Final answer:
Nuclear pores are holes in the nuclear envelope that regulate the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm, playing a key role in cell functionality.
Step-by-step explanation:
The holes in the nuclear envelope that allow substances to get into and out of the nucleus are known as nuclear pores. These structures are essential for the regulation of the exchange of materials such as ions, molecules, and RNA between the nucleoplasm and the cytoplasm. The nucleoplasm is the semi-solid fluid inside the nucleus, containing elements such as chromatin and the nucleolus. The nuclear envelope itself is a double-membrane structure made up of two phospholipid bilayers with the outer membrane being continuous with the rough endoplasmic reticulum. Nuclear pores are complex protein assemblies that act as gatekeepers, ensuring that only the correct substances can pass through, playing a crucial role in processes such as protein synthesis and the maintenance of genetic material within the nucleus.