Cells, Organs and Organisms

By Stella Angeli and Charles Maseela

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Specialized Tissues• Epithelial Tissue:-

– Squamous: Forms alveoli of respiratory membrane and endothelium of capillaries.

– Columnar: Lines the small intestine. Has unicellular glands called goblet cells scattered throughout its structure that secrete mucus.

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Specialized Tissues 2• Muscle Tissue:-

– Skeletal muscle: Affects skeletal movement such as locomotion and maintaining posture. Reacts to conscious control.

– Smooth muscle: Found in the walls of organs. Involuntary movement, not under conscious control.– Cardiac Muscle: Involuntary muscle, found only in the heart.

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Specialized Tissues 3– Nervous Tissue:-

– Unipolar neurones: sensory neurones that have only a single process or fibre which divides close to the cell body into two main branches (axon and dendrite).

– Bipolar neurones: Spindle shaped with a dendrite at one end and an axon at the other (e.g. light-sensitive retina of the eye).

– Multipolar neurones: Motor neurones which have numerous cell processes (an axon and many dendrites).

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Organs• Specialized tissue comes together to form structures called organs. Each

organ is specialized to carry out a specific task, e.g.:– Epithelial tissue comes together to form the lining of the lungs and the endothelial lining of blood

vessels in the respiratory system as well as the lining in the intestines of the digestive system.– Muscle tissue comes together to form support for the skeleton and is the basis for movement in the

body (voluntary and involuntary).– Nervous tissue comes together to form the central nervous system (the brain and spinal cord) and

has a fundamental role in the control of behaviour and bodily processes (voluntary and involuntary).

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Organisms• Organ systems come together to form organisms with each organ system performing a certain

task, vital for the organism’s survival.• In humans the various organ systems come together, with each organ system dependant on the

others for the organism to survive:-

– Digestive system: Absorption of nutrients and excretion of waste.

– Skeletal system: Support, lymphocyte production.

– Muscular system: Support and movement, production of heat.

– Nervous system: Integration, coordination and regulation through electrochemical signals.

– Endocrine system: Integration, coordination and regulation through hormones.

– Respiratory system: Elimination of CO2 and absorption of O2 .

– Circulatory system: The transporting of needed materials to the cells and the transporting of wastes away from the cells.

– Reproductive system: Production of offspring.

– Integumentary system: Body covering.

– Lymphatic system: Regulate fluids and immunity.

– Urinary system: Excretion of nitrogenous waste, and maintain homeostasis of electrolytes.

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