AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

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AP Inter 1st Year Zoology Notes 2nd Lesson Structural Organisation in Animals

→ The study of tissues is known as histology or microanatomy.

→ In the evolution of animals, the major event of significance is the development of tissues.

→ A group of cells having same origin, same structure and performing same function is called ’tissue’.

→ As somebody rightly observed Tissues are jacks of all trades and masters of none.

→ Arrangement of body parts in geometrical design is termed as symmetry.

→ Concentration of nerve and sensory cells at the anterior end of the organism is called caphalization.

→ Bilaterally symmetrical animals are more efficient than the other animals.

→ If a body does not exhibit any particular geometrical design, the animal is said to be asymmetrical.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Tissues are essentially of four types – epithelial, connective, muscular and nervous.

→ The term ‘coelom’ was coined by Hackel.

→ The body cavity, which is lined by mesoderm is called Coelom.

→ Based on major taxonomic groups called Acoelomata, Pseudocoelomata and Eucoelomata.

→ Flatwarms are included in the taxon Acoelomata.

→ Eucoelomates are further divided into a) Schizocoelomates – Annelida, Arthropoda, Mollusca, b) Enterocoelomates – Echinodermata, Chordata.

→ The types of animals tissues broadly recognized are 1) Epithelical tissue, 2) Connective tissue, 3) Muscular tissue, 4) Nervous tissues.

→ Connective tissue is formed by cells and extra cellular matrix. Matrix consists of fibres and ground substance.

→ BAT generates considerable heat and maintains body temperature in the newborn.

→ Appositional growth of cartilage results form the differentiation of perichondrial cells.

→ The refractive index of the collagen fibrils of hyaline cartilage is almost the same as that of the ground substance.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ In adults, long bone does not grow in length as the epiphyseal plate disappears leaving a bony epiphyseal cell.

→ Bone has grow in the thickness only by appositional growth resulting from the differentiation of periosteal cell.

→ Fall in the level of albumin in blood plasma results in oedema.

→ The biconcave shape provides a large surface-to-volume ratio to the mammalian erythrocyte.

→ Agranulocytes lack specific granules but possess azurophilic granules.

→ The interstitial fluid that passes into the lymphatic vessels is called lymph.

→ Muscles contact and relax, but do not expand.

→ Gap junctions in intercalated discs of cardiac muscle provide ionic continuity between adjacent cells.

→ Myelin sheath around axons is produced in the CNS by oligodendrocytes and in the PNS by Schwann cell.

→ Supporting cells are absent around the Un-myelinated axon on the CNS but presenting PNS.

→ In the CNS grey appearance of grey matter of is due to Nissil bodies whereas the white appearance of white matter is due to myelin.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Aggregations of neuronal cell bodies are called ganglia in PNS and nuclei in CNS.

→ Bundles of nerve fibres from nerves in PNS and tracts in CNS.

→ Cranial nerves and spinal nerves contain myelinated fibres whereas autonomic nerves contain un-myelinated fibres.

→ Anticoagulants : These are the substances that prevent the coagulation of blood, when blood flows through blood vessels, e.g. heparin

→ Articular cartilage : It is the cartilage found at the free surfaces of long bones that forms Joints.

→ Blubber : It is the thick, fatty layer that lies underneath the skin of whales and other aquatic mammals. It helps in thermal insulation.

→ Central axis : An imaginary straight line joining the mid point at one end or surface and the midpoint at the opposite end or surface. It is also called the principal axis.

→ Diapedesis : The passage of leucocytes of blood into the matrix of connective tissues through the walls of capillaries by an amoeboid movement.

→ Endothelium : The simple squamous epithelium that lines the inner surface of blood vessels and heart.

→ Epiphyses : These are the expanded ends of long bones, which are made of spongy bone.

→ Frontal plane : The plane that runs along the anterior – posterior and transverse axes.

→ Haemocoel : The functional perivisceral cavity, that lies around the visceral organs of arthropods and molluscs which is filled with the blood (haemolymph).

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Haversian canal : These are the elongated canals that run parallel to the marrow cavity of compact bones of mammals. They contain blood vessels, lymphatic vessels and nerves.

→ Hydrostatic skeleton : In pseudo-coelomates and eucoelomates, the body cavity is filled with a fluid which gives proper shape to the body as an endoskbleton does.

→ Ligament : A dense fibrous tissue strand, which connects bones to other bones in general. Extensive pulling of ligament causes sprain.

→ Median sagittal plane : The plane that runs along the anterior, posterior and sagittal axes.

→ Megakaryocytes : Giant cells of red bone marrow that produce blood platelets by fragmentation.

→ Muscle fatigue : It is the inability of the muscle to undergo further contraction due to the accumulation of lactic acid formed during anaerobic respiration, because of rapid exercise.

→ Oedema : It is an abnormal accumulation of interstitial fluid beneath the skin or in one or more cavities. Fall in the levels of plasma proteins mainly serum albumin causes a decrease in the osmotic pressure of blood.

→ Osteoblasts : These are the immature cells that secrete organic matter of the matrix of a growing bone. Immature osteoblasts become mature cells, the osteocytes, in the adult stage.

→ Perivisceral cavity : It is the cavity that encloses visceral organs. The perivisceral cavity of nematodes is pseudocoelom, that of annelids is eucoelom.

→ Plane : The flat area that runs through any axis.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Polycythemia : It is an abnormal rise in the RBC count. The people who live at the higher altitudes generally show polycythemia due to low partial pressure of oxygen at the higher altitudes.

→ Primary induction : It is a kind of interaction between tissues of different origin involved in the development of specialized tissues.

→ Reticular cells : These are the specialized fibroblasts that secrete reticular fibres of matrix. Reticular lamina : It is a part of the basement membrane of the epithelium that lies close to the underlying tissues.

→ Retroperitoneal organs : Organs that are located in between the dorsal body wall and parietal layer of peritoneum. E.g. kidneys

→ Sagittal axis : An imaginary straight line that joins mid dorsal and mid ventral ends.

→ Secondary bodycavity : True coelom of eucoelomates is called secondary body cavity, because it is formed by the replacement of primary body cavity, the blastocoel.

→ Spasms : These are sudden sustained involuntary contractions of smooth muscles of visceral organs.

→ Stereocilia : These are non-motile cilia-mechno sensing organelles in internal ear, epididymis etc., respond to fluid motion in numerous types of animals for various functions.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Synaptic knobs : These are bulb-like structures formed distally by the axon terminals and contain synaptic vesicles which have neuro-transmitters.

→ Transverse plane : The plane that runs through the sagittal axis and transverse axis.

→ Vasodilator : These are substances like histamine and bradykinin which increase the capillary permeability and cause inflammation in response to Infection or injury.

→ Structural organisation deals with structures, functions and types of cells, tissues of animals.

→ Development of tissues is a maj or event in evolution.

→ Animal tissues are four types: (i) Epithelial (ii) Connective (iii) Muscular (iv) Nerve tissue.

→ Epithelial tissue helps in secretion, protection, transport etc.,

→ Connective tissue binds and supports other tissues and organs.

→ Muscular tissue helps.in various type of movements both voluntary and involuntary.

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Nerve tissue brings coordination of various organs and helps in survival of organism.

→ Cephalization is the formation of nerve and sensory cells at the anterior part of the body.

→ ‘Tube-within-a-tube’organisation is first formed in fematoda. [IPE]

→ The organs like kidneys in vertebrates are covered by the parietal peritoneum only on the ventral side. The organs lined by it are called retroperitoneal organs. [IPE]

→ Mast cells secrete heparin, histamine, bradykinin and serotonin.

→ Tendons connect skeletal muscles to the bone. [IPE]

→ Ligaments connect one bone with another bone. [IPE]

→ ‘Fibrous cartilage’ is the strongest cartilage. [IPE]

→ Haversian system is a unit of compact bone. It consists of (i) Haversian canal (ii)Concentric bone lamellae (iii) lacunae (iv) canaliculi (v) Volkman’s canals.

→ Osteon: In a dense bone, a Haversian canal and the surrounding lamellae and lacunae are collectively called Osteon (Haversian system). [IPE]

→ Sesamoid bone is a tendon bone. It is formed by ossification in tendon. Ex: Patella (knee cap)

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ The percentage of volume of RBC in total volume of blood is Haematocrit value.

→ Cardiac muscle is the heart muscle (myocardium). [IPE]

→ Cardiac muscle is highly resistant to fatigue because it has numerous sarcosomes, many molecules of myoglobin and rich supply of blood for continuous aerobic respiration.

→ The muscles which are attached to skeletal structures are called skeletal muscles. [IPE] Skeletal muscles are attached to bones by tendons.

→ Frog’s heart when taken out of the body continues to beat for sometime, because Heart is ‘myogenic’ in nature, Heart is autoexcitable. [NEET-2017]

→ The function of the gap junction is to stop substance from leaking across a tissue. [NEET-2015]

AP Inter 1st Year Zoology Notes Chapter 2 Structural Organisation in Animals

→ Goblet cells of alimentary canal are modified from columnar epithelial cells. [NEET-2020]

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