Aging and Senescence

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Aging and Senescence Lifespans, even of closely related species (e.g. mammals), can be very varied: for example a hamster 3 years, a human 80 years. Changes associated with age are …

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Puberty In Humans

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Puberty In Humans ▶Puberty onset Puberty is a period of rapid body growth and development. accompanied by the secretion of gonadal hormones and the development of sexual maturity, including the …

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The Menstrual Cycle In Women

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The Menstrual Cycle In Women ▶Pre-ovulation After puberty in women, the menstrual (monthly) cycle is established. The production of eggs (oocytes) is cyclical: it involves an interplay of hormones and …

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Mid-Life And Menopause In Humans

Mid-Life And Menopause In Humans ▶Mid-life Mid-life spans the years between puberty and old age (senescence). In men, maximum secretion of testosterone occurs between 18 and 20 years of age; …

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Nonmuscular Movement

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Cytoskeleton Most cells contain cytoskeletal elements comprising contractile filaments of actin and myosin, together with microtubules. This permits shape changes in the cells and facilitates the evolution of specialized mechanisms …

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Veins of the Neck

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Veins of the Neck The veins of the neck include the external jugular, internal jugular, vertebral, and subclavian veins External Jugular Vein The external jugular vein is formed by the …

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Nose (Nasal Cavity)

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Nose (Nasal Cavity) The median nasal septum, consisting of bony and cartilaginous components, subdivides the nasal cavity into a right and a left nasal fossa, Each nasal fossa has anterior …

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Anatomy of Tongue

Anatomy of Tongue The tongue, a muscular organ, is divided for descriptive purposes into the body, which lies relatively free in the oral cavity, and the base, which is fixed …

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Muscle cells Muscle cells are specialized for contraction: every muscular function, from running and jumping, to ventilating the gills or lungs, propelling blood through the vascular system or food through …

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Class Reptilia-  Turtles

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Class Reptilia-  Turtles The reptiles constitute one of the most interesting, and, in general, one of the least known classes of the vertebrates. They are cold-blooded; usually covered with scales, …

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Animal Hormones

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Animal Hormones Vertebrate Endocrine Glands and Hormones Hormones and Nerves Increasing size and complexity in multicellular animals necessitates communication systems for integration and control. Two principal methods are used: Chemical …

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Amphibia. Frogs, Toads, Salamanders

Amphibia. Frogs, Toads, Salamanders The common amphibians are the frogs, toads, and salamanders. They spend part or all of their existence in the water or damp places. Most lay their …

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Human Blood Glucose Control

Human Blood Glucose Control ▶Blood glucose norm Blood glucose control is part of the energy management of the body and is a key homeostatic process. The normal blood glucose load …

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The Gut And Digestion

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Feeding patterns Macrophagous feeders (eat large food particles) include carnivores which eat meat (includes fish-eating piscivores, and insect-eating insectivores, etc.), herbivores which eat vegetation and omnivores which eat a mixed …

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Chemical composition of protoplasm

Chemical composition of protoplasm When protoplasm is studied chemically, it is found to be built up of the same elements that occur in nonliving materials. The 20 elements listed below …

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Cell parts

Protoplasm The cessation of visible activities is due to the cessation of activities within the substance of the body. This living substance’ is known as protoplasm. As long as protoplasm …

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The Mammalian Heart


Heart structure The heart is a muscular pump whose walls are largely made up of cardiac muscle anchored in a fibrous cardioskeleton. Blood returning from body tissues enters the right …

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Blood And Circulation


Functions of Blood Except in very small animals (e.g. flatworms) or those with very low metabolic rates (e.g. jellyfishes), simple diffusion from the surface of the body cannot distribute gases …

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High Altitude Respiration In Mammals

Pressure at high Altitude At sea level, there is approximately 0.2 atmospheres (20 kPa) of pressure driving oxygen from the atmosphere to the mitochondria where it is metabolized; above 8000 …

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