Lecture 12: Connective Tissue and Adipose Tissue Flashcards
Functions of connective tissue (x6)
Binding and supporting (eg holding gut, skin, lungs etc together)
Protecting (eg bone protecting vital organs)
Storing reserve fuel and cells (BM and adipose tissue)
Insulation (fat underlying skin and BM holding warm blood)
Transport of substances within body (blood and interstitium)
Separation of tissues (fascia and tendons/cartilage)
Types of connective tissue (x7)
Loose Dense Bone Cartilage Blood Adipocytes Fibrous
Main cells in connective tissue
Fibroblasts Chondrocytes OB/OC/osteocytes Stem cells/progenitor cells/bone barrow/blood Adipocytes
Main products (x3)
Fibres (many types)
Ground substance
Wax and gel-like materials
Loose vs dense connective tissue
Loose:
Areolar tissue; ‘little space’; lamina propria beneath mucosal membranes; around basal lamina; least specialised connective tissue in adults
Dense:
Fibrous or collagenous tissue; two types 1) Irregular (fibres run in different directions) and 2) regular (fibres run parallel to each other)
Loose CT structure
Contains multiple cell types (fibroblast, macrophages, other white blood cells, mast cells, adipocytes)
Two main fibres: collagen and elastic
Gel-like ground substance (proteoglycans, hyaluronic acid etc)
widely distributed under epithelial cell layers eg lamina propria and around glands, surrounds capillaries nerves and sinusoids
Functions of loose connective tissue (x6)
Holds vessels that supply fluids Permits cell migration Involved in inflammatory pathways Acts as packaging around organs Holds everything in place Cushions and stabilises organs
Fibroblasts
Synthesise and secrete fibres that lie in ground substance (ECM)
Important in wound healing - primary cells responsible for producing scar tissue
Myofibroblasts: modified fibroblasts that contain actin and myosin which are responsible for wound contraction when tissue loss has ocured
Macrophage
Derived from blood monocytes and move into loose CT especially during local inflammation
Phagocytes, degrade foreign organisms and debris
Professional APC
Mast cells
Look like basophils but are not derived from them
Cytoplasms abundant granules:
histamine (increase BV permeability); heparin (anti coagulant); cytokines (chemokines that attract eosinophils and neutrophils)
Found in loose CT near blood vessels but ABSENT FROM CNS (avoid damaging effects of oedema)
Mast cells covered in IgE and when allergen cross-links with this, mast cells degranulate.
Adipocytes (unilocular)
Most adipocytes in loose CT white->yellow: white adipocytes
Single, large lipid droplet with nucleus, cytoplasm and organelles localised at the periphery
Has normal number of mitochondria
In adults, lipid breakdown is slow and heat only generated after shivering reflex
Function: padding, shock absorber, insulation, energy reserve
Adipocytes (multilocular)
Brown adipocytes; very few in adult and abundant in babies
In neonates and young children, lipid breakdown is accelerated; OXPHOS is uncoupled to generate heat (calories generated can double)
Multiple small lipid droplets, with nucleus, cytoplasm and organelles centrally localised in cell
Has increased number of mitochondria
Function: insulation and energy reserve
Collagen
CT fibre
Commonest protein in body between 1/3 and 1/4 of our whole body protein content; with ground substance, it constitutes the ECM
Type I: most widely distributed (90% of all collagen) fibrils aggregate into fibrils and fibre bundles (eg in tendons, capsules of organs and skin dermis)
Type II: fibrils don’t form fibres (hyaline, elastic cartilage)
Type III: fibrils form fibres around muscle and nerve cells and within lymphatic tissues and lymphatic organs (eg spleen) and in tendons; called RETICULIN
TYPE IV: unique; found in basement membrane (considered of epithelial tissues)
Examples of loose CT
Submucosa of colon
Superficial layer of dermis
Location of loose CT
Located beneath epithelia (facilitate diffusion)
Associated with epithelium of glands
Located around small BV
