Stem Cells and Tissues PDF

Stem cells and tissues  **MLO15.**    Distinguish between key cell types found within the body and understand how cells form the building blocks of organs and tissues and relate this to how the body functions as a whole. Every cell in the human body is derived from another cell. The embryo develop...

Stem cells and tissues  **MLO15.**    Distinguish between key cell types found within the body and understand how cells form the building blocks of organs and tissues and relate this to how the body functions as a whole. Every cell in the human body is derived from another cell. The embryo develops through the fusion of egg and sperm, and then through a process of cell division. Stem cells are undifferentiated cells that are able to differentiate into specialised cell types. Properties of stem cells that differentiate themselves from other somatic cells: - Ability to self renew on an almost unlimited basis (asymmetric cell division) - Can differentiate into multiple cell types There are four different types of stem cells: - Totipotent: can become any cell type in the developing embryo and form structures of the placenta, can replicate in unlimited numbers without losing their total potency - Pluripotent: can differentiate into almost any cell in the body, potency is lost over time and they can only become certain types of cells - Multipotent: Self renew for long periods of time and differentiate into specialised cells with specific functions, limited in ability to differentiate, differentiation occurs in bone marrow - Induced/induced pluripotent: biologically engineered to have al the characteristics of pluripotent stem cells Totipotent stem cells: - Formed soon after egg and sperm fuse - Capacity to have almost unlimited differentiation capacity without losing potency - Derived from foetal tissue - Huge therapeutic value - Limited availability as they can only be derived from early embryonic tissue Pluripotent stem cells: - Can differentiate into almost any cell type - Limited availability as derived from inner cell mass of early embryo - Huge therapeutic value - Ethical issue as derived from embryo Multipotent stem cells - Very limited differentiation capacity - Advantage can be isolated directly from adult tissue - Difficult to isolate however because only a small number of stem cells within that particular tissue - As derived from patients, no problems with rejection of tissues - Eg. Haematopoietic stem cells: found in bone marrow, differentiate into all different cell types in the blood Haematopoietic stem cells: - Can differentiate down to lineages, cell lineages, pathways - Common myeloid progenitor cells differentiated into all the red blood cells or erythrocytes and all the platelets - All the immune cells which are classified as granulocytes, so things like neutrophils and eosinophils and mast cells and monocytes and macrophages - Whereas common lymphoid progenitor cells differentiate down a slightly different, cellular pathway, and they form all the different sorts of lymphocytes Induced pluripotent stem cells - Derived from adult tissues - Eg. Fibroblasts: derived from skin, grown in cell culture in mix of growth factors, enables fibroblasts to differentiate into pluripotent stem cells - IPSCs have same functions as embryonic stem cells without ethical issues - Huge therapeutic value A tissue is a group of cells that carry out a specific function - In physiology, is a level of organization in multicellular organisms, it consists of a group of structurally and functionally similar cells and their intracellular material An organ, in biology, is a group of tissues that have been adapted to perform a specific function There are 4 types of tissue found in the human body: - Connective: support other tissues and cells, connect and differentiate between two organs and tissues - Epithelial: covering of different organs and tissues - Muscle: movement and motor function - Nervous: control what organs and tissues do Gastrula (germ layer) formed of three layers: - Endoderm (inner): lung cell, thyroid cell, digestive cell - Mesoderm (middle): cardiac muscle, skeletal muscle, tubule cell, RBC, smooth muscle - Ectoderm (outer): skin cell, neuron, pigment cell A diagram of skin cells Description automatically generated with medium confidence Epithelial tissue: a sheet of cells that cover a tissue surface, line a cavity or form glandular structures - Protection - Secretion - Absorption - Transport - Ion filtration - Detection of sensation - Mucous production Epithelium has a continuous cell layer - Skin -- lung -- mouth -- intestine -- salivary gland -- urinary tract - Single layer - Composed entirely of epithelial cells - Apical surface (luminal) - Basal surface - Cell junctions (tight, desmosomes, gap) - Underlying basement membrane (reticular connective tissue) - Underlying connective tissue (nerves, capillaries)  Simple squamous: - Single layer of flattened cells, disc shaped central nuclei - Adapted for diffusion/filtration - Secretes lubricating substance in serous membranes Stratified squamous: - Several layers thick, basal cells are cuboidal or columnar and metabolically active, surface cells are squamous - Keratinized: dead surface cells full of keratin - Basal: undergo mitosis - Protects underlying tissues in areas subjected to abrasion Stratified cuboidal: - 2 layers of cuboidal cells - Protection Pseudostratified columnar: - Single layer of cells with differing heights, nuclei at different levels - May have goblet cells and cilia - Secretion of mucus, propulsion of mucus by ciliary action Simple cuboidal: - Single layer of cuboidal cells, large spherical central nuclei - Secretion and absorption, can be active and pump products or passive Simple columnar: - Single layer of tall cells, round to oval nuclei - May have cilia and goblet cells - Absorption, secretion of mucus, enzymes and other substances, ciliated type propels mucus Transitional: - Mix of all the other types - Allows distention of bladder or uterus as it stretches readily A close-up of several cells Description automatically generated Glands - Formed from infolding of epithelial - Exocrine: secrete products through ducts - Endocrine: secrete products into blood (via basal cells)  A diagram of a cell division Description automatically generated  Function of connective tissue: - Support and give strength to tissues and organs - Separates or connects different tissues - Found through entire body - Stores metabolic and kinetic energy - Supplies hormones - Nutritional support - Site of immune reactions Structure of connective tissue: - Extracellular material: proteoglycans, polysaccharides, water and proteins - Fibres: collagen, elastin - Ground substance: glycans, proteoglycans What cells make up the connective tissue: - Fibroblast: biosynthesis of extracellular - Macrophages - Neutrophils - Lymphocytes - Mast cells - Nerve cells - Adipocytes (fat cells) 4 types of connective tissue cell: - Fibroblasts: tendons, ligaments, capsules, bone tissue matrices - Chondroblasts: cartilage - Osteoblasts: bone - Haematopoietic stem cells: blood, WBCs, RBCs Embryonic origin -\> mesenchyme Fibroblasts are formed of dense and loose tissues Types of connective tissue proper: - Dense: higher proportion of elastin Dense (REGULAR): - Tendons: attach muscle to bones - Ligaments: attach bones to bones - A close-up of a purple surface Description automatically generated parallel collagen fibres for high tensile strength Dense (IRREGULAR): - Skin - Organs/joint capsules -  bundles of collagen fibres for high tensile strength Loose (AREOLAR): - Laminar propria/beneath epithelia, around organs - A close-up of a map Description automatically generated collagen fibres to protect organs Loose (RETICULAR): - Lymphoid organs -  reticular fibres and cells to form stroma Loose (ADIPOSE): - Fat - Skin - A close up of cells Description automatically generated adipocytes for insulations, protect organs  A diagram of a bone Description automatically generated  Muscle tissue is comprised of muscle cells which function in a process known as muscle contraction, which is controlled by the nervous system There are 3 different types of muscle: - Cardiac - Smooth - Skeletal Skeletal: - Found all over the body - Approx. 650 different - Attached to bone either directly or via tendons - Produces voluntary movement - Maintains posture - Cells are multi nucleated - Muscle cells known as myoblasts - Myoblasts fuse to form muscle fibre - Nuclei located at periphery of fibre - Each fibre is surrounded by connective tissue (endomysium) - Fibres contain myofibrils\>which contain myofilaments, actin and myosin make these contract - A diagram of the muscles of the arm Description automatically generated Muscle cell contraction: - Requires innervation from the CNS via the peripheral nervous system - Voluntary or somatic nervous system - Innervates at neuromuscular junctions Cardiac muscle: - Striated - Cardiac muscle cells known as cardiomyocytes - Comprised of myofibrils characterised by sarcomeres - Short, branched cells which can communicate with other cells -  Smooth muscle: - Found in most organs - Not striated, no myofibrils - Controls bodily functions eg. Regulates blood pressure, airflow, helps peristalsis, controls urination and controls contraction during birth - A diagram of a structure Description automatically generated - Myofilaments scattered through sarcoplasm - CNS: Brain, spinal cord - Peripheral nervous system: Motor neurons + sensory neurons \< somatic, autonomic\< sympathetic, parasympathetic - Relay information from periphery, via peripheral nerve to CNS (afferent transmission) Interneurons: - Relay information intermediary between sensory and motor neurons Motor neurones - Relay information from CNS back to peripheral nervous system effectors (efferent transmission)  A white background with black text Description automatically generated Myelination provides electrical insulation of axons in axons with no myelination, less saltatory conduction Moodle recap quiz Q: The - of connective tissue is made up of - in which is found -  to provide strength and/or elasticity A: extracellular matrix, ground substance, fibres Q: Give some examples of true epithelia A: Sweat glands of the skin, adrenal gland, lining of the oesophagus, sheet of cells lining the blood vessels Describe these epithelial types Q: Simple cuboidal A: Single layer of cuboidal cells, large spherical nuclei Q: Simple columnar A: Single layer of tall cells, which may have cilia Q: Stratified cuboidal A: Two layers of cuboidal cells, simple squamous Q: Simple squamous A: single layer of flat cells, sparse cytoplasm Q: Pseudostratified columnar A: Single layer of cells with different heights, combined with nuclei at different levels Q: Stratified squamous A: Several layers of cells, thick membrane What type of connective tissue do these cells give rise to? Q: Chondroblasts A: Cartilage Q: Haematopoietic stem cells A: Blood Q: Osteoblast A: Bone Q: Fibroblasts A: Connective tissue proper