Basics in Human Anatomy Priya Ranganath, Suruchi Singhal, Leelavathy N, Vani Vijay Rao, Roopa R
Chapter Notes

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  • The term ‘anatomy’ is derived from a Greek word, ‘anatome’, meaning cutting up.
  • Anatomical position: Descriptive terms of position are used as though the body is standing upright with the upper limbs hanging by the sides and the palms of the hands directed forwards.
  • Sagittal plane—an imaginary plane passing through the median plane.
  • Parasagittal plane—an imaginary plane passing anteroposteriorly through any part of the body parallel to median plane.
  • Coronal plane—an imaginary plane passing at right angles to the median plane.
  • Superior or cephalic—part that is nearer to the head.
  • Inferior or caudal—part nearer the feet.
  • Anterior (ventral)—part nearer the front of the body.
  • Posterior (dorsal)—part nearer the back.
  • Median—part in the middle.
  • Medial—part nearer the median plane.
  • Lateral—part further away from median plane.
  • Superficial—part nearer the skin.2
  • Deep—part away from the skin.
  • Proximal—part nearer to the root of the limb.
  • Distal—part away from the root of the limb.
  • Movements of trunk along the sagittal plane are known as flexion (surfaces coming closer to each other) and extension (straightening or surfaces moving away from each other).
  • Movements of the trunk along the coronal plane are known as lateral flexion, in the limb they are called abduction (movements away from the median plane) and adduction (towards the median plane).
  • Rotation is the term applied to the movement in which a part of the body is turned around its own longitudinal axis.
Sagittal plane
Coronal plane
Longitudinal plane
Flexion, extension
Side to side (lateral flexion)
Flexion, extension
Adduction, abduction
Medial, lateral rotation
Adduction, abduction
Flexion, extension
  • The basic structural unit of all tissues and organs of the body are formed by the cells.
  • The shape of the cell differs in many ways. It may be flattened, cubical, columnar, fusiform, stellate, pyramidal or flask shaped.
  • Each cell consists of cell membrane (plasma membrane), nucleus and cytoplasm with organelles (Fig. 1.1).
  • It forms the outer boundary of the cell and separates it from adjacent cells and external environment.
  • It is a trilaminar membrane with two dense lamellae separated by a relatively clear layer.
  • It forms a covering for the cell structures and helps in various ways with the transport of substances into and out of the cell.
  • In some cells the surface area of the membrane may be greatly increased by the formation of microvilli, for absorption.
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    Fig. 1.1: Diagrammatic representation of a cell
  • Small invaginations of the cell membranes may become detached to lie free within the cytoplasm as pinocytic vesicles. By this method, material from outside can be taken into the cell.
  • It contains the genetic material, deoxyribonucleic acid (DNA) of the cell in the form of thin threads (chromatin) and one or more nucleoli embedded in a matrix of nucleoplasm.
  • The chromatin normally exists in two forms—condensed chromatin (heterochromatin) which represents the coiled segments of chromosomes and extended chromatin (euchromatin) where segments of the chromosome thread are uncoiled.
  • The nucleolus is seen as a dense region in the nucleus and contains ribonucleic acid (RNA).
  • The nuclear membrane is double layered, separated by the perinuclear space.
Endoplasmic Reticulum (ER)
  • It consists of a system of intercommunicating membranous sacs or channels and exists in two forms—rough endoplasmic reticulum which has ribosomes attached to the outer surface and smooth endoplasmic reticulum with no ribosomes.4
  • They are typically arranged in flattened parallel rows. It is prominent in cells that are manufacturing secretory substances.
  • Rough ER helps in protein synthesis and storage while smooth ER helps in lipid and steroid synthesis.
  • They appear as dense rounded granules lying singly or in dense clusters in the cytoplasm in the form of rosettes or spirals (polysomes) or may be attached to ER.
  • They are composed of ribonucleoproteins and are sites of protein synthesis.
Golgi Apparatus
  • This is a system of sacs arranged as stacks of coins and vesicles like endoplasmic reticulum but with no ribosomes attached to it.
  • It is also seen prominently in secretory cells.
  • They transfer materials synthesized by the ribosomes at the endoplasmic reticulum to the cell surface.
  • The part of the Golgi apparatus that contain newly manufactured material breaks away from the rest and pass towards the surface of the cell as secretion granules.
  • They are rod-like bodies bounded by a double layered membrane.
  • The outer membrane is smooth while the inner membrane is thrown into folds or cristae which project into the internal substance.
  • The mitochondria provide the metabolic energy for the cell by generating ATP.
  • These are dense granular structures bounded by membrane and containing hydrolytic enzymes.
  • Their function is to break down and digest material that has been brought into the cell by phagocytosis. The phagocytic vacuoles (phagosomes) fuse with lysosomes to enable the enzymes to act on the phagocytosed material.
  • They are present in many cells and help to maintain the cell shape.
  • The fibrils present in the muscle fibres are responsible for their contractility.
  • They become part of mitotic spindles in dividing cells.5
  • In the resting cells, if they are seen (as in processes of the nerve cells), they act as stabilizing elements.
  • These are a pair of short rod-shaped bodies found adjacent to the nucleus lying at right angles to each other.
  • During mitosis they undergo replication and then each pair moves to opposite poles of the nucleus where they take part in the formation of mitotic spindle.
  • Centrioles also give rise to cilia.
  • These are pigments like melanin or lipofuscin, storage granules such as glycogen and fat, and secretion granules.
  • Draw a diagram of cell and label the parts
  • Cell membrane—structure and functions
  • Nucleus—structure and functions
  • Mitochondria—structure and functions
  • Endoplasmic reticulum—structure and functions
  • Golgi apparatus—structure and functions