Connective Tissue Histology PDF

Connective Tissue ANAT2241: Histology JOYCE EL-HADDAD [email protected] @orientatewithjoyce Lecture Outline Learning Outcomes: LO1. To understand the structure and function of the cell types found in connective tissues - Function of connective tissue - Components of CT: cells and extrace...

Connective Tissue ANAT2241: Histology JOYCE EL-HADDAD [email protected] @orientatewithjoyce Lecture Outline Learning Outcomes: LO1. To understand the structure and function of the cell types found in connective tissues - Function of connective tissue - Components of CT: cells and extracellular matrix - Classification of CT - Cartilage - Bone Textbook reference: Netter’s Essential Histology LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue LO3. To recognise adipose tissue (white and brown fat) and understand its functions. Function of Connective Tissue • Provides structural and metabolic support to other tissues; protection, transport, repair, storage. • With few exceptions well vascularised. • Consists of: • Cells • Extracellular matrix (major constituent) o Fibers o Ground substance LO1. To understand the structure and function of the cell types found in connective tissues Main Components of Connective Tissue - Cells - Extracellular matrix (ECM) LO1. To understand the structure and function of the cell types found in connective tissues Connective tissue cells • Develop from embryonic mesenchymal cells. • “Blast” (immature) – “cyte” (mature). • Two types of cell groups: 1. Resident (fixed) 2. Wondering (transient) (migrated from blood as a result of specific stimuli). LO1. To understand the structure and function of the cell types found in connective tissues Connective tissue cells • Fixed: – Fibroblasts – Adipocytes – Chondroblasts – Osteoblasts • Wondering (fixed) (histiocytes): – Mast cells – Macrophages – Lymphocytes – Plasma cells – Eosinophils LO1. To understand the structure and function of the cell types found in connective tissues Mesenchymal Cells • Primitive stem cells • Differentiate into connective tissue, bone, blood, lymph, endothelium, and muscle cells • Some mesenchymal cells maintain their plasticity throughout adult life • Histologically resemble fibroblasts, but are generally smaller • Clinical context: sarcomas (tumors of connective tissue) Umbilical cord banking LO1. To understand the structure and function of the cell types found in connective tissues Fibroblasts • Fibroblasts = basophilic = more organelles and protein synthesis [blue] • Fibrocytes = acidophilic – cytoplasm [pink] • Synthesize collagen, elastic and reticular fibers and other extracellular • material. • Fibroblasts are active in the repair of injury and formation of scar tissue. Connective Tissue Nucleus Rough endoplasmic reticulum Fibroblast transformation Cytoplasm Golgi complex Undifferentiated mesenchymal cell (Inactive) LO1. To understand the structure types found in connective tissues 55 Tropocollagen Mature, collagen-producing fibroblast (Active) Undifferentiated mesenchymal cells. They can transform into active fibroblasts by developing organelles essential for collagen synthesis and secretion. This occurs during early development and is a hallmark of wound healing, when cell transformation and production of collagen accompany migration and function ofto the and proliferation of cells wound cell sites. Undifferentiated mesenchymal cells. They can transform into active fibroblasts by developing organelles essential for collagen synthesis and secretion. This occurs during early development and is a hallmark of wound healing, when cell transformation and production of collagen accompany migration and proliferation of cells to wound sites. • Fibroblast nucleus = eurochromatic, with some heterochormaticy shown around the periphery of the nucleus (towards the nuclear envelope) Collagen Fi Fi Fi Fi TERMINOLOGY CHECK: - Eurochromatic: loosely packed chromatin. DNA accessible for transcription (stains lightly) - Heterochromatic: tightly packed chromatin. DNA inaccessible for transcription (dark appearance) 1µm EM of a growing tendon during the adolescent growth spurt. Nucleated regions of several active fibroblasts (Fi) are evident. Euchromatin predominates in the nuclei. The cytoplasm contains many closely packed organelles. Many branching processes (arrows) emanate from the cell bodies. Collagen fibrils occupy the intervening ECM and are sectioned transversely. Cell-to-cell contacts between fibroblasts are circled. 9000×. 3.4 STRUCTURE AND FUNCTION OF FIBROBLASTS Fibroblasts, the main cell type of connective tissue, are the most common cell of loose (areolar) connective tissue and virtually the only cell of dense regular connective tissue such as tendon. They function in synthesis and secretion of ground substance and, as their name implies, of connective tissue fibers, including collagen and elastic or reticular fibers, in the ECM. In mature connective tissue, these cells are relatively inactive and immobile and are ECM fibers and ground substance. Fibroblasts are ovoid or stellate cells with long, tapering processes that branch. They have one elliptical nucleus, usually euchromatic, with one or more distinct nucleoli. Light microscopy shows that staining attributes of their cytoplasm differ according to functional state. Active or immature cells have a weakly basophilic, relatively conspicuous cytoplasm. Mature cells have a weakly acidophilic, barely visible cytoplasm with a relatively homogeneous appearance, so that nuclei are seen mainly in histologic sections. Routine preparations Adipocytes • Two types of adipocytes: brown and white • White adipocytes: o Specialised for fat storage, energy and insulation; involved in the synthesis of hormones and growth factors. • o Located throughout loose connective tissue. o Cytoplasm with flattened nucleus forms a very narrow rim around a large central lipid droplet. o Unilocular Brown adipocytes: o Brown appearance and rich in mitochondria o In adult life, brown fat persists in back, neck, and thigh o Function: heat generation and non shivering thermogenesis o Multilocular LO1. To understand the structure and function of the cell types found in connective tissues Macrophage – Pacman of the cell • Develop from monocytes (WBC). • Irregular shape, short branched projections. • Destroys bacteria and cellular debris (phagocytosis). • Fixed and wondering. 66 Connective Tissue * Ly Nucleus of macrophage Mi * EM of a macrophage. The cell is sectioned at the level of its nucleus, which has an irregular outline, slightly eccentric location, and finely dispersed chromatin. The cytoplasm contains many vesicles, mitochondria (Mi), and other closely packed organelles. Numerous lysosomes at various developmental stages are scattered throughout the cytoplasm and range from small primary (Ly) to large tertiary (*) lysosomes. The cell surface bears many cytoplasmic processes, or pseudopods (arrows). 11,000×. Ly 2 µm Co EM of parts of two macrophages. Primary lysosomesof (Ly),the close to cell the nucleus, have a dense, LO1. To understand the structure and function education.vetmed.vt.edu/Curriculum/VM8054/Lab... homogeneous electron-dense core. The larger tertiary lysosomes (*), more irregular in shape, contain a types found in connective tissues Ve * Mast cells • Develop in bone marrow, differentiate in connective tissue. • Function: inflammatory and allergic response (granules contain histamine, heparin), kill bacteria. 62 Connective Tissue LM of a mast cell in connective tissue. It has many granules in its cytoplasm and is close to a venule, which is filled with erythrocytes. 800×. H&E. Mast cell Venule Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. EM of a mast cell in connective tissue. This section is at the level of the cell nucleus, which is euchromatic with peripheral patches of heterochromatin and a prominent nucleolus (*) at its center. An irregular cell border with filopodia (arrows) is a distinctive feature of the cell surface. Many prominent, moderately electron dense granules (Gr) fill the cytoplasm. Collagen fiber bundles (Co) are in the extracellular matrix. 11,000×. LO1. To understand the structure and function of the cell types found in connective tissues Co EM of a mast cell in loose connective tissue. The cytoplasm shows the granules (Gr) that vary in size, shape, and electron density. Short, stubby filopodia (arrows) project from the cell surface. Collagen fibrils (Co) occupy extracellular matrix. 10,000×. Co Extracellular matrix • Fibres – Collagen, reticular, elastic. • What cell produces the fibres? Ground substance – Fluid, semisolid, solid. – Consists of water and complex carbohydrates and glycoproteins - make up a flexible gel. • Functions: mechanical and structural support for tissue; biochemical barrier-role in regulating metabolic functions in surrounding cells. LO1. To understand the structure and function of the cell types found in connective tissues Fibers TYPE FUNCTION Collagen • • Reticular • • Elastic • Most abundant type; closely packed and orderly, flexible, high tensile strength. Made of collagen protein. Very thin, type IIl collagen associated with high levels glycoprotein; Provides a supporting framework for the cellular constituents of various tissues and organs – (reticular tissue) stroma. Thin, elastic (protein elastin), allows tissue to respond to stretch and distensions; located in skin, lung and bladder. LO1. To understand the structure and function of the cell types found in connective tissues Collagen BASIC Scurvy disease http://medcell.med.yale.edu/histology/connective_tissue_lab/collagen_fibers_em.php Skin care routine! Elastic Fibers Marfan Syndrome Think hair on tiles Reticular fibers https://bcrc.bio.umass.edu/courses/spring2018/biol/biol523/content/reticular-connective-tissue20x-1 https://www.google.com/url?sa=i&url=http%3A%2F%2Flecannabiculteur.free.fr%2FSITES%2FUNIV%2520W.AUSTRALIA%2Fmb140%2FCorePages%2FConnec tive%2FConnect.htm&psig=AOvVaw3QfJsxriGBYNgCY3GJOud&ust=1654311308864000&source=images&cd=vfe&ved=0CAwQjRxqFwoTCMi2g4OkkPgCFQAAAAAdAAAAABAD CLASSIFICATION OF CT LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Dense connective tissue LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Dense regular connective tissue • Abundant collagen fibers, few cells and little ground substance. • Uniformly aligned densely packed fibers collagen arranged in bundles – fibroblasts arranged in rows between collagen bundles. • Location: tendons and ligaments. • Function: reinforces attachment between organs LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. Dense irregular connective tissue • Mostly collagen fibers, few cells and little ground substance. • Tightly packed fibers random in 3 dimensions. • Location – fasciae, the dermis (reticular or deep layer) and digestive tract (submucosa). • Function - strength, resists stretch/tearing in multiple directions. LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. Elastic connective tissue • Predominantly elastic fibers; fibroblast in the spaces btw the fibers. • Yellowish in colour; stretching capability; lungs, elastic arteries, some ligaments. LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Loose connective tissue Loose Areolar tissue • Most common type; all three types of fibres, abundant ground substance, several diff. cells; delicate consistency, flexible, and well vascularised. • While it allows for movement between adjacent structures, it inhibits distorsion. • Subcutaneous layer, surrounds lymph and blood vessels, nerves and body organs, lamina propria of mucous membranes, dermis of skin (superficial layer). LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Loose - Reticular connective tissue • Intertwining reticular fibers. • Forms the stroma, binds smooth muscle cells; reticular fibers filter blood and lymph. LO2. To understand the structure and function of reticular, areolar (loose) connective tissue and dense connective tissue Adipose tissue • Two types of adipocytes: brown and white • White adipocytes: o Specialised for fat storage, energy and insulation; involved in the synthesis of hormones and growth factors. o Cytoplasm with flattened nucleus forms a very narrow rim around a large central lipid droplet. o Unilocular o Location subcutaneous, around organs e.g. heart, kidney Brown adipocytes: o Brown appearance and rich in mitochondria o In adult life, brown fat persists in back, neck, and thigh o Function: heat generation and non shivering thermogenesis o Multilocular LO3. To recognise adipose tissue (white and brown fat) and understand its functions. WELCOME TO [email protected] @orientatewithjoyce Contact Information Course Convenor: Joyce El-Haddad • Email: [email protected] • Consultation hour: by appointment only Course Co Convenor: Dr Reza Shirazi • Email: [email protected] • Consultation hour: by appointment only 2 Email etiquette [from your UNSW email ONLY] • An example of what to do: ‘ Hi Joyce, My name is Lilly, and I am from ANAT2241 I was wondering if…..” Thank you, Lilly’ • An example of what NOT to do: ‘ can u check my grade From • [email protected]’ What do I do if I feel overwhelmed with the course? • We are here for you. • Contact the course convenors at any point in the term if you are feeling overwhelmed. • We can help you and work through solutions and/or point you to the right direction for help. Moodle and Teams tour Cells and Epithelium JOYCE EL-HADDAD [email protected] @orientatewithjoyce Lecture Outline • Cellular structure overview • Basic tissues • Structure of epithelium • Classification of epithelium • Structure of connective tissue • Classification of connective tissue Structural organisation of the body - 6 levels Tortora, 11th Edition 8 Cellular structure overview Cell biology Human body: 60-100 trillion cells; ~ 200 different types, variety of shapes and sizes (red blood cell 7.5, ovum 140 µm in diameter). Structure → Function 1 µm = 0.001 mm 1 nm = 0.001 µm Cellular structure Main components: plasma membrane, nucleus and cytoplasm. Human egg (oocyte) Plasma membrane Cytoplasm Nucleus http://www.advancedfertility.com/egg2.htm Plasma Membrane Plasma Membrane • Dynamic interface between the internal environment of the cell and its various external environments. • Functions as a physical barrier; regulates movement of molecules into and out of the cell; mediates cellular recognition and interaction. • Its interaction depends on the specialised function of the cell – selective permeability. • Membranes of organelles have the same basic structure. • Made of lipids and proteins - bilayer phospholipid. • Proteins: receptors, enzymes, cell identity markers. OUTSIDE THE CELL Hydrophobic tail of phospholipid (no affinity for water) Hydrophilic head of phospholipid (affinity for water) INSIDE THE CELL OUTSIDE THE CELL EXTR I PRO NSIC TEIN S Hydrophobic tail (no affinity for water) EXTR I PRO NSIC TEIN S INSIDE THE CELL INTEGRAL (intrinsic) PROTEINS Hydrophilic head (affinity for water) OUTSIDE THE CELL Lipid+ carbohydrate group = glycolipid INTEGRAL (intrinsic) PROTEINS Hydrophobic tail (no affinity for water) EXTR I PRO NSIC TEIN S Carbohydrate group Protein + carbohydrate group = glycoprotein INSIDE THE CELL EXTR I PRO NSIC TEIN S Hydrophilic head (affinity for water) http://biopic.xinwen365.com/Cellstructureandfunction.htm http://fig.cox.miami.edu/~cmallery/150/memb/membranes.htm Plasma membrane • Fluids: intracellular (cytosol) and extracellular (interstitial; plasma and lymph) Movement through cell membranes: Passive o Diffusion: tendency of molecules to move from regions of ↑ to ↓concentration; o Facilitated diffusion: diffusion with the aid of membrane carriers; o Osmosis: passive movement of H2O mol. from regions of ↑ to ↓ H2O conc. Active o Active transport: carrier mediated transport of solutes from regions of their ↓ to ↑ concentration (against the concentration gradient) o Endocytosis: 1) Pynocytosis: membrane engulfs small droplets of fluid from extracellular environment, 2) Phagocytosis: membrane engulfs solid particles from extracellular environment; o Exocytosis: Release of molecules from cells as vesicle rupture. PASSIVE Diffusion ACTIVE Endocytosis Exocytosis https://d2gne97vdumgn3.cloudfront.net/api/file/fS9PB7RTRUComBuyBTK5 Nucleus Bounded by a double layered nuclear membrane (envelope); nuclear pores (selective gates: allow passage of material into and out of the nucleus). Contains nucleoproteins and DNA, which encodes the instructions for making cells, tissues, organs, and eventually, the whole organism. Nucleus Chromatin: a coiled threadlike mass, consists of DNA, protein and some RNA; when a cell begins to divide it shortens and thickens into rod-shaped structures – chromosomes (n=46 [23 pairs]). Nucleolus: a spherical structure within the nucleus; produces components of the ribosomes, which are important in protein synthesis. Nucleus Nucleolus Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. http://www.lumen.luc.edu/lumen/MedEd/Histo/frames/h_frame2.html http://www.lbl.gov/ScienceArticles/Archive/assets/images/2002/Nov-152002/uncoiled_chromatin.jpg Cytoplasm = cell fluid • The part of the cell outside the nucleus; bounded by the plasma membrane. • Consists of cytosol and organelles. CYTOSOL Cytosol (fluid portion): water, dissolved solutes, suspended particles (the metabolic products of the cell; specific for particular cell types; non-moving, non-living components of the cell such as pigment granules, lipid droplets, glycogen). Organelles Specialized structure within the cell which regulate cellular growth, maintenance and reproduction. • Cytoskeleton • Rough-surfaced endoplasmic reticulum (rER) • Smooth-surfaced endoplasmic reticulum (sER) • Golgi apparatus • Endosomes • Lysosomes • Transport vesicles • Mitochondria • Peroxisomes • Centrioles • Ribosomes Cytoskeleton = cell framework Function is to maintain structural integrity of cells that are dynamic in nature. It is also necessary for movement of cell organelles, cell locomotion and muscle fibre contraction. Endoplasmic reticulum Endoplasmic reticulum Complex network of interconnected membranes (n. envelope); btw. membranes minute spaces – cisternae. Pathway for transportation of substances and storage area for synthesised molecules. Rough (granular) endoplasmic reticulum: to the presence of ribosomes on the membrane surface; rER is where most protein synthesis occurs; products are enclosed in vesicles for transport. Smooth endoplasmic reticulum: mainly involved in lipid synthesis and detoxification (Lipid soluble drugs into water soluble drugs = expulsion). LONG TERM USE OF DRUGS AND ALCOHOL – PROLIFERATION OF ER! Golgi complex (aparatus) Membranes, cisternae. Completes post-translational modifications, sorting and packaging the products synthesised by the cell; cellular secretion → vesicle (exocytosis). Golgi apparatus Vesicle http://cdn.yourarticlelibrary.com/wp-content/uploads/2014/03/image191.png Roses are red, violets are swell Mitochondria = granular thread • Bounded by double membranes: outer smooth, inner – folds/cristae (surface area for chemical reactions). • “Cell powerhouse”: perform aerobic respiration, converting carbohydrates + oxygen into carbon dioxide + water, thus generating energy (in the form of Adenosine Triphosphate i.e. ATP). • Own DNA, matrilineal inheritance (endosymbiotic origin). Lysosomes Membrane bounded vesicles of various shapes and sizes produced by the Golgi complex. Contain more ~ 60 digestive enzymes which act upon macromolecules from within or outside the cell. CELL (an electron micrograph) Basic tissues A group of similar cells and cell products that perform a special function; cells + extracellular matrix (liquid, semisolid, solid). 4 basic (fundamental) tissues: • Epithelial • Connective • Muscle • Nervous Same, same but different Basic tissues Tissue Cells Extracellular Matrix Main function Epithelial Aggregated, polyhedral cells Small amount Lining of surface or body cavities, glandular secretion Connective Several types of fixed and wondering cells Abundant amount Support and protection Nervous Intertwining elongated processes None Transmission of nervous impulses Muscle Elongated contractile cells Moderate amount Movement EPITHELIAL TISSUE Epithelial tissue • The principal function: covering, lining and protecting surfaces (e.g., skin and gut), secretion (glands), absorption (intestine), sensation (neuroepithelium), contractility (myoepithelial cells). Lamina Propria Two main types (arbitrary division): • Surface: the cells are organised in layers that cover the external surface or line the cavities of the body. • Glandular: the cells specialised to produce secretions. Epithelial tissue • Consists of an uninterrupted layer of tightly packed cells. Holes such as the pores of a gland are an invagination of epithelium. • Polarised: has a free surface (the apical surface) exposed to the outside and the basal surface (opposite) which may be attached to the underlying connective tissue. • One or several layers of cells: apical (free) and basal layers. • Lamina propria is the layer of connective tissue underlying the epithelium – bound to epithelium by the basement membrane. • Basement membrane is formed by secretion of both, epithelial cells and cells in connective tissue. • Basement membrane also functions as a selectively permeable filter between epithelium and connective tissue. • Epithelium is avascular – receives nutrients by diffusion from lamina propria which is essentially connective tissue. 1. To identify and describe the different types of epithelia Specialisations of the cell surface Microvilli: folds of the plasma membrane – increase surface area, therefore, increase absorption Cilia: projections of the plasma membrane. Locomotion. Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. Surface Epithelium Classification of Epithelium Simple squamous epithelium • Flat, irregularly shaped, tightly-fitted cells in a mosaic-like pattern; with flattened centrally located nucleus. • Function: diffusion and filtration. • Location: pulmonary alveoli, kidneys, lining the inner walls of blood and lymphatic vessels (endothelium), form serous membranes that line the body cavities and its organs – pericardium, pleura, peritoneum (mesothelium). Simple cuboidal epithelium • Composed of tightly fitted cube-shaped cells, with centrally positioned round nucleus. • Function: secretion, filtration and absorption. • Location: found in many glands and glandular organs and ducts (surface of the ovaries, ducts of the salivary glands and pancreas), lines the kidney tubules. Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. Simple columnar epithelium • Composed of tall, columnar cells of variable height, tightly fitted, nucleus usually located close to the basement membrane. • Existence of goblet cells. • Can be ciliated or not ciliated. Structure depends on function. • Function: protection, lubrication, secretion and absorption. • Location: lining of intestine, uterine tubes, bronchioles. Simple Columnar Epithelium Pseudostratified epithelium • Cells are of different heights with a variable position of the nucleus, giving the appearance of being stratified; goblet cells. • Non-ciliated or ciliated. • Function: protection, secretion, if ciliated involved in movement of particles. • Location: trachea, bronchi, nasal cavity. Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. http://www.lab.anhb.uwa.edu.au Stratified squamous epithelium • • • • Apical surface cells are squamous while the cells closer to the underlying connective tissue are cuboidal to columnar. Function: found in areas subjected to wear and tear (abrasion); top layer cells are rubbed away and replaced via mitosis of the basal cells. Keratinised (dry) contains keratin, a protein that strengthens the tissue; function: protection, prevents water loss; location epidermis. Nonkeratinised (wet) mucosa; function: protection, secretion; location: mouth, esophagus, larynx, vagina, anal canal. Junqueira LC & Carneiro J, 2003, Basic Histology, 10th ed. http://www.siumed.edu/~dking2/intro/GI006c.htm Cervical Screening Test (CST) @orientatewithjoyce Transitional epithelium • Characterized with cells that change form according to the degree of distension – flat (squamous) when stretched and cuboidal when relaxed. • Function: protection, distensibility. • Location: lining the cavity of urinary bladder, ureters, renal calyces. Glandular Epithelium Endocrine glands Exocrine glands A. B. C. D. E. F. Schematic showing development of glands. A. Epithelium lining and surface. B. Proliferation of epithelium. C. Penetration into underlying connective tissue. D. Formation of lumen, which opens on a free surface, and thus an exocrine gland. E. Some cells separate from surface epithelium to form endocrine glands. Capillaries are in close contact with cords of epithelial cells. F. In some glands (e.g., thyroid), lumina form in follicles but without surface connections. Compound acinar Overview of exocrine glands • EXO = outside • Crine (krinein – Greek) = sift • A gland that makes substances such as sweat, tears, saliva, milk and digestive surfaces and releases them through a duct or opening to a body surface @orientatewithjoyce • Endocrine glands are ductless and release products, called hormones, directly into the bloodstream. • These glands are arranged in cords or clumps of cells, close to a complex network of capillaries, for hormone transport. • Exocrine glands connect to the surface by ducts, which take the secretions to the surface or lumen. The epithelial, or functional, component of all glands is parenchyma; the mainly supportive connective tissue part is stroma.