2. Stem cells retain the ability to specialize, and enable tissues to grow and heal.
3. Epithelium is lining tissue. It may be simple (one layer), stratified (more than one layer), or pseudostratefied(one layer appearing as more than one). Epithelial cells may be squamous(flat), cuboidal(cube shaped), or columnar(tall and thin). Keratin hardens squamous epithelium. Epithelial tissue protects, senses, and secretes.
4. Connective tissues consist of cells within a matrix. Fibroblasts secrete collagen and elastin. Loose connective tissue has tightly packed collagen fibrils. Adipose tissue consists of adipocytes swelled with lipid. The matrix of blood is plasma, which carries red blood cells, white blood cells, and platelets. Cartilage consists of chondrocytes in lacunae, in a collagen matrix. In bone, osteocytes communicate through canaliculi. Osteoclasts and osteoblasts tear down and rebuild bone tissue. Osteoprogenitor cells can become osteoblasts. Bone matrix consists of collagen and minerals.
5. Neurons and neuroglia constitute nervous tissue. A neuron has a cell body, an axon, and dendrites and functions in communication. Neuroglia support neurons.
6. Muscle tissue provides movement when filaments of actin and myosin slide past one another. Contractile cells include skeletal, cardiac, and smooth muscle cells.
30.2 Tissues and Organs Build Animal Bodies
7. The nervous and endocrine systems coordinate all others, via neurotransmitters and hormones.
8. The skeletal and muscular systems provide support and locomotion.
9. The respiratory system obtains oxygen and the circulatory system delivers it to tissues, where it is used to extract maximal energy from nutrient molecules. The digestive system provides nutrients.
10. The integumentary system provides a physical barrier between an animal and its surroundings.
11. The urinary system removes wastes from the blood and reabsorbs useful substances.
12. The immune system protects against infection, injury, and cancer.
13. The reproductive systems are essential for the perpetuation of an individual's genes.
30.3 Organ System Interaction Promotes Homeostasis
14. Homeostasis is the maintenance of internal constancy
15. Negative feedback reduces or increases the level of a substance or parameter to within a normal range.
16. The integument in many animals consists of an epidermis over a dermis, plus specialized structures, such as hairs, feathers, claws, and glands. A basement membrane joins the epidermis to the dermis, and a subcutaneous layer underlies the dermis. Melanocytes provide pigment.