Structural Organisation in Animals - I PDF

Structural Organisation in Animals - I © 2022, Aakash BYJU'S. All rights reserved Key Takeaways Epithelial Tissue 1 Simple Compound 2 Connective Tissue Loose Nervous Tissue 3 Muscular Tissue 4 Dense Specialized Skeletal Fluid Summary © 2022, Aakash BYJU'S. All rights reserved Level of Organisation T...

Structural Organisation in Animals - I © 2022, Aakash BYJU'S. All rights reserved Key Takeaways Epithelial Tissue 1 Simple Compound 2 Connective Tissue Loose Nervous Tissue 3 Muscular Tissue 4 Dense Specialized Skeletal Fluid Summary © 2022, Aakash BYJU'S. All rights reserved Level of Organisation Tissue Organ Organ system A group of similar cells along with the intercellular substances that perform a specific function is known as tissue. A system of tissues that work together on a larger scale to do certain jobs is an organ. A group of organs that work together to perform common bodily functions is an organ system. Levels of organisation Organism Cell Cell is the fundamental unit of life. © 2022, Aakash BYJU'S. All rights reserved Organ systems come together to form a multicellular organism. An organism is a recognisable and self-contained individual. Animal Tissues Animals with tissue systems or a higher level of organisation are all made up of the four basic types of tissues. Epithelial tissue Connective tissue Nervous tissue Epithelial cells Epithelium Blood capillary Basement membrane © 2022, Aakash BYJU'S. All rights reserved Intercellular space Tissue on which the epithelium rests Nucleus Muscular tissue Epithelial Tissue It is commonly known as epithelium. It has a free surface. It is a large sheet of cells that forms the lining of all the body surfaces. Epithelial cells are arranged compactly with little intercellular spaces. These cells rest on a non-cellular basement membrane which is made up of ○ Basal lamina - upper thin layer ○ Reticular lamina - lower thick fibrous layer Generally, they are avascular and do not have blood vessels. © 2022, Aakash BYJU'S. All rights reserved Outside environment Fluids or free surface Epithelium Epithelium Basement membrane Basement membrane Other body tissue Other body tissue Epithelial Tissue Simple Single layer of cells Lining for body cavities, ducts, and tubes Example: Alveolar cells Compound Two or more layers of cells Protective function Example: Cheek cells Squamous Cuboidal Stratified Columnar Pseudostratified © 2022, Aakash BYJU'S. All rights reserved Transitional Simple Epithelial Tissue Squamous Cuboidal It is also known as pavement epithelium. It is the layer of thin flat cells with prominent nuclei. It appears cuboidal in vertical sections and polygonal from the surface. It has circular nuclei. It has flattened cells with irregular boundaries. It participates in secretion, absorption, and excretion. It forms the diffusion boundary. It occurs in the alveoli of lungs, lining of the blood, and lymph vessels. It lines small salivary and pancreatic ducts with thyroid follicles. Squamous cell Basement membrane © 2022, Aakash BYJU'S. All rights reserved Cuboidal in vertical section Basement membrane Simple Epithelial Tissue Cuboidal Cuboidal epithelium bears microvilli in absorptive regions on their free ends. They give a brush-border appearance and hence called brush-bordered epithelium. They are found in proximal tubules of kidney. Microvilli Cytoplasm Nucleus Mitochondrion © 2022, Aakash BYJU'S. All rights reserved Simple Epithelial Tissue Columnar Pseudostratified Appear column-like in vertical section. It is a single layer of columnar cells. Nucleus usually located near the base. Lines the stomach and the inner layer of small intestine. It appears to be double layered due to different sizes of cells. Nuclei are present on different levels. Increases surface area for absorption. Shorter cells lack cilia and secrete mucus. Longer cells are ciliated and propel the mucus and the particle towards the larynx. Nucleus Basement membrane Tall columnar cell Nuclei at different levels Basal cell © 2022, Aakash BYJU'S. All rights reserved Simple Epithelial Tissue Cuboidal and columnar epithelium can specialize into 2 distinct types, besides their normal form Ciliated Glandular Type of cuboidal or columnar epithelium bearing cilia Cuboidal or columnar cells Specialised for secretion Composed of a single layer of cube-like cells Commonly found in inner surface of hollow organs like bronchioles and fallopian tubes. Main functions is to move particles or mucus in a specific direction They can be ○ Unicellular: Consisting of isolated glandular cells - Goblet cells of alimentary canal ○ Multicellular: Consisting of cluster of cells - Salivary glands © 2022, Aakash BYJU'S. All rights reserved Types of Glands Types of glands Duct Exocrine Presence of ducts Secretes cell products like mucus, saliva, oil, milk, digestive enzymes Example: Salivary glands, mammary glands, sebaceous glands, etc. Endocrine Ductless Secretes hormones Example: Testes, pancreas, pituitary glands, ovaries, etc. © 2022, Aakash BYJU'S. All rights reserved Exocrine cell Secretory product Duct Blood flow Endocrine cell Hormone Blood vessel Cells pouring secretion into blood vessel Types of Glands Holocrine Product of secretion is shed with the whole cell leading to its destruction E.g. - Sebaceous glands Holocrine Disintegrating cell and its released contents Mitotic divisions to replace cells © 2022, Aakash BYJU'S. All rights reserved Apocrine Only the apical portion of the cytoplasm is discharged along with the secretory product E.g. - mammary glands Apocrine Pinched off apical portion of cell Merocrine Secretory cells leave the cell by exocytosis with no loss of other cellular material E.g. - the pancreas Merocrine Secretory product Intact cell Compound Epithelial Tissue This epithelial consists of more than one layer of cells. Only the deepest layer rests on the basement membrane. They provide protection to underlying tissues against mechanical, chemical, thermal or osmotic stresses. Types Stratified epithelial tissue ‘Stratum’ means layer. It consists of more than one layer of cells. It provides protection to underlying tissues under stress conditions. It is the deepest layer formed by columnar cells. The superficial cells can vary from squamous to cubicle. © 2022, Aakash BYJU'S. All rights reserved Transitional epithelial tissue The cells are thinner and more elastic when compared to stratified epithelium cells. 4-6 Layer of cells ○ ○ ○ Innermost layer of cells - cuboidal or columnar Middle layer of cells - pear-shaped Surface cells are large and oval-shaped Compound Epithelial Tissue Stratified epithelial tissue Stratified non-keratinised squamous epithelium covers moist surfaces like buccal cavity, pharynx and oesophagus. Stratified keratinised squamous epithelium covers the dry surface of skin. In keratinised epithelium, heavy deposits of keratin (insoluble protein) in the dead superficial cells makes the epithelium impervious to water. Transitional epithelial tissue It lines the surface of the urinary bladder and ureters. It allows considerable extension of these organs to accommodate urine. Normal Multicellular cell Basement membrane © 2022, Aakash BYJU'S. All rights reserved Stretched Large oval cells Intercellular Junctions Tight (Zonula occludens) Tight junctions stop substances from leaking across the tissue Adhering Adhering junctions cement neighboring cells together © 2022, Aakash BYJU'S. All rights reserved Gap junction facilitate cell communication by movement of ions and molecules between adjacent cells Plasma membranes of adjoining cells Interlocking junctional proteins Plasma membranes of adjoining cells Gap (Macula adherens) Plasma membranes of adjoining cells Channel between cells Connective Tissue They are the tissues that link and support different tissues and organs in the body. The characteristics of connective tissues are as follows: ○ They are the most abundant tissue of the body. ○ They are generally vascular. Secretion of connective tissues Structural proteins Modified polysaccharides Provide strength, elasticity, and flexibility Collagen Present in bones, muscles, tendons Collagen fibres of collagen are unbranched © 2022, Aakash BYJU'S. All rights reserved Accumulate between cells and structural proteins Act as a matrix or a ground substance Elastin Found in the skin Elastic in nature Elastin fibres are branched Connective Tissue Types of connective tissues Loose connective tissue Areolar Adipose Dense connective tissue Dense regular Tendon Ligament © 2022, Aakash BYJU'S. All rights reserved Dense irregular Specialised connective tissue Skeletal Fluid Bone Blood Cartilage Lymph Loose Connective Tissue It is a binding tissue that holds organs and other tissues together. It consists of loosely arranged cells and fibres. The components are embedded in a semifluid matrix. Adipose Areolar Macrophages Adipose tissue Fibroblasts Nucleus Plasma membrane Mast cell Layer of the skin © 2022, Aakash BYJU'S. All rights reserved Fat storage area Loose Connective Tissue Areolar Most widely distributed in animal body Present beneath the skin Joins skin to muscles Found around muscles, blood vessels and nerves Three types of cells: ○ Fibroblasts - principal cells, secrete major amount of matrix ○ Macrophages/Histiocytes phagocytic in nature ○ Mast cells/Mastocytes - irregularly ovoid cells containing basophilic granules which contain histamine, heparin and serotonin © 2022, Aakash BYJU'S. All rights reserved Adipose Contains large, spherical or oval cells called fat cells or adipocytes. ○ Cytoplasm and organelles in this are pressed by fat into a narrow annular layer just beneath plasma membrane Present beneath skin, around kidneys, mesentery and bone marrow Synthesises, stores and metabolises fat ○ Serves as fat reservoir, shock absorber and insulator Dense Connective Tissue The cells and fibres of the dense connective tissue are compactly arranged. Regular Irregular Collagen fibres are present in rows between many parallel bundles of fibres Fibroblasts and various types of fibres (mostly collagen) are oriented irregularly. They form the principal components of ligaments and tendons. ○ Tendons consist of parallel bundles of collagen fibres ○ Ligaments consist of collagen fibres arranged in bundles with fibroblasts present in rows between bundles along with elastin fibres. This tissue is present in the skin. © 2022, Aakash BYJU'S. All rights reserved Specialized Connective Tissue Skeletal connective tissue Cartilage Extracellular ground substance is solid Forms the endoskeleton of vertebrates which: ○ Supports the body ○ Protects various organs ○ Helps in locomotion Flexible connective tissue Keeps the motion of the joint fluid Helps in maintaining the smoothness in movements of the joints by coating the surfaces of the bones in our joints and by cushioning bones against impact. In vertebrates, most cartilages in the embryo stage are replaced by bones in the adult stages © 2022, Aakash BYJU'S. All rights reserved Bone Hard and non-pliable connective tissue Ground substance is made up of calcium salts and collagen fibres 70% inorganic matter, 30% organic matter Decalcifies in HCL, unaffected in KOH Skeletal Connective Tissue Cartilage Structure Location Matrix - solid, pliable, resists compression ○ Produced and maintained by cartilage cells Nasal septum Epiglottis Fluid filled spaces called lacunae are present Tip of nose Contain cartilage-forming cells called chondrocytes Outer ear joints Between adjacent bones of the vertebral column Limbs and hands in adults Function Provides support and flexibility to body parts Resists compression Smoothens surface at joints ○ Hence, prevents wear and tear of bones due to friction © 2022, Aakash BYJU'S. All rights reserved Skeletal Connective Tissue Bone Structure Function Matrix - very hard and non pliable ○ Due to presence of calcium phosphate, calcium carbonate and salts like ossein and collagen fibres ○ Arranged in form of layers called lamellae Ring shaped fluid filled spaces called lacunae present in them. Lacunae contains osteocytes Long bones have bone marrow cavity ○ Filled with soft and semisolid fatty tissue - bone marrow Site of production of blood cells Location © 2022, Aakash BYJU'S. All rights reserved Provides structural framework to body Supports and protects tissues and organs such as brain, lungs etc. Provides surface for attachment of muscles Helps in locomotion and movement Storage site of calcium and phosphate Endoskeleton of adults vertebrates Skeletal Connective Tissue Bone Compact It forms the dense outer layer of the bones. It is composed of many longitudinal, column-like structures called Haversian systems. ○ Several concentric layers (lamellae) of bony matrix encircle a longitudinal central Haversian canal. Haversian canals are connected by Volkmann canals. Marrow cavity of long bones contain fatty yellow bone marrow in adults. © 2022, Aakash BYJU'S. All rights reserved Spongy Open lattice of bone present at the ends of the long bone (epiphysis) ○ Hence, also called cancellous bones Contains red bone marrow where blood cells are formed Consists of a network of many fine irregular bony plates or trabeculae Skeletal Connective Tissue Types of bones Membrane bones Cartilage bones Also called endochondral or replacing bones Formed by replacement of cartilage by the bone Chondroclasts dissolve cartilage for replacement E.g. - Humerus, femur, vertebrae, ribs © 2022, Aakash BYJU'S. All rights reserved Also called dermal or investing bone Formed in dermis of the skin E.g. - skull bones, clavicle Sesamoid bones Formed by the ossification of the tendons E.g. - patella Visceral bones Formed in visceral/soft organs in some species of animals E.g. - os cordis, os falciparum, os penis Fluid Connective Tissue Made of ○ fibre free fluid matrix ○ specialised living cells Can’t divide or secrete matrix Help in transportation of nutritive elements, gases, excretory products, hormones Types of fluid connective tissue Blood © 2022, Aakash BYJU'S. All rights reserved Lymph Fluid Connective Tissue WBCs/Leukocytes Rounded or irregular in shape Able to change shape and amoeboid movement Capable of diapedesis RBCs Components of blood Oval shaped, biconcave, nucleated in most vertebrates In mammals, they are circular, biconcave, disc-like and lack nuclei Platelets Also called thrombocytes Minute, non-nucleated, round or biconvex Plasma © 2022, Aakash BYJU'S. All rights reserved Nervous Tissue Develops from the ectodermal tissue. Controls all body activities Conducts nerve impulses from one part to another part of the body Coordinates various body parts and functions Forms brain, spinal and nerves Types of nervous tissue Neurons Neuroglial tissue Neuroglial cells provide support cells around brain, spinal cord, and ganglions They are also known as nerve cells Glia = glue Ganglions are group of neurons Also known glial cells Neurons are linked together Basic structural and functional unit of neural tissue is neuron Excitable cells © 2022, Aakash BYJU'S. All rights reserved Nervous Tissue Parts of neurons Cyton/Cell body Dendrites Axon Consists of a central nucleus and cytoplasm Short and branched processes arising from the cyton Single cylindrical projection emerging from cyton Contains characteristic Nissl’s granules which stain deeply Carry impulses towards cyton They are large, irregular masses of ribosomes and RER © 2022, Aakash BYJU'S. All rights reserved Synapse Axon ends in axon ending (terminal arborizations) Axon terminal is very closely placed to the dendrite of the other neuron to transfer impulses Carries message away from cyton This zone is called synapse Neurotransmitters transfer signal at synapse Surrounded by a sheath (Neurilemma) of neuroglial cells called myelin sheath Myelin sheath is interrupted at nodes of ranvier Nervous Tissue Diagram of a neuron Dendrites Nucleus Axon Axon terminal Nodes of Ranvier Synaptic knob Schwann cells Cell body © 2022, Aakash BYJU'S. All rights reserved Myelin sheath Nervous Tissue Types of neurons Unipolar One axon/dendrite Found in early embryos © 2022, Aakash BYJU'S. All rights reserved Bipolar Multipolar One axon and one dendrite One long axon and multiple dendrites Found in olfactory epithelium and retina of eye Very common Found in brain and spinal cord Pseudounipolar Apolar Bipolar but Primitive appear unipolar neurons which first appeared Single process in cnidarians divides into dendrite and axon Found in dorsal root ganglion of the spinal nerve Undefined polarity Nervous Tissue Types of glial cells Large in size with number of protoplasmic processes Form maximum number of glial cells Help in nervous tissue repair Form blood-brain barrier © 2022, Aakash BYJU'S. All rights reserved Schwann cells Oligodendrocytes Astrocytes Form an insulating layer called myelin sheath around axon of neurons in CNS Have few protoplasmic processes Microglial cells Form an insulating layer called myelin sheath around axon of neurons in PNS Mesodermal in origin Small in size Featheryprocesses Lipid rich layer Help in phagocytosis Muscular Tissue Made up of long, cylindrical fibres arranged in a parallel fashion Muscle fibres consist of fine fibrils known as myofibrils Aid and control movements Contract and relax to generate movement in response to stimulus Types of muscle tissues Skeletal muscle tissue Closely attached to the skeletal bones Muscle fibres are striated Fibres are bundled together in a parallel fashion Sheath of tough connective tissue encloses several bundles of muscle fibre Multinucleated, voluntary in nature Found between bones © 2022, Aakash BYJU'S. All rights reserved Muscular Tissue Smooth muscle tissue Striations are absent Fibres tapers at both ends (fusiform shape) Cell junction holds cell together Fibres are bundled together in connective sheath Uninucleated, involuntary in nature Found in stomach, intestine, uterus, etc. © 2022, Aakash BYJU'S. All rights reserved Muscular Tissue Cardiac muscle tissue Contractile tissue Present only in the heart Cell junctions cause the fusion of plasma membrane of adjacent cells At some places, intercalated discs (communicated junctions) are formed at the fusion points Allows the cells to function in a coordinated manner Unstriated, uninucleated and involuntary © 2022, Aakash BYJU'S. All rights reserved Summary Epithelial tissue Simple Single layer of cells Lining for body cavities, ducts, and tubes Example: Alveolar cells Two or more layers of cells Protective function Example: Cheek cells Squamous Stratified Cuboidal Transitional Columnar Pseudostratified © 2022, Aakash BYJU'S. All rights reserved Compound Summary Types of glands Exocrine Presence of ducts Secretes cell products like mucus, saliva, oil, milk, digestive enzymes Example: Salivary glands, mammary glands, sebaceous glands, etc. Intercellular junctions Tight (Zonula occludens) Adhering Endocrine Ductless Secretes hormones Example: Testes, pancreas, pituitary glands, ovaries, etc. © 2022, Aakash BYJU'S. All rights reserved Gap (Macula adherens) Summary Types of connective tissues Loose connective tissue (Loosely arranged) Dense connective tissue (Compactly arranged) Specialised connective tissue Areolar Tissue (Supports framework for epithelium) Regular tissue (Parallel bundled) Cartilage (Flexible connective tissue) Adipose Tissue (Helps in storage of fat) © 2022, Aakash BYJU'S. All rights reserved Irregular tissue (Oriented irregularly, found in skin) Bone (Hard and non-pliable) Blood (Fluid connective tissue) Summary Bone Cartilage Composed of tough inflexible material called ossein Composed of firm but flexible material called chondrin Matrix occurs in concentric lamellae Matrix occurs in homogeneous mass Osteoblasts produce new osteocytes Chondroblasts produce new chondrocytes Osteocytes are present in the lacunae Chondrocytes are present in the lacunae Provides support and flexibility to body parts Provides structural framework to body and protection to organs © 2022, Aakash BYJU'S. All rights reserved Summary Dendrites Neural tissue Neurons Parts Cyton Axon Basic structural and functional unit of neural tissue is neuron Synaptic knob Astrocytes Neuroglial cells Glial cells provide support cells around brain, spinal cord, and ganglions © 2022, Aakash BYJU'S. All rights reserved Types Schwann cells Oligodendrocyte Microglia Summary Skeletal muscle Smooth muscle Cardiac muscle Occur in the limbs, body wall, face, neck etc. Occurs in the posterior part of oesophagus, urogenital tract, iris etc Occurs in the walls of heart Cylindrical in shape Spindle shaped Cylindrical in shape Multinucleated Uninucleated Uninucleated Voluntary in nature Involuntary in nature Involuntary in nature Intercalated discs are absent Intercalated discs are absent Intercalated discs are present Striated Unstriated Unstriated © 2022, Aakash BYJU'S. All rights reserved