A2.2.9

• Red Blood Cells (Atypical Cell Structure):

  In mammals they don’t have a nucleus. It is removed at a late stage in their development however it makes them smaller and more flexible. They cannot repair themselves if they are damaged and they life 100 to 200 days.
• Phloem sieve tube elements (Atypical cell structure):

  If the cells would have a typical structure, the flow of sap wouldn’t work, so they are hollow.

  In phloem, the vessels that conduct sugary sap from the leaves to other parts are called sieve tubes. They have large pores for the sap to pass through.

  The sieve elements lack nuclei and have few organelles, they rely on companion cells for survival.
• Skeletal Muscle (Atypical Cell Structure):

  Muscle fibres develop when groups of cells fuse together. Columns of cells are formed by cell division. These then fuse together to form long muscle fibres.
• Aseptate fungal hyphae (Atypical Cell structure):

  Hyphae are used for nutrient absorption and growth. Hyphal cells are separated by internal walls called septa, but some hyphae are not partitioned and have a continuous cytoplasm with multiple nuclei.