Cell

• Mitochondria are the powerhouses of the cell, producing energy through cellular respiration.
• Parenchyma is a type of simple permanent tissue that makes a major part of ground tissues in plants, where other tissues like vascular tissues are embedded
• Some of the important functions of parenchyma cells in plants are: 1. Stores food and nutrients. 2. Provides support and foundation. 3. Provide mechanical rigidity to the plants 4. They are the site of all metabolic activities.
• Some of the important functions of parenchyma cells in plants are:

  1. Stores food and nutrients.

  2. Provides support and foundation.

  3. Provide mechanical rigidity to the plants

  4. They are the site of all metabolic activities.
• Chlorenchyma makes up the mesophyll tissue of plant leaves
• Palisade Chlorenchyma are located in the leaves, right below the epidermis and cuticle
• Spongy chlorenchyma is found between the palisade layer and the lower epidermal layers of the leaf
• Living organisms in this world comprise of cells
• Unicellular organisms have a single cell capable of performing functions like respiration, digestion, and clearing of the cell
• In multicellular organisms, there is a division of labour with different types and groups of cells performing various functions
• Examples of cell functions in animals:

  • Muscle cells cause movement
  • Nerve cells carry messages and signals
  • Blood transports food and oxygen to different body parts
• In plants, vascular tissues carry food and water to different plant parts
• Formation of tissues:

  • Cells that need to perform a single task group together to form tissues
  • Tissues consist of cells with the same origin and function
• Classification of Animal Tissues:

  • Epithelial Tissue:
  • Protective tissues covering organs and cavities
  • Found in blood vessels, mouth lining, skin, lung alveoli, etc.
  • Functions as a barrier separating organs and systems
  • Types: Simple Epithelium and Stratified Epithelium
• • Cuboidal or columnar cells with cilia for material transport
  • Locations: oviduct, trachea, pharyngeal region, uriniferous tubule
• Types of Epithelial tissues based on structure:

  • Simple Epithelium:
  • Squamous Epithelium:
  • Single layer of flat, thin cells with centrally located nucleus
  • Locations: blood vessels, skin, esophagus, mouth lining, alveoli, kidney nephron
  • Cuboidal Epithelium:
  • Cuboidal cells involved in absorption and secretion
  • Locations: thyroid gland, sweat gland, hepatic duct, uriniferous tubule
  • Columnar Epithelium:
  • Longer cells for absorption in small intestine
  • Locations: inner lining of small intestine, reproductive organs
  • Ciliated Epithelium:
• Stratified Epithelium:

  • Multilayered tissue for protection
  • Innermost layer is living and divisible (Germinative layer)
  • Deposition of keratin makes it resistant to water and abrasions
  • Locations: epidermis of skin, lining of rectum
• Connective Tissues:

  • Number of cells in connective tissue is very less
  • Loosely bound cells in an intercellular matrix
  • Types: Fluid/Liquid Connective Tissue, Skeletal Tissue, Connective Tissue Proper
• Examples of Connective Tissues:

  • Fluid Connective Tissues:
  • Blood:
  • Transports gases, food, waste materials, and hormones
  • Contains plasma, RBC, WBC, platelets, proteins, and hormones
  • Lymph:
  • Colorless fluid carrying white blood cells
  • Functions: transport, immunity, fat absorption
  • Skeletal Connective Tissues:
  • Bones and Cartilage forming the skeleton
  • Functions: endoskeleton, muscle attachment, organ protection
• Cartilage:

  • Present over the joints of the bones and provides them with a smooth structure
  • Found in the nose tip, ear pinna, trachea, and larynx
  • Contains a solid matrix made of protein and sugar
  • Provides support and flexibility to various parts of the body
• Ligaments:

  • Connect two bones together
  • Have elasticity that facilitates the connection
  • Cells have a little matrix
• Tendons:

  • Connect bones and muscles together
  • Have limited flexibility but great strength
• Differences between Tendons and Ligaments:

  Tendons:

  • Connect skeletal muscles to bones
  • Tougher and less elastic
  • Connect the end of the muscles to bones
  • Fibers are compact and present in parallel bundles

  Ligaments:

  • Connect bones to bones
  • More elastic
  • Connect the end of the bones at joints
  • Fibers are not arranged in parallel bundles but are compactly packed
• Areolar connective tissue:

  • Acts as a filter between spaces inside the body organs
  • Helps in repairing other tissues
  • Found in the skin and bone marrow
  • Found in the walls of the alimentary canal and arterial walls
  • Components include fat cells (adipocytes), fibroblasts, mast cells, macrophages, and plasma cells
• Fibres:

  • Collagen Fibres provide tensile strength to the tissue
  • Elastin Fibres provide elasticity to the tissue
  • Ground Substance is a fluid matrix that holds cells and fibres of the tissue
• Adipose:

  • Fats are stored in adipose tissues
  • Found below the skin and between organs
  • Provides cushioning to the organs
• Muscular Tissue:

  • Made up of long cells called muscle fibres
  • Cells have contractile proteins causing muscle contraction and relaxation
  • Can be voluntary or involuntary muscles
  • Three basic types: Skeletal Muscles, Visceral Muscles, Cardiac Muscles
• Skeletal Muscles:

  • Voluntary muscles attached to bones
  • Cells have more than one nucleus and are unbranched
  • Covered by Sarcolemma and contain mitochondria and glycogen granules
  • Present in voluntary organs like muscles of hands, legs, tongue, etc.
• Visceral Muscles:

  • Involuntary muscles found in the alimentary canal and Iris of the eyes
  • Cells are long and spindle-shaped with slow contraction and relaxation
• Cardiac Muscles:

  • Special involuntary muscles found in the heart
  • Perform rhythmic contraction and relaxation without fatigue
  • Cells are cylindrical with a single nucleus and branched
• Nervous Tissue:

  • Found in nerves, brain, and spinal cord
  • Made up of nerve cells or neurons
  • Neurons connect to form nerves
  • Functions involve receiving, processing, and responding to internal and external environment
• Structure of a Neuron:

  • Cell Body with Dendrites and Nucleus
  • Nerve Endings connected via Axon
  • Neurons can be up to 1m long
  • Neurons surrounded by neurilemma
  • Schwann Cells produce myelin sheath
• Synapse:

  • Gap between two nerve endings
  • Conduction of nerve impulse occurs through neurotransmitters like acetylcholine, dopamine, GABA, etc.
• Living organisms in this world comprise of cells
• Unicellular organisms have a single cell capable of performing functions like respiration, digestion, and clearing of the cell
• In multicellular organisms, there is a division of labour with different types and groups of cells performing various functions
• In animals, muscle cells cause movement, nerve cells carry messages, and blood transports food and oxygen
• In plants, vascular tissues carry food and water to different parts of the plant
• Tissues are formed when cells group together to efficiently perform a specific function
• Epithelial Tissue:

  • Protective tissues covering organs and cavities
  • Found in blood vessels, mouth lining, skin, lung alveoli, etc.
  • Cells are compactly arranged with no intercellular space
  • Permeable cells for material exchange
  • Act as a barrier separating organs and systems