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The Cell The Cell RevisedRevised
The Cell Revised Histology
The study of the structure and form of cells and tissues
What is a cell? Bases of all life Smallest unit of matter that can live independently
and reproduce itself Exist in all shapes and sizes
Elongated Square Star-shaped Oval
The Cell Revised What is a cell composed of?
What is a cell look like?
Protoplasm Made up of 70% water and Compounds of
Organic and inorganic saltsCarbohydrates LipidsNitrogenous substances
Generalised picture The cell is a living structure, thus is only possible to show a
general picture. Remember – that cells constantly move and change
The Cell Revised
‘Protein factories’ of the cell
Structures within the cell
Cytoplasm
Mitochondria
Ribosomes
Protoplasm inside the cell but outside the nucleus
Organelles - referred to as the ‘power houses’
The Cell Revised
Organelles containing digestive enzymes
Structures Cont.
Endoplasmic reticulum
Golgi apparatus
Lysosomes
‘Circulatory system’ of a cell Two types:
Rough Smooth
Communication network from deep within the cells to its membrane Also used to make Lysosomes
The Cell Revised
Dense areas of cytoplasm containing the Centrioles
Structures Cont.
Vacuoles
Centrioles
Centrosomes
Used for storage or digestive purposes in different types of cell
Paired, rod-like organelles which play an important role in mitosis
The Cell Revised
The point where two chromatids join in the chromosome
Structures Cont.
Nucleus
Chromatids
Centromere
Largest organelle Controls the cells processes
Two strands of DNA held together by a centromere form a chromosome
The Cell Revised
Chromatin – A combination of DNA and proteins that makes up chromosomes.
Structures Cont.
Nucleolus
Chromosomes
Chromatin
Programmes the formation of ribosomes which then move into the cytoplasm of the cell and produce protein
Chromosome is an organized building of DNA and protein that is found in cells
The Cell Revised Structures Cont.
Nucleoplasm
Specialised protoplasm, in which the nucleoli and Chromatin/chromosomes are suspended along with Nutrients and other necessary chemicals
Structures finished
Cells MembraneThe Cell Revised
A thin semi-permeable membrane made of protein threads and lipids Two functions
To act as a regulator To exchange harmful products
Fluid inside is called – Intracellular fluidFluid outside is called – Extracellular fluid
Not all substances can cross through the cell membrane
TYPES OF MOVEMENT ACROSS THE CELL MEMBRANE
The Cell Revised
Passive Transport The movement of molecules across the cell membrane and does not require energy
There are four main kinds
Diffusion Osmosis Dissolution Filtration
TYPES OF MOVEMENT ACROSS THE CELL MEMBRANE
The Cell Revised
Diffusion
The movement of molecules from a region of higher concentration to a region of lower
concentration.
OsmosisProcess of transferring water across the
membrane is by
Equal pressure on both sides of the membrane
Isotonic pressure
Osmotic pressure
TYPES OF MOVEMENT ACROSS THE CELL MEMBRANE
The Cell Revised
Dissolution
Movement of water and soluble substances across a membrane.
Filtration
Hydro-static pressure
Substances can diffuse directly through the lipid bi-layer part of the membrane
TYPES OF MOVEMENT ACROSS THE CELL MEMBRANE
The Cell Revised
Active transport Energy is used When too large Not soluble on fat
The pumping of substances across a membrane by a trans-membrane protein
pump molecule
Cell ReproductionThe Cell Revised
Mitosis
The process at which cell reproduce Exact replicas of chromosomes in parent cells are duplicated to form daughter cells
Consists of four main stages
Anaphase Metaphase
Prophase
Telophase
Interphase Normal metabolic functions DNA is reproduced Nuclear protein is synthesised Cell increases in size
Cell ReproductionThe Cell Revised
Metaphase
ProphaseCentrosomes divide into two CentriolesThe chromatin in the cell’s nucleus shortens and thickens Two visible pairs of rods called chromosomes are formedThe nucleolus disappears
The chromosomes arrange themselves at the centre of the cellEach individual chromosome can be seen distantly as two chromatids
The nuclear membrane disappears
Cell ReproductionThe Cell Revised
Telophase
Anaphase Centromere stretches Pairs of chromatids divideSpindle threads of the Centrioles divide to form new centromeres Cell membrane begins to constrict
Spindle fibres disintegrate and Centrioles replicate Membrane continues to constrict
Nuclear membrane appears
Two daughter cells are formed
Tissue types
Four types of tissue:
Epithelial Connective Nervous Muscular
Tissue types
Epithelial tissue (or Epithelium)
Simple epithelium - usually functions as a covering or lining for organs and vessels
Compound epithelium - provides external protection and internal elasticity
Tissue typesSimple Epithelium
Consists of a single layer of cells attached to a basement membrane Goblet cells often found in simple epithelium Four types of simple epithelium: Squamous Cuboidal Columnar Ciliated
Squamous Flattened cells Forms thin, often permeable lining Allows diffusion and filtration
Tissue typesCuboidal
Cube-shaped cells Forms lining of kidney tubules as well as some glands
Columnar Tall, rectangular cells Forms lining in very active parts of the body such as the stomach intestines and urethra; some cells secrete mucus and some absorb mucus
Ciliated Mostly columnar cells Tiny hair-like projections, or cilia, stick out from the cell membrane The cilia work in waves Help to remove mucus, foreign matter and debris
Tissue types
Compound epithelium
Many layers of cells and no basement membrane Formed from a combination of deep layers of columnar cells plus flatter cells towards the surface Protects and delicate parts of the body Two types of compound epithelium:
StratifiedKeratinised (dry) – surface layer
Non-keratinised (wet)
Transitional
Tissue typesStratified
Keratinised (dry)o Surface layer has dried out into keratin,o Compound epithelium with dry surface cells o Forms a dead layero The skino keratinisation
Non-keratinised (wet)o Compound epithelium with wet surface cellso Provides lubrication
Transitional o Similar to stratified epitheliumo Surface cellso Deeper cellso Found in organs that need waterproof and expandable lining
Tissue typesNervous tissueo Arranged in bundles of fibreso Composed of nerve cells and neurogliao Have long fibrous processes – called dendrites and axonso Capable of transmitting signals to and from the brain – protective
Muscular tissue Three types:
Skeletal – striated and voluntary – support and movement
Smooth - non-striated and involuntary – carry out involuntary movements
Cardiac – striated and involuntary – heart muscle to pump blood
Tissue typesConnective tissue Supporting tissue of the body Mostly mechanical functions and connect more active tissues Can be semi-solid, solid or liquid – can have fibres present or not Mainly mechanical connecting other more active tissues
There are eight types:
Areolar Adipose White Fibrous
Lymphoid Yellow Elastic
Blood Bone
Cartilage
Tissue types AreolarLoose connective tissueMost general connective tissueSemi-solid and permeable Contains yellow elastic and white fibres, fibrocytes and mast cellsFound all over the body
Adipose Known as fatty tissue Made up of fat cells containing fat globules Found between muscle fibres and under the skin Also found in the kidneys and the back of the eyes Protective and insulator properties
Tissue types
White Fibrous Strongly connective Closely packed bundles of collagen fibres Few cells in rows that run in the same direction Function is connection and protection of parts of the body
Lymphoid Semi-solid tissue Majority of cells are lymphocytes and reticular cells which have a disease control function Forms lymphatic system cells and blood cells Protects against disease
Tissue types
Yellow elastic Composed of elastic fibres Enables stretch and capable of considerable extension and recoil Forms lung tissue, bronchi and trachea, arteries, stomach and bladder
Bone Hardest structure in the body; Two types – compact and cancellous Compact is dense bone for strength Cancellous for structure bearing and cellular development Composition – 25% water, 30% organic material, 45% inorganic salts Supports and protects the body and all organs, also produces cells in bone marrow
Tissue types
Blood Fluid connective tissue Contains 45% cells and 55% plasma Cell content is erythrocytes, leucocytes and thrombocytes Transports food , oxygen and waste to and from the body
Cartilage Firm, though tissue; solid Contains cells called chondrocytes
Three types Hyaline Yellow elastic cartilage White fibro-cartilage
Tissue types
Hyaline
Bluish – white, smooth; Chondrocytes cells are grouped together in nests in a solid matrix Particularly resilient Connects and protects Found on articular surfaces of joint Bone which forms joints
Yellow elastic cartilage:
Runs through a solid matrix Contains fibrocytes and chondrocytes cells which Lie between multidirectional fibres Flexible in areas of need
Tissue types
White fibro-cartilage While fibres Contains chondrocytes cells Extremely tough and slightly flexible Absorbs shock Example – forms intervertebral discs as well as the semi-lunar cartilages (menisci)