Diversity of Cells and their Function Flashcards
Histological technique steps?
Tissue “fixed” using chemical that cross links proteins, like formalin - preserve in life-like state
Tissue thinly sliced to allow light to penetrate tissue (difficult so tissue IMPREGNATED with support material - like WAX)
To impregnate, tissue dehydrated, put in organic solvent (xylene) and placed in hot was until it fully penetrates tissue
Thin section cut on microtome and put onto microscope slides
Wax washed out, tissue rehydrated
Tissue stained, with coloured dye (differentially bind to particular molecules
How does the histological technique change the original tissue? What is this called?
Produces distortions/changes from original tissue, called ARTIFACTS, like shrinkage
What are the most common combination of coloured dyes used? Limitations
H&E (may not show basal lamina):
Haematoxylin - basic dye with affinity for acidic molecules, nucleus with acidic DNA or ribosomes staining them PURPLISH-BLUE
Eosin - acidic dye with affinity for basic molecules, most proteins in cytoplasm, staining them PINKISH-RED
Basic tissue types?
Epithelia
Connective
Nerve
Muscle
Describe ethelial structure and function?
Cover surfaces/line hollow body organs and form glands, lining of gut/blood vessels
Composed of packed cells and occur as sheets of cells
Common features of epithelia?
ADHESION between epithelial cells is strong, forming sheets of cells and minimising intercellular spaces - allows them to be able to cover surfaces and line cavities
At basal surfaces, sit on basal lamina (basement membrane) to which cells are attached;cells are all NON-VASCULAR as basal lamina separates epithelial cells from blood vessels - nutrients must diffuse across basal lamina
Cells are usually POLARISED as apical and basal ends differ
Pathological significance of basal lamina?
Cells are considered cancerous if they breach the basal lamina
Function of epithelia?
Mechanical barrier - skin Chemical barrier - lining of stomach Absorption - lining of intestine Secretion - salivary gland Containment - lining of urinary bladder Locomotion - oviduct (by cilia)
Shapes of epithelial cells?
Squamous - flat, like fish scales
Cuboidal - cube-shaped
Columnar - like a column, relatively tall and thin
Number of layers of epithelial cells?
Simple - one layer
Stratified - two layers
Pseudostratified - tissues appears to have multiple layers but all cells are actually in contact with basal lamina
Different cell surfaces/tissue surfaces of epithelial tissues?
Prominent microvilli (called “brush border”)
Cilia
Presence of layers of keratin protein on tissue surface (called KERATINISED)
What are goblet cells?
Single-celled mucous glands
What are glandular epithelia? Examples?
Produce secretory products, like sweat, milk, oil, hormones, mucous, enzymes
Endocrine glands (DUCTLESS glands)- products secreted to basal end of cell and distributed to rest of body via vascular system
Exocrine glands (DUCTED glands) - products secreted to apical end of cell into either lumen of an internal space, into duct, or onto body surface
Types of connective tissue? Structure of cells?
Soft connective tissue -tendons, ligaments, mesentary, stroma of organs, skin dermis
Hard connective tissue - bone and cartilage
Blood & lymph - specialised form of connective tissue
Connective tissue consists of cells (minority) and EC matrix (majority). Type of connective tissue is determined by amounts of these 2 components
What types of cells make up connective tissue?
Fibroblasts - widely distributed and produce and maintain the EC matrix
Adipose - fat cells found scattered in many tissues and are predominant in adipose tissue
Osteocytes - bone cells
Chondrocytes - cartilage cells
What does the EC matrix of connective tissue consist of?
Fibres - collagen, reticular, elastic fibres
Ground substance - amorphous space occupying material made of unbranced polysaccharide molecules, called glycosaminoglycans (GAGs) - most are bound to protein cores to form glycoproteins
Tissue fluid
Two types of soft connective tissue? Structures?
Loose - fibres loosely packed and separated by ground substance. Plentiful cells
Dense- collagen fibren densely packed:
Dense regular CT if fibres are aligned, in a tendon
Dense irregular CT if fibres bundles run in many directions, like skin dermis
2 types of hard connective tissue?
Bone
Cartilage
What is bone?
Living tissue penetrated by small canals for blood vessels and nerves, and undergoes re-modelling throughout life
Contains living cells called osteocytes
Bone structure?
Outer shell of dense cortical bone makes up shaft (diaphysis) and cancellous/trabecular bone occupies ends of bone (epiphyses)
What is cartilage?
Strong, flexible, compressible, semi-rigid
Semi-rigid nature of matrix comes from hydrated nature of ground substance (GAGs & proteoglycans)
Cartilage is avascular and receives nutrients from adjacent tissues by diffusion through its matrix
3 types of cartilage?
Defined by EC matrix:
Hyaline (most common) - found at articular surfaces, tracheal rings, costal cartilage, epiphyseal growth plates
Elastic
Fibrocartilage
Structure of muscle cells and function?
Cytoplasms packed with contractile fibres
Cells highly specialised for production of contractile force
Force produced by movement of actin fibres over myosin fibres
Major types of muscle tissue?
Smooth
Skeletal
Cardiac
Nervous
What is smooth muscle?
Involuntary (not under conscious control), visceral (mainly found in organs) and non-striated
Structure of skeletal muscle?
Voluntary and striated (some skeletal muscles are not always under conscious control)
Skeletal muscle fibre is a giant, MULTINUCLEATED, cylindrical cell; fibres may have considerable length
Nuclei are elongated and at cell periphery, just internal to cell membrance - called SARCOLEMMA in muscle cells
Structure of cardiac muscle? Locations?
Striated, but less prominent and fibres much shorter than skeletal muscle and branch to form complex network
Single nucleus located near centre of fibre
Intercalated discs seen passing across fibres at irregular intervals - sites of end to end attachment between adjacent cells and contain multiple intercellular junctions to maintain mechanical integrity
Forms major part of heart chamber walls and origins of great vessels
Structure of nervous tissue?
Consists of neurons and GANGLIA (support cells that outnumber neurons 10:1 in CNS)
Nervous system surrounded by connective tissue “coat”:
Meninges in CNS
Epineurium in PNS
3 main types of neuron?
Bipolar neurons
Unipolar neurons
Multipolar neurons
