Tissue Types and Functions in Human Biology

Skeletal Muscle

• Action of parallelly sustained contraction allowing voluntary movement.
• Characteristics:
  • Striated appearance due to transverse bands (dark and light bands).
  • Under conscious control (voluntary).
  • Attached to the skeleton (bones).
• Structure:
  • Multinucleated; each muscle fiber contains multiple nuclei.

Smooth Muscle

• Characteristics:
  • Involuntary (not under conscious control).
  • Located in internal organs, such as the digestive tract and blood vessels.
  • Non-striated (lacks light and dark bands).
• Structure:
  • Uninucleated; each muscle cell has a single nucleus.
  • Spindle-shaped cells found in digestive organs and blood vessels.
• Example of Function:
  • Swallowing process:
  • Voluntary action in the mouth; involuntary action begins in the esophagus.
  • Once food enters the esophagus, movement is controlled by an involuntary mechanism (peristalsis).
  • Peristalsis is the involuntary movement that pushes food down towards the stomach.
  • Cannot interrupt the food's progress through the esophagus voluntarily.

Cardiac Muscle

• Characteristics:
  • Mixed muscle type.
  • Striated like skeletal muscle.
  • Uninucleated similar to smooth muscle.
  • Involuntary control.
• Structure:
  • Contains an intrinsic mechanism for rhythmic contraction and relaxation.
  • Has intercalated discs connecting individual muscle fibers.
• Functions:
  • Maintains the rhythmic pumping action of the heart.
  • Myocardium: the thick, muscular layer of the heart with a robust blood supply.
  • Endocardium: the inner lining made of endothelial cells.
  • Intercalated discs facilitate rapid conduction of contraction impulses across fibers.

Nervous Tissue

• Composition:
  • Made up of nerve cells (neurons) and fibers.
  • Neurons: conducting cells that transmit impulses.
• Structure of Neurons:
  • Cell body (soma) contains the nucleus and organelles.
  • Dendrites: short fibers that receive information from surrounding cells, acting as receptors.
  • Axon: long fiber that transmits impulses away from the cell body.
  • Myelin sheath: a fatty insulating layer that speeds up impulse transmission by allowing it to jump between Nodes of Ranvier.
• Neuron Types:
  • Motor neurons: transmit messages away from the nerve cell.
  • Sensory neurons: transmit messages towards the nerve cell.
• Functions:
  • Neurons have irritability (responding to environmental changes) and conductivity (transmission of impulses).
  • Allow perception, control emotions, reasoning, and memory storage.
  • Help coordinate body activities.
• Supporting Cells:
  • Neuroglial cells: make up the majority of brain tissue.
  • Provide support, supply nutrients, and protect nerve cells.
  • Name breakdown: "neuro" (nerve) + "glia" (glue).

Other Relevant Concepts

• Cell Size Change:
  • Changes in size or shape may indicate cancerous conditions.
  • Mutation from normal to irregular arrangement can lead to tumor formation.
• Muscle and Nervous System Interaction:
  • Skeletal muscles (controlled by the nervous system) facilitate body movements.
  • The cerebellum helps balance through coordination and processing position data from ears.
  • Connective tissues like fascia surround and protect muscles (aponeurosis and tendon).
• Glands:
  • Exocrine and endocrine glands discussed, including mammary glands (complex gland).
• Functional Roles:
  • Sebaceous and sweat glands maintain skin moisture and temperature.
  • Osteocytes are present in bones; thrombocytes are in cartilage.
• Kidneys:
  • Principal role in filtering blood and maintaining fluid balance and producing vitamin D.