Specialised cells

• Tissue

  A collection of differentiated cells that together have a specialised functions in an organism.
• Organ

  Forms a distinct structural and functional unit within an organism that is made from more than 1 tissue.
• Organ System

  A collection of organs with a particular function.
• Spermatozoa function:

  Fuse with an egg to deliver genetic information
• Spermatozoa features:

  • Flagellum providing motility to swim to the egg
  • Many mitochondria to provide ATP for swimming
  • Acrosome on the head contains digestive enzymes to penetrate the outside of the egg during fertilisation
• Erythrocytes function:

  Transporting oxygen around the body
• Erythrocytes features:

  • Flattened, biconcave shape: increases surface area for transporting oxygen around the body.
  • No nucleus: space saving, more haemoglobin.
  • Flexible: squeeze through narrow capillaries.
• Palisade Cells

  • Found in the mesophyll layer
  • Contain numerous chloroplasts to absorb light or photosynthesis.
  • Rectangular shaped: forms a continuous layer for maximal light absorption.
  • Thin cell walls: reduce diffusion distances of carbon dioxide.
  • Large vacuole: maintain turgidity.
• Root hair cells

  • Found at the surfaces of the root within the epidermis.
  • Have long extensions(root hairs): increase the surface area for absorption of water & mineral ions from the soil.
• Guard Cells

  • Found in pairs on the lower epidermis of the leaves.
  • Form small pores called ‘Stomata’.
  • Stomata: site of gaseous exchange in plants.
  • inner cell wall is thicker and rigid.
  • When the cell is turgid the cell changes shape by curving causing the stomatal pore to open.
• types of animal tissue


  1. Nervous tissue: adapted to support the transmission of electrical impulses around the body.
  2. Epithelial tissue: adapted to cover the body surfaces, internal and external.
  3. Muscle tissue: adapted to contract.
  4. Connective tissue: adapted to either hold other tissues together or as a transport medium.
• Squamous epithelium

  • Made of squamous epithelial cells.
  • ‘Pavement epithelial’ flat.
  • One cell thick.
  • very thin & smooth
  • has a basement membrane which holds the epithelium on to the other tissues
  • Found where rapid diffusion across an exchange surface is necessary – e.g. Lining of the alveoli walls
• Ciliated epithelium

  • Made of ciliated epithelial cells.
  • Cells have ‘hair like’ structures (cilia) on one surface that ‘beat’ in a synchronised pattern to move materials along.
  • E.g. mucus in the airways and the egg in the oviduct.
  • Often they are associated with glandular tissue/cells that secrete mucus (goblet cells).
  • Columnar cells are long and column like.
• Connective tissue – Cartilage


  • Connective tissue found on the outer ear, nose, airways and lining the ends of bones.
  • firm and flexible connective tissue made of chondrocyte cells embedded in an extra-cellular matrix.
  • The matrix consists of collagen fibres (strength) and elastin fibres (flexibility).
• 3 forms of cartilage:


  Hyaline (Ends of bones / airways/ nose)

  Fibrous (vertebrae discs)

  Elastic (outer ear)
• Muscle

  • Function is to move parts of the body.
  • Bring about movement by being able to shorten (contract).
  • Muscle fibres contain contractile proteins called myofilaments.
  • Muscle is well vascularised.
• 3 forms of muscular tissue:

  1. Skeletal – joined to bones.
  2. Cardiac – makes up the wall of the heart.
  3. Smooth – makes up the walls on the intestines, blood vessels, airways, uterus and urinary tracts.
• 2 main groups of plant tissue:

  1. Epidermis tissue – adapted to cover plant surfaces.
  2. Vascular tissue – Adapted for transport of water and nutrients.
• Epidermis

  • Made of epidermal cells – lack chloroplasts.
  • Flat.
  • Made of a single layer of closely packed cells which provide a protective covering on leaves, stems and roots.
  • Often covered in a waxy cuticle.
  • Found with guards cells forming stomata on the lower epidermis of leaves for gaseous exchange.
• Vascular Tissue - Xylem

  • transport tissue that carries water and minerals from the roots to the rest of the plant.
  • consists of hollow columns of elongated dead cells lined end to end and reinforced with lignin.
  • Lignification strengthens the cell wall &ensures that the xylem vessels do not collapse.
• Vascular tissue - Phloem

  • transport tissue that carries the products of PS e.g. sucrose to the rest of the plant.
  • consists of sieve tube elements and companion cells.
  • Sieve tubes forms columns of stacked cells with perforated end walls called ‘Sieve plates’.
  • Companion cells actively load sucrose into the phloem tubes for transport.
• xylem summary

  • dead
  • transports water & minerals up the plant
  • one way flow
  • no end walls
  • no cell contents
  • no companion cells
  • tubular vessel
• phloem summary

  • living
  • transports sugar up and down the plant
  • two way flow
  • end walls adapted as sieve plates
  • few contents with thin layer of cytoplasm
  • possess companion cells to carry out metabolic processes & actively load sugar
  • tubular vessel
• organs: mammalian heart

  • pumps blood around the body.
  • Contains tissues – muscle, blood, nervous and connective.
• organs: leaf

  • photosynthesis
  • Contains tissues – vascular and epidermis.
• animal organ systems:

  • Digestive System
  • Cardiovascular System
  • Gaseous Exchange System
  • Immune System
• plant organ systems:


  • Shoot system: above ground - leaves, stem, flowers and fruits, absorb light needed for photosynthesis.
  • Root system: underground – supports the plant and supplies water and minerals to the parts of the plant above ground.
• Neutrophil cells

  Multi-lobed nucleus so can squeeze through small gaps to access site of infection

  Granular cytoplasm- full of lysosomes for the break down of engulfed pathogens
• Palisade cells

  Located in the mesophyll tissue layer of leaves

  Contains numerous chloroplasts to absorb light for photosynthesis

  Large vaculole to maintain turgidity

  Thin cell wall to reduce diffusion distances of CO2

  Rectangular shaped to form a continuous layer for maximal light absorption