Plant and Animal Tissues: Types, Functions and Structure

Plant Tissues

Parenchyma

Parenchyma cells make photosynthesis in the stems and green parts of plants. Varieties: palisade and spongy.

Cambium and Cork Cambium

Both are secondary meristems. The internal cambium and the vascular cambium produce conducting tissues: towards the center, xylem (secondary xylem); outwards, phloem (secondary phloem). The cork cambium produces external cork tissue and the internal phelloderm, which travel towards the parenchyma cortex.

Collenchyma

Collenchyma cells are found in young parts of plants. They are vivid, elongated, prismatic cells containing chloroplasts, with thickened walls in layers. There are 3 types: angular, lamellar and lacunar.

Secretory Tissues

External

Located in the epidermis, they expel foreign substances. Types:

• Nectaries (expel nectar)
• Hydathodes (expel water)
• Urticant hairs (expel irritant chemicals)

Internal

Located inside the plant, they accumulate elaborated substances. Types:

• Laticifers (latex tubes): living cells, longer, branched and multinucleate, accumulating latex inside.
• Resiniferous canals: elongated cavities that accumulate resin.

Animal Tissues

Connective Tissue

Large cells, of the following types:

• Fibroblasts (irregular, produce fibers)
• Macrophages (amoeboid, engulf chemicals)
• Mast cells (spherical)
• Adipocytes (store fat)

Blood tissue includes lymphocytes and plasma cells.

Muscle Tissue

Skeletal Muscle

Forms skeletal fibers, cylindrical, long, multinucleate. Contractions are rapid and voluntary.

Cardiac Muscle

Found in the heart walls. Cells are elongated, with striations and one or two central nuclei. Contractions are rapid and involuntary.

Smooth Muscle

Forms the walls of the digestive and respiratory organs. Contractions are slow and involuntary.