Principles of Human Structure - Introduction and The Cell PDF 2024-2025

Principles of Human Structure AN1004, AN1005, AN1075, AN2003 Introduction and The Cell Dr Siobhain O’ Mahony  Information Contact details – Department of Anatomy and Neuroscience Western Gateway Building – [email protected] (UCC email address...

Principles of Human Structure AN1004, AN1005, AN1075, AN2003 Introduction and The Cell Dr Siobhain O’ Mahony  Information Contact details – Department of Anatomy and Neuroscience Western Gateway Building – [email protected] (UCC email addresses only) Class reps, please send your contact details Canvas A module hand-out is available with an up-to-date timetable The material is organised by week. Everything needed for each week will be uploaded by the Monday. Material includes: – PowerPoint pdfs – Links to the 20-30 minute video recordings with 3-4 MCQs  Module information Learning outcomes: – Describe the major body systems: cardiovascular, digestive, musculoskeletal, nervous, respiratory, urinary system, reproductive. – Use appropriate anatomical terminology. – Identify important features of organs. – Compare and contrast structural properties of tissues and organs. – Describe the function of organs. – Discuss the structure-function relationship of organs. Module content – Anatomical terminology, Skeletal system, Joints, Muscular system, Cardiovascular system, Respiratory system, Nervous system*, Digestive system, Urinary system, reproductive system. Recommended textbooks – Tortora & Nielsen: Principles of Human Anatomy, Wiley & sons. – Marieb, Mallat & Wilhelm: Human Anatomy, Pearson. – Martini, Timmons, Tallischt: Human Anatomy, Pearson.  Timetable Lecture Date Topic Venue Number 1 26 Sept Welcome Introduction and The Cell Boole 3 2 27 Sept Anatomical terminology Boole 4 3 3 Oct Skeletal system 1 Boole 3 4 4 Oct Skeletal system 2 Boole 4 5 10 Oct Joints 1 Boole 3 6 11 Oct Joints 2 Boole 4 7 17 Oct Muscle tissue 1 Boole 3 8 18 Oct Muscle tissue 2 Boole 4 9 24 Oct Cardiovascular system 1 Boole 3 10 25 Oct Cardiovascular system 2 Boole 4 11 31 Oct Respiratory system Boole 3 12 1 Nov Urinary system Boole 4 13 7 Nov Nervous system 1 Boole 4 14 8 Nov Nervous system 2 Boole 3 15 14 Nov Digestive system 1 Boole 3 16 15 Nov Digestive system 2 Boole 4 17 21 Nov Reproductive system 1 Boole 3 18 22 Nov Reproductive system 2 Boole 4  Assessment It is the student’s responsibility to ascertain the dates on which the examination will be held. Course work is examined by continuous assessment only in the form of online assignments (5 x 20% each). A series of 40 questions will be made available to you on Canvas on each of the dates specified on the next slide. The time of each exam is set from 2pm to 2:30pm unless otherwise indicated. You will be allowed to complete the assessment in one sitting i.e. once you start the assessment, you will not be able to log in at a later time to complete it during that week. Only one attempt is allowed at each assessment. Questions will be in MCQ or fill-in-the- blanks-format and will be based on the material covered in lectures in the previous weeks. A detailed set of instructions outlining how to log-in and complete the assessment will be made available to you in advance of the assessment dates. The pass mark is 40%. Students who fail assessments will be required to repeat the examination in the Autumn examination period. AN2003-Final mark counts towards your choice of outlet for 3rd and 4th year BSc  Assessment Assess- number Topic Date 1 The cell, anatomical terminology and skeletal system (1 and 2) Friday 13th Oct 2 Joint (1 and 2) and muscle tissue (1 and 2) Friday 1st Nov 3 Cardiovascular system (1 and 2) and Respiratory system Friday 15th Nov 4 Urinary system and nervous system (1 and 2) Friday 29th Nov 5 Digestive system (1 and 2) and Reproductive system (1 and 2) Friday 13th Dec The Cell Histology Histology-also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues Histology is the microscopic counterpart to gross anatomy, which looks at larger structures visible without a microscope. Histology is performed by examining thin slices (sections) of tissue under a microscope. Light microscope: large areas (several cm2) wide range of stains up to ~ 1000 X mag. Electron microscope: small areas (< 1mm2) subcellular resolution up to ~ 100,000 X mag. Electron Microscope An electron micrograph is a micrograph prepared using an electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination Electron micrograph (EM) of a cell, X 15,000 Stains can be used to identify specific structures or molecules in the cell / tissue STAIN COLOUR SPECIFICALLY STAINS Haematoxylin purple/blue nucleus nucleic acids Eosin red/pink cytoplasm elastic and reticular fibres Toluidine blue blue nucleus and general cell stain cytoplasm Silver black / brown nerve and reticular fibres Periodic acid- purple/blue carbohydrates Schiff (PAS) Alcian blue blue extracellular acidic epithelial mucins matrix of support cells Cyanin purple myelin myelin  Haemotoxylin & Eosin stain Most commonly used staining system is called H&E (Haemotoxylin and Eosin) Eosin is an acidic dye It stains structures red or pink. Thus the cytoplasm is stained pink in the picture Haematoxylin can be considered as a basic dye. It is used to stain structures a purplish blue Thus the nucleus is stained purple This means that the nucleus, and parts of the cytoplasm that contain RNA stain up in one colour (purple) The rest of the cytoplasm stains up a different colour (pink) Light micrograph (LM) of cells, X 480 Definitions Morphology : study of the form and shape of structures Morphometry: measurement of the shape of structures Stereology: examination of 2D images to gain information about 3D structures The cell Cells are the building blocks of all animals and plants All cells come from the division of pre-existing cells Cells are the smallest units that perform all vital physiological functions Each cell maintains homeostasis at the cellular level Cytology: the study of cellular structure and function Main constituents of a cell and their distribution  Types of cells There are over 200 different cell types in the human body Each type of cells is specialised to carry out a particular function, either solely, but usually by forming a particular tissue Different tissues then combine and form specific organs, where the organ is like a factory where every type of cell has its own job Since every tissue has its own function that contributes to the multifunctionality of an organ, every type of cell is equally important Two major divisions Sex cells/gametes are cells that fuse during sexual reproduction Sperm, oocytes Somatic cells All other cells in the human body Any biological cell forming the body of an organism; that is, in a multicellular organism any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell In mammals somatic cells make up all the internal organs, skin, bones, blood and connective tissue Approximately 220 types of somatic cell in the human body. Cell membrane Separates the cell contents (cytoplasm) from the extracellular fluid (interstitial fluid) cytoplasm = cytosol + organelles Functions: Physical isolation Regulation of exchange with the environment Sensitivity to the environment Structural support  Structure of the Cell Membrane Membrane is formed by a lipid bilayer, with specialised proteins and surface carbohydrates Each lipid molecule is amphipathic - hydrophilic end (phosphate) - hydrophobic end (lipid) Forms a bilayer in water Membrane phospholipid molecule: Main component of cell membranes and determines the fundamental properties of the cell membrane as a whole. The cell membrane is composed of a lipid bilayer with phospholipid hydrophobic groups facing inward and hydrophilic groups facing outward. Protein molecules float within this basic structure, with projecting carbohydrate groups being attached to glycolipids or proteins.  Membrane lipids Three types of lipid Phosphoglycerides (phospholipids) - ~50% of membrane lipid - surround and anchor proteins - phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine Cholesterol - stabilises membrane Glycolipids - intercellular communication - eg. sphingolipids, gangliosides Membrane lipids Cholesterol-stabilises the membrane Glycolipids-intercellular communication Phospholipids-surround and anchor proteins Membrane proteins Functions: Attach cytoskeletal filaments to cell membrane Attach cells to extracellular matrix Transport molecules into and out of cells Act as receptors for chemical signalling between cells Possess specific enzymatic activity Membrane proteins An integral membrane protein (IMP)-permanently attached to the biological membrane IMPs comprise a significant fraction of the proteins encoded in an organism's genome. Peripheral membrane proteins- proteins that adhere only temporarily to the biological membrane. Attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer Regulatory protein subunits of many ion channels and transmembrane receptorsmay be defined as peripheral membrane proteins Membrane carbohydrates Mainly on extracellular surface, as a coating called the glycocalyx Functions: Lubrication and protection Anchoring and locomotion Specificity in binding Recognition Transport across cell membranes Diffusion (gases, lipophilic or small molecules) Active transport (Na2+ ions) Bulk transport - endocytosis - pinocytosis - phagocytosis - exocytosis Endocytosis Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material.  Pinocytosis Pinocytosis, otherwise known as fluid endocytosis and bulk-phase pinocytosis, is a mode of endocytosis in which small particles suspended in extracellular fluid are brought into the cell through an invagination of the cell membrane, resulting in a suspension of the particles within a small vesicle inside the cell. These pinocytotic vesicles subsequently fuse with endosomes to hydrolyze (break down) the particles. Phagocytosis Phagocytosis is the process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome. It is one type of endocytosis. In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris Exocytosis Exocytosis is a form of active transport and bulk transport in which a cell transports molecules out of the cell by secreting them through an energy-dependent process The Nucleus Bounded by nuclear envelope Communicates with cytoplasm through nuclear pores Contains - cellular DNA - nucleoli (rRNA, mRNA, tRNA) - nucleoproteins Chromatin is a complex of DNA and protein found in eukaryotic cells. Its primary function is packaging long DNA molecules into more compact, denser structures: DNA wraps around histone proteins, forming nucleosomes and the so-called "beads on a string" structure (euchromatin). Multiple histones wrap into a 30-nanometer fibre consisting of nucleosome arrays in their most compact form (heterochromatin) Electron micrograph showing typical cell nucleus. The nucleus (N) is clearly visible as an electrode-dense circular area. Nucleus chromatin is divided into two types: heterochromatin (H) is dense-staining, whereas euchromatin (E) is light-staining DNA is organised around histones into nucleosomes. The nucleosomes are wound into a helix to form chromatin. In chromosomes this is then wound again into a supercoiled structure. Important nuclear structures This cell was frozen and then broken apart to make its internal structures visible. The technique, called freeze fracture or freeze etching, provides a unique perspective on the internal organisation of cells. The nuclear envelope and nuclear pores are visible. The fracturing process broke away part of the outer membrane of the nuclear envelope, and the cut edge of the nucleus can be seen. Nuclear pore ▪ Double nuclear membrane (NM) is perforated by nuclear pores (P) –appear as gaps ▪ Pores are formed by concentric rings of subunits to form the nuclear pore complex. ▪ Above and below the large protein units are rings from which filaments radiate into nuclear and cytoplasmic spaces ▪ The structure formed by rings and filaments in the nuclear space-nuclear basket ▪ Pores form channels for transport of small molecules, but restrict large molecules between cytosol and nucleus Endoplasmic Reticulum Network of membranous tubules, vesicles and cisternae Two types: rough ER (surface is studded with ribosomes) function - protein synthesis smooth ER functions - lipid synthesis, membrane synthesis and repair Golgi Apparatus Membrane system involved in sorting, packaging and transporting cell products - modification of macromolecules by addition of sugars - proteolysis of peptides into active forms - sorting of macromolecules into membrane- bound vesicles -transport of lipids around the cell, and the creation of lysosomes -sacs or folds of the Golgi apparatus are called cisternae. Lysosomes Membrane-bound spherical organelle containing hydrolytic enzymes -break down many kinds of biomolecules engulfed by cell A lysosome has a specific composition, of its membrane proteins, and luminal proteins Lumen's pH (~4.5–5.0)-optimal for the enzymes involved in hydrolysis, analogous to the activity of the stomach Involved in various cell processes-plasma membrane repair, cell signalling, and energy metabolism Mitochondria Membrane-bound organelle - outer and inner membranes, separated by intermembranous space Responsible for energy (ATP) production Matrix contains many enzymes and small amounts of mitochondrial DNA Electron micrograph of a mitochondrion. Outer membrane (OM), inner membrane and cristae (C) Cytoskeleton In eukaryotes the cytoskeleton is composed of three main components-all capable of rapid growth or disassembly dependent on the cell's requirements. Microfilaments-long, thin filaments of actin (5nm diameter) Functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape Intermediate filaments desmin, glial fibrillary acidic protein, (a) Cytoskeleton provides keratin, lamin,neurofilaments, strength and structural vimentin (10nm diameter) support for the cell and its Most stable component of the cytoskeleton-found in organelles. Interactions particularly durable structures such as hair, scales, between cytoskeletal fingernails. components are important in Microtubules  and  tubulin moving organelles and in (25nm diameter) changing the shape of the Provide platforms for intracellular transport and are cell. involved in a variety of cellular processes, including the movement of secretory vesicles, organelles (b) Microfilaments and microvilli of an intestinal cell. Scanning electron microscope (SEM) image An interesting website: Biovisions at Harvard University http://multimedia.mcb.harvard.edu/ ‘Inner Life of the Cell’ Look out for - cell membrane (eg. lipid bilayer, sphingolipids, membrane proteins, cholesterol) - protein production and trafficking (eg. ribosomes, Golgi apparatus, mitochondria) - cytoskeleton (eg., actin filamentss) Diagrams used in this lecture were taken from: Wheater’s ”Functional Histology” (4th ed.) Kierszenbaum “Histology and Cell Biology” Martini “ Anatomy and Physiology” (7th ed.) Stevens & Lowe “ Human Histology” (3rd ed.)