemsa or Leishman stains, they can be classified as: ■ Granulocytes (Neutrophils, Eosinophils, Basophils ) ■ Agranulocytes (Lymphocytes, Monocytes) Granulocytes: ■ Multilobular nucleus (polymorphnuclear). ■ Classification based on granules staining: – Neutrophils (pink color tiny granules very difficult to see, Nucleus is multi-lobed (2-5 nuclear lobes) with lobes connected by thin strands of nuclear material, capable of Phagocytizing foreign cells, toxins, viruses) – Eosinophils (large granules appear pink or red color granules, Nucleus has two lobes connected by a band of nuclear material. Effective against parasitic worms and allergic responses) Basophils (the granules are large stain deep blue to purple and are often so numerous they mask the nucleus . Theses granules contain histamines (cause vasodilation) and heparin (anti-coagulant – Agranulocytes: ■ Mononuclear cells (one nucleus). ■ Two types: Monocytes: -The nucleus is most often "U" or kidney bean shaped; - The cytoplasm is abundant and light blue -These cells leave the blood stream (diapedesis) to become macrophages. (In tissue they are called macrophages ) -As a monocyte or macrophage, these cells are phagocytic and defend the body against viruses and bacteria. Lymphocytes: (B cells, T cells ) - Nucleus is very large for the size of the cell and stains dark purple, leaving a very thin rim of cytoplasm. - These cells play an important role in our immune response. - The T-lymphocytes act against virus infected cells and tumor cells. The B-lymphocytes produce antibodies. monocyte Platelets -thrombocytes ■ are cell fragments of large cells found in the bone marrow ■ They are the smallest formed element in the blood ■ Lacks nuclei ■ Limited life span of few days ■ Important for blood clotting Cell division ■ Cell Division: process by which a cell divides to form two new cells (daughter cells) ■ Important terms (review your booklet): chromosome, chromatid, chromatin, centromere, haploid, diploid) ■ Three types of cell division, or cell reproduction – Prokaryotes (bacteria) ■ Binary fission→ divides forming two new identical cells – Eukaryotes ■ Mitosis – – ■ Cell or organism growth Replacement or repair of damaged cells Meiosis – formation of sex cells, or gametes Cell cycle ■ The cell cycle is divided in 2 stages: interphase and mitotic phase ■ interphase is divided into 3 stages: G1, S, and G2 – G1 phase → Cells grows and decision to divide is take – S phase → DNA replication occurs (at this time each chromosome doubles so that it contains two sister chromatids joined at the centromere) – G2 phase → preparation for cell division is complete and the cell enters the brief M phase ■ M phase: cell division (1-2 Hours) ■ Full cell cycle 18-24 Hours Cell Cycle (cont.) ■ Mitosis: – 1 parental cell divides to into 2 daughter cells (2N diploid cells) ■ daughter cells are identical to parental cells – Occurs in somatic cells – 4 stages: prophase, Metaphase, Anaphase and Telophase. Mitosis (Prophase): 1. 2. 3. 4. 5. Chromatin condenses into Chromosomes Nuclear envelope fragmented Early mitotic spindle Chromosomes duplicates to 2 sister chromatids. Chromatids held by centromere Mitosis (metaphase): 1. chromosomes line up at the center (metaphase plate) 2. Centromere is attached to two spindle fibers Mitosis (anaphase): ■ Centromeres divide (each chromatid one centromere) ■ Chromatids are called chromosomes ■ Migration of chromosomes toward opp. Pole. Mitosis (telophase): ■ Formation of nuclear envelope around daughter chromosomes ■ Chromosomes diffuse to chromatin ■ Nucleolus appears in new nucleus ■ Cytokinesis occur (division of cytoplasm) Meiosis ■ Meiotic cell division occurs in germ cells of all living cells ■ During meiosis, the genetic material of a diploid germ (2N) cell undergoes two nuclear divisions and resulting into four haploid daughter cells. ■ There are 2 successive nuclear division in meiosis: – Meiosis I: called also Reductional division – Meiosis II : equational division ■ Before a dividing cell enters meiosis, it undergoes a period of growth (interphase) Meiosis I: ■ Meiosis I separate homologous chromosomes and produce 2 cells with haploid chromosomes number (N) for that reason is called reductional division ■ Meiosis I consist of 4 stages: – Prophase I – Metaphase I – Anaphase I – Telophase I Homologous chromosomes are paired chromosomes. They have the same gene sequence, loci, chromosomal length, and centromere location. Although they may have the same genetic sequence and loci, they may differ in alleles. The homologous pair is comprised of a paternal chromosome and a maternal chromosome Prophase I ■ Chromatin condensation and the chromosomes become visible). ■ Increase in the nuclear volume ■ Nucleolus disappears & Nuclear envelope break down ■ pairing between homologus chromosomes (called synapsis) ■ Crossing over of genetic material between two homologous chromosomes (DNA recombination) Metaphase I ■ The centrioles migrate away from one another; The spindle apparatus is formed ■ Each chromosome, consisting of two chromatids, lines up side-by side with its homolog ■ Tetrads (4 sister chromatids) align along equator Anaphase I ■ Movement of chromosomes to the opposite poles. ■ A difference between mitosis and meiosis is that the sister chromatids remain joined after metaphasis, whereas in mitosis they separate Telophase I ■ Nuclear envelope organized around 2 groups of chromosomes ■ The nucleolus reappears ■ Cytokinesis involves the formation of a cleavage furrow resulting in the pocketing of the cell into two cells ■ At the end of telophase, 2 daughter cells are produced each with one half of the number of chromosomes ■ Interkinesis (interphase II) is similar to interphase Meiosis II: ■ Is the second part of the meiotic process it consists of prophase II, metaphase II, anaphase II and telophase II ■ Prophase II – Chromatin condensation (Chromosomes visible). – Nucleolus disappears – Nuclear envelope break down ■ Metaphase II: Each chromosome, consisting of two chromatids, lines up at metaphase plate (equator). ■ Anaphase II: Division of centromere (Chromatids separation) and migration of individual chromatid to opposite poles. ■ Telophase II – Nuclear Envelope at each pole – Nucleolus appears in new nucleus – Cytokinesis occur (division of cytoplasm) and four haploid gametes are formed END