Final answer:
Substances that can transfer from blood to interstitial tissues include oxygen, glucose, hormones, small hydrophobic molecules, water, inorganic ions, and small organic substances like amino acids and urea. Continuous capillaries facilitate the transfer of these substances, while leukocytes can traverse the endothelium to aid in immune responses.
Step-by-step explanation:
Substances that can be transferred from the blood to the interstitial tissues include a variety of small molecules and nutrients necessary for cellular function. Oxygen, glucose, and other metabolic products freely pass through the pores and intercellular clefts in the capillary endothelium. Likewise, small hydrophobic molecules like certain gases (for example, carbon dioxide as a waste product) and hormones can also diffuse from the blood to the interstitial fluid.
Additionally, while proteins and other large solutes cannot leave the capillaries, water, inorganic ions, and other small organic molecules such as amino acids, and urea are capable of moving across the capillary barrier via diffusion or active transport.
Transport vesicles in continuous capillaries significantly contribute to the movement of substances through processes like endocytosis and exocytosis. Furthermore, various leukocytes can exit the blood vessels to enter interstitial spaces, playing a crucial role in immune responses. It is important to note, however, that in brain tissues, this transfer is highly regulated due to the presence of the blood-brain barrier, which restricts the movement of nearly all substances.