Cell Types (Plant/Animal Tissue) PDF

Cell Types (Plant /Animal Tissue) Unlike unicellular microbes, animals and plants show a higher level of organization. They have complex body structure where a group of cells performs functions in a systematic way. In animals and plants, cells are groupe...

Cell Types (Plant /Animal Tissue) Unlike unicellular microbes, animals and plants show a higher level of organization. They have complex body structure where a group of cells performs functions in a systematic way. In animals and plants, cells are grouped together to form tissues. These tissues vary in their structure, function, and origin. Histology – Study of tissues Hierarchy of Biological Organization The biological levels of organization of living things arranged from the simplest to most complex Animal Tissues Types of Animal Tissue  EPITHELIAL TISSUES All layers and organs in the body are lined by a group of tissues called epithelial tissues which are commonly referred to as epithelium. They cover the surface of all internal as well as external organs.They line body cavities and hollow organs, and are the major tissue in glands. Epithelial tissue is highly permeable. Thus, it plays a significant role in the exchange of substances across the cells and helps in maintaining the osmoregulation. Depending on the number of layers of cells it is composed of, the epithelium has been divided into the simple epithelium and compound epithelium. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception. Epithelial tissue can have one or a combination of the following several functions: Protection: Epithelial tissue protects several aspects of your body. For example, your skin is made up of epithelial tissue and protects the tissues deeper in your body, such as blood vessels, muscle and internal organs. The cilia on the epithelial cells that line your intestines protect the rest of your body from intestinal bacteria. Secretion: Epithelial tissue in your glands (glandular epithelium) can secrete (release) enzymes, hormones and fluids. Absorption: The epithelial lining of your internal organs, such as your liver and lungs, can allow the absorption of certain substances. For example, the internal epithelial lining of your intestines absorbs nutrients from the food you eat. Excretion: Excretion is the removal of waste from your body. The epithelial tissue in your kidneys excrete waste, and the epithelial tissue in your sweat glands excrete sweat. Filtration: The epithelium of your respiratory tract filters out dirt and particles and cleans the air that you breathe in. Epithelial tissue in your kidneys filters your blood. Diffusion: In biology, diffusion is the passive movement of molecules or particles from regions of higher concentrations to regions of lower concentration. Simple squamous epithelial cells form a membrane that allows selective diffusion of materials to pass through. Diffusion helps with filtration, absorption and secretion functions. Sensory reception: Sensory nerve endings that are embedded in epithelial tissue allow your body to receive outside sensory stimuli. As an example, the stereo cilia on the surface of the epithelial tissue in your ear are essential for hearing and balance. In addition, your taste buds are embedded in the stratified squamous epithelium of your tongue. Types of Epithelial Tissues Location Function Simple Squamous Epithelium Air sacs of lungs and the lining of the Allows materials to pass through by heart, blood vessels, lymphatic diffusion and filtration, and secretes vessels lubricating substance. This type of epithelium typically regulates the passage of substances into the underlying tissue. Simple Cuboidal Epithelium In ducts and secretory portions of Secretes and absorbs small glands and in kidney tubules Simple Columnar Epithelium Ciliated tissues are in bronchi, Absorbs; it also secretes mucous uterine tubes and uterus; smooth and enzymes (non-ciliated tissues) are in the digestive tract, bladder -These cells line your stomach and intestines. - It helps in the directional movement of materials along with the hollow organs like the respiratory tract. The cuboidal or columnar epithelia which are specialized in secretions are called glandular epithelium which includes the exocrine and endocrine glands. Pseudostratified Columnar Epithelium Ciliated tissues lines the trachea and Secretes mucous; ciliated tissue much of the upper respiratory tract moves mucus Stratified Squamous Epithelium Lines the esophagus, mouth, and Being tightly packed, tight junctions vagina serve as barriers for pathogens, -Outer layer of skin (epidermis) mechanical injuries, and fluid loss. This type of epithelium usually has protective functions, including protection against microorganisms from invading underlying tissue and/or protection against water loss. The outer layer of your skin (the epidermis) is made of stratified squamous epithelial cells. Stratified Cuboidal Epithelium This type of epithelium is not as Protective tissue common and is found in the excretory ducts of your salivary and sweat glands. The male urethra and the ducts of Secretes and protects Stratified Columnar Epithelium some glands Rare type of epithelium and is seen in the mucous membrane (conjunctiva) lining your eyelids Epithelial Cell based on Specialized Functions  Lines the bladder, urethra and the (also known as urothelium) is made Transitional Epithelium ureters up of several layers of cells that become flattened when stretched. It lines most of your urinary tract and allows your bladder to expand. Glandular Epithelium Glands This type of epithelium is specialized to produce and secrete (release) substances. It’s found in your glands, which are specialized organs that can make, store and/or release substances such as hormones, proteins and water. Olfactory Epithelium Nasal cavity The olfactory epithelium, located within your nasal cavity, contains olfactory receptor cells, which have specialized cilia extensions. The cilia trap odor molecules you breathe in as they pass across the epithelial surface. Information about the molecules is then transmitted from the receptors to the olfactory bulb in your brain, where your brain then interprets the smell. CONNECTIVE TISSUE They connect and support the different tissues, organs, and parts of the body. Among the animal tissues, connective tissues are the most abundant ones in the body. The connective tissue cells are freely arranged in a matrix and are widely distributed in the body. Areolar Tissue a loose connective tissue that can be seen between the skin and muscles; in the bone marrow as well as around the blood vessels and nerves. The areolar tissue fills the spaces between the different organs and connects the skin to the underlying muscles. And therefore, it provides support to the internal organs as well as help in the repair of tissues.  Adipose Tissue (Fat) It is present in skin and organs. The areolar tissue consists of many types of fibres and cells. Among the cells are the adipocytes. These adipocyte cells together make the adipose tissue or the fat tissue. It is in these cells that fat is stored in the form of fat globules. Due to the storage of fat, the adipose tissue acts as an insulator. Blood Blood is a fluid connective tissue. It consists of a liquid matrix called the plasma, in which blood cells are present. So it can be said blood is an important lifeline. It travels all around the body in specialized blood vessels. Blood has many functions to play in the body. Primarily, it helps in the transport of gases, nutrients, hormones as well as the elimination of the waste materials. There are three types of blood cells that are found in the plasma. They are the Red blood cells (RBC) or Erythrocytes; White blood cells or Leucocytes (WBC) and Thrombocytes or Blood Platelets. The RBCs and the WBC’s are the living components of the blood. The RBCs have a pigment called hemoglobin, due to which blood appears red in colour. The WBCs help in protecting the body by attacking any foreign body that enters into the body, while the blood platelets are responsible for clotting of blood. Bone Bone is a hard connective tissue which forms the framework of the body. It has a rigid matrix rich in calcium and collagen fibers. Functions include protection, support, facilitates movements and serves as a site for blood cell production. Cartilage Cartilage is another type of connective tissue that has a solid matrix. It contains proteins and sugars. The cartilage tissue has widely spaced cells. Cartilage is also an important connective tissue as it helps in smoothening the bone surfaces at the joints. Cartilage is also present in the trachea, nose, ears, and larynx. Chondrocytes are the cells responsible for cartilage formation, and they are crucial for the process of endochondral ossification, which is useful for bone development.  MUSCLE TISSUE These tissues are composed of long cells called muscle fibers that allow the body to move voluntary or involuntary. Movement of muscles is a response to signals coming from nerve cells. In vertebrates, these muscles can be categorized into the following: These tissues are composed of long cells called muscle fibers that allow the body to move voluntary or involuntary. Movement of muscles is a response to signals coming from nerve cells. In vertebrates, these muscles can be categorized into the following: Smooth—not striated; involuntary These help in peristalsis and other involuntary functions of the body. Skeletal—striated; voluntary movements Provide support, help in movement and maintain homeostasis Cardiac—striated with intercalated disk for synchronized heart contraction; involuntary It helps in blood circulation and keeps the heart pumping NERVOUS TISSUE Nervous tissue makes up the peripheral and the central nervous system. It develops from the ectoderm of the embryo. It possesses the ability to initiate and transmit the nerve impulse. Its main components include: These tissues are composed of nerve cells called neurons and glial cells that function as support cells. These neurons sense stimuli and transmit electrical signals throughout the animal body. Neurons connect to other neurons to send signals. The dendrite is the part of the neuron that receives impulses from other neurons while the axon is the part where the impulse is transmitted to other neurons. Neurons – These are the structural and functional unit of nervous system. It comprises an axon, cell body and dendrites. Neuroglia – These are special cells found in the brain and spinal cord. They provide support to the neurons and fibres. Neurosecretory Cells – These function as endocrine organs. They release chemical from the axons direcly into blood.  PLANT TISSUES Plant tissues are groups of cells that are similar in their origin and their structure and perform similar functions. They are a collection of similar cells that perform organized functions for their plants. They are specialized for a unique purpose, and they can be combined with other tissues creating organs like flowers, stems, leaves, roots, etc. There are also different types of tissues, including meristematic and permanent tissues. MERISTEMATIC TISSUES These tissues can divide and re-divide, forming new cells through the process of mitotic cell division. These newly formed cells will be similar to the parent cells, but they start to differentiate when they grow, and their characteristics keep changing. They assist in the major growth of the vegetation through growth in length and diameter. The cells of meristematic tissues have a thin primary cell wall made up of cellulose. Each cell also has a dense cytoplasm and a nucleus with few vacuoles. They are generally oval, rectangular, or polygonal in shapes. APICAL These occur at the growing tips and apicals of roots and stems. They raise the length of the plant. INTERCALARY They occur at the internodes and basis of leaves. They raise the size of the internode. LATERAL These occur in the radial parts of the stems and roots. They increase the thickness of plants. PERMANENT TISSUES These are a group of living or dead cells usually formed by the meristematic tissues. They generally lose their ability to divide, thus becoming permanent tissues. They are matured meristematic cells. As they have lost their ability to divide, they take up permanent shares, sizes, places, etc. This process of taking up the permanent shape, size, etc., is called cellular differentiation. There are two types of permanent tissues: simple permanent tissues and complex permanent tissues.  Simple Permanent Tissues These tissues are composed of thin-walled cells having large vacuoles. The cells are loosely packed, and intercellular spaces are quite evident in these types of cells. They are generally isodiametric in shape. These tissues provide support to the plants and stores food. They are found in non-woody and soft parts of stems, roots, flowers, fruits, etc. They are elongated living cells with minute little intercellular gaps. Their cell walls are made up of pectin and cellulose. They provide flexibility with structural frameworks and also mechanical support to the plants. They are found in the marginal sections of the stems and leaves. They are long, narrow, and thick-walled because of lignin deposition in their cell wall. They do not have any intercellular gap. Their main function is to provide strength to the plants. They are generally found in the veins of leaves, vascular tissues of stems, etc.  Complex Permanent Tissues These tissues are made up of more than one type of cell with a common origin and work together to perform similar functions. They help transport mineral nutrients, organic food material solutes, water, etc. Hence, they are also known as conducting and vascular tissues. These are divided into 2 types of tissues, they are: Xylem: This tissue helps to transport all dissolved substances and water throughout the plant. It is also called the chief conducting tissue. These tissues are organized in a tubular fashion throughout the main axis of stems and roots. The various components of the xylem included: vessels, tracheids, xylem fibers, parenchyma, etc. Most of the conduction here is vertical, but lateral conduction occurs through the rays, which are horizontal rows of long parenchyma cells. Protective Tissues The last type of plant tissue is protective tissues, and they provide support and fortification to plants. There are 2 types, cork and epidermis. Cork: It is an external type of protective tissue. These cells are lifeless and lack intercellular gaps. The walls of the cells are coagulated with suberin. The main function of suberin is it makes the plant impervious to gas and other water molecules. Epidermis: This is a cell made up of an outer casing throughout the structure of the plants. The stomata merge with this layer at certain places. CELL MODIFICATIONS What is Cell Modification? These are specialized cell structures or modifications re-acquired by the cell after cell division that helps the cell in different ways It is an actual process that occurs after cell division where the newly-formed cells are structurally modified so that they can perform their function efficiently and effectively. APICAL MODIFICATIONS  Cell modification found on the apical surface of the cell.  It is specialized to carry out functions that occur at these interfaces, including secretion, absorption, and movement of luminal contents. Cilia and Flagella  Cilia are projections, usually short, hair like structures and a type of organelle seen on the apical surface of epithelial cells. This assists in the movement of material over the epithelial surface in a manner parallel with the surface of the epithelium  Flagella are long, whip-like structure that are formed by microtubules protruding from the cell body of bacteria and some eukaryotic cells.  In humans, flagella and cilia are important in reproduction. Sperm have flagella to enable them to swim. It uses its flagellum to swim to reach the egg. In females, the cilia in the fallopian tube help move the egg or embryo toward the uterus Villi and microvilli  Villi are finger-like projections that arise from the epithelial layer in some organs.  They help to increase surface area, allowing faster and more efficient absorption.  Microvilli are smaller projections than villi which functions primarily on the efficient absorption of molecules Pseudopods  Temporary, irregular lobes formed by amoebas and some other eukaryotic cells. It bulges outward to move the cell or engulf the prey.  It primarily consist of actin filaments and may also contain microtubules and intermediate filaments.  Pseudopods are used for motility and ingestion. Extra Cellular Matrix (ECM) Most animal cells release materials into the extracellular space, creating a complex meshwork of proteins and carbohydrates called ECM. A major component of the extracellular matrix is the protein collagen. Collagen proteins are modified with carbohydrates, and once they're released from the cell, they assemble into long fibers called collagen fibrils In the extracellular matrix, collagen fibers are interwoven with a class of carbohydrate-bearing proteoglycans, which may be attached to a long polysaccharide backbone. The extracellular matrix also contains many other types of proteins and carbohydrates. BASAL MODIFICATIONS Cell modification found on the basal surface of the cell basement membrane.  Hemidesmosomes  These allow for strong attachment between cells or to a basement membrane.  Desmosomes attach to the microfilaments of cytoskeleton made up of keratin protein.  Hemidesmosomes are similar to desmosomes in terms of function, however, they attach the epithelial cell to the basement membrane rather than the adjacent cell. LATERAL MODIFICATION  Cell modification found on the sideways of the cell.  These are tight junctions, adhering junctions and gap junctions.  These structures consist of protein complexes and induce connectivity between adjacent epithelial cells, between cell and ECM.  They can contribute to the barrier function of epithelia and control the paracellular transport  Tight Junctions  also called zonula occludens or occluding junctions) are a type of cell junction characterized by forming an adhesion complex between two neighboring cells serving as a tight seal between the cells.  Being tightly packed, tight junctions serve as barriers for pathogens, mechanical injuries, and fluid loss. Adherens Junctions  Protein complexes that occur in cell to cell junctions in epithelial and endothelial tissues, usually more basal than tight junctions. It fastens cell to one another. Gap Junctions  It is also known as communicating junctions  These are specialized intercellular connections between multitude of animal cell-types.  They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells