specialised cells

• specialised cells have a specific function / adapted to their function
• the cells that line the small intestine absorb small food molecules produced by digestion. they are adapted by having membranes with many tiny folds called microvilli. These adaptations increase the surface area of the cell. the more area for molecules to be absorbed, the faster absorption happens
• cells in the pancreas make enzymes needed to digest certain foods in the small intestime
• the enzymes are proteins and so these cells are adapted by having a lot of ribosomes.
• the wall of the small intestine has muscles to squeeze food along. the muscle cells require a lot of energy and are adapted by having many mitochondria
• during sexual reproduction, two specialised cells / gametes / fuse to create a cell that develops into an embryo
• human gametes are the egg cell and the sperm cell
• most human cell nuclei contain two copies of the 23 chromosomes. games contain 1 copy. this means the cell produced by fertilisation has two copies.
• cells with two sets of chromosomes are diploid and cells with one set are haploid
• adaptions of a human female gamete: large surface area, large number of mitochondria, large nucleus

  
• adaptions of a human male gamete: large head, large nucleus, large mitochondria

  
• sperm


  tip of head contains small vacuole - acrosome which contains enzymes that break down substances in the egg cells jelly coat allowing the sperm to burrow inside
• sperm

  large number of mitochondria are arranged in a spiral around the top of the tail, to release lots of energy to power the tail.
• egg


  the cell membrane fuses with the sperm cell membrane. after fertilisation the cell membrane becomes hard to stop other sperm cells entering
• egg


  the cytoplasm is packed with nutrients to supply the fertilised egg cell with energy and raw materials for the growth and development of the embryo
• the jelly coat protects the egg cell. it also hardens after fertilisation, to ensure that only one sperm cell enters the egg cell
• fertilisation occurs in the oviducts of the female reproductive system.
• cells in the lining of the oviduct transport egg cells towards the uterus
• the oviduct cells are adapted for this function by having hair like cillia
• cilia are like short sperm cell tails and wave from side to side to sweep substances along.
• cells that line structures in the body are called epithelial cells and these cells with cilia are called ciliated epithelial cells
• function of a gamete?


  fuse together during fertilisation to create a cell that will develop into an embryo
• function of cilia


  to move fertilised egg cells towards the uterus
• explain how cells that line the oviduct are adapted to their function of moving the egg cell

  they are adapted by having hair like cilia that sweep the egg cell towards the uterus.