Animal Specialized Structures and Tissues

Animal Specialized Structures

• Tissues are formed from differentiated cells.
• The human body consists of over 200 different types of cells.
• Histology is the study of animal and plant tissues.
• Four main tissue types in animals are epithelial, connective, muscle, and nervous.

Epithelial Tissues

• Epithelial tissue can be simple (one layer) or stratified (multiple layers).
• Simple epithelium is a single layer of cells.
• Stratified epithelium has more than one layer of cells.
• Types of epithelium include squamous (flat), cuboidal (cube-shaped), and columnar (column-shaped).

Connective Tissues

• Connective tissues are characterized by a large extracellular matrix.
• The extracellular matrix can be solid, soft, or liquid. Examples include bone, soft connective tissue, and blood.
• The primary function of connective tissues is to bind and support other tissues.
• Connective Tissues are classified into three groups: connective tissue proper, supportive connective tissue, and fluid connective tissue.
• Connective tissue proper includes loose, dense, reticular, and adipose connective tissues.
• Loose connective tissue (also called areolar) has a watery matrix where fibroblasts and other cells reside.
• Dense connective tissue is made of closely packed bundles of collagen fibers.
• Reticular connective tissue is composed of reticular cells and fibers, providing support for soft organs.
• Elastic connective tissue is highly flexible and contains elastic fibers and collagen fibers.
• Adipose tissue is a specialized connective tissue that stores fat.
• Supportive connective tissue includes cartilage and bone.
• Cartilage contains chondrocytes in a matrix of chrondrin.
• Bone contains osteocytes in a mineralized matrix with collagen fibers.
• Fluid connective tissue includes blood.
• Blood is a fluid connective tissue with a liquid matrix (plasma).
• Blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Muscle Tissues

• Muscle tissues are contractile tissues that enable movement.
• Muscle tissues contain muscle fibers.
• Three types of muscle tissue are skeletal, cardiac, and smooth.
• Skeletal muscle tissues attach to bones and are responsible for locomotion. Their contractions are voluntary.
• Cardiac muscle tissue is found only in the heart and pumps blood. Its contractions are involuntary.
• Smooth muscle tissue is found in the walls of internal organs and blood vessels and are involuntary.

Nervous Tissues

• Nervous tissue is made up of neurons (nerve cells).
• Neurons are found in the brain and spinal cord.
• Each neuron has three main parts: dendrites, cell body, and axon.
• Dendrites receive impulses and convey them to the cell body.
• The cell body contains the nucleus and organelles.
• The axon transmits impulses away from the cell body to other neurons.

Plant Specialized Structures

• Vegetative organs include roots, stems, and leaves.
• Roots anchor plants to the soil and absorb water and minerals.
• Stems are the main axis of the plant and distribute the products of photosynthesis.
• Leaves carry out photosynthesis to produce food.

Plant Tissues

• Two main types of plant tissues are meristematic and permanent.
• Meristematic tissue is responsible for plant growth.
• Meristems are embryonic tissues made of meristematic cells.
• Meristems are found in areas of fastest growth.
• Permanent tissues are created from meristem tissues
• Permanent tissues are further divided into three classes: surface, fundamental, and vascular.
• Surface tissues (also called dermal tissues) cover and protect plant organs. The epidermis is an example of a surface tissue.
• Fundamental tissues (also called ground tissues) form the main bulk of the plant.
• Fundamental tissues are composed of three types of cells: parenchyma, collenchyma, and sclerenchyma.
• Parenchyma cells are large, thin-walled, and are responsible for food storage and are also capable of cell division.
• Collenchyma cells function primarily for support. They are similar to parenchymal cells, but have thicker cell walls.
• Sclerenchyma cells have a thick secondary cell wall made of lignin, providing support and strength.
• Vascular tissues (xylem and phloem) are complex conducting tissues in plants and extend to all parts of the plant.
• Xylem transports water and minerals from roots to shoots.
• Phloem transports sugars and other organic nutrients throughout the plant. Phloem often sits outside of xylem.