# Anatomy and Physiology of Animals/Glossary/M-N

A-B | C-D | E-F | G-H | I-J | K-L | M-N | O-P | Q,R,S | T,U,V,W,X,Y,Z
| Word | Meaning |
| M | |
| Macrophage | A large phagocytic cell present in many tissues |
| Mammary gland | The milk producing gland |
| Mandible | The bone of the lower jaw |
| Marrow | The soft sponge like material in the cavities of bone |
| Matrix | The substance of a tissue in which the more specialised structures are embedded |
| Maxilla | The bone of the upper jaw |
| Medial | Towards the midline |
| Mediastinum | The tissue that separates the two sides of the lung |
| Medulla | Inner part of an organ |
| Medulla oblongata | The part of the brain stem or hind brain |
| Meiosis | The type of cell division for production of gametes. Halves the number of chromosomes |
| Melanin | The dark pigment in the skin and hair |
| Melatonin | The hormone produced by the pineal gland |
| Membrane | A thin, flexible sheet of tissue |
| Meninges | The membranes covering the brain and spinal cord |
| Mesentery | The membrane attaching the small intestine to the abdominal wall |
| Metacarpals | The bones of the “hand” |
| Metastasis | The distant spread of disease especially a malignant tumour from its site of origin |
| Metatarsals | The five bones of the foot that connect the “ankle” to the toes |
| Microfilaments | A solid contracting strand in the cytoplasm of cells that brings about cell contraction. |
| Microtubule | A hollow rod of protein in the cytoplasm of all eukaryotic cells and in cilia, flagella, and the cytoskeleton |
| Microvilli | The microscopic fingerlike projections from the membrane of the cells covering the villi of the small intestine |
| Middle ear | The cavity in the skull between the eardrum and inner ear housing the auditory ossicles |
| Milk teeth | The first set of teeth in a young animal |
| Minute volume | The volume of air inspired or expired during a minute of normal tidal breathing |
| Mitochondrion | The organelle in cell cytoplasm that produces energy |
| Mitosis | The cell division for growth and repair. Produces 2 cells identical to parent and each other |
| Molars | The more posterior cheek teeth |
| Monocyte | The largest leukocyte. It is phagocytic and has no granules in the cytoplasm |
| Monosaccharide | The simplest carbohydrate. Also known as simple sugar |
| Morula | The solid mass of cells produced by successive divisions of the fertilized ovum |
| Mucus | A thick fluid secretion |
| Myelin | The fatty insulating coating to an axon of a neuron |
| N | |
| Nasal cavity | The space just inside the nostril |
| Negative feedback | Control in which the stimulus initiates actions that reverse or reduce the stimulus |
| Nephron | The functional unit of the kidney |
| Nerve | A bundle of nerve fibres |
| Nerve impulse | The nerve “current’ that passes along a neuron |
| Neuron | A nerve cell |
| Neurotransmitter | Molecules released at a synapse to transmit the nerve impulse from one neuron to the next |
| Neutral fat | A fat or triglyceride. Biological compound consisting of three fatty acids linked to one glycerol molecule |
| Neutrophil | White blood cell with granules in the cytoplasm involved in phagocytosis |
| Nictitating membrane | The third eyelid in the cat, tuatara and crocodiles |
| Normal saline | A 0.9% solution of sodium chloride |
| Nuclear membrane | The double layered membrane that surrounds the nucleus |
| Nucleolus | The spherical body within the nucleus, containing RNA |
| Nucleus | The spherical or oval body in the cell that contains the DNA |
| Nutrient | A chemical substance in food that provides energy or assists various body processes |