Human Body Temperature Control, Cutaneous Physiology, and Clinical Thermometry

Hypothalamic Thermoregulation and Body Temperature Control

  • Definition of Body Temperature:

    • Body temperature is defined as the physiological equilibrium between the production of heat by the organism and the loss of heat to the environment.
    • This equilibrium is dynamically maintained and regulated by the central thermoregulatory center situated in the hypothalamus.

  • Anatomy and Function of the Thermoregulatory Center:

    • The central thermoregulatory center is located within the hypothalamus.
    • It functions analogously to a thermostat to control body temperature.
    • It consists of two primary functional areas:
    • Anterior hypothalamic area (Área hipotalámica anterior).
    • Posterior hypothalamic area (Área hipotalámica posterior).

  • Anterior Hypothalamic Area Functionality:

    • Governs mechanisms responsible for heat loss when the body temperature of the organism rises.
    • Induces arterial vasodilation (vasodilatación) in the arteries of the skin.
    • Stimulates sweating (sudoración) to facilitate evaporative cooling.

  • Posterior Hypothalamic Area Functionality:

    • Governs heat concentration and increased heat production when the body temperature of the organism drops (desciende).
    • Induces arterial vasoconstriction (vasoconstricción arterial) to reduce peripheral blood flow and minimize heat loss.

Anatomy and Physiology of the Skin

  • Definition of the Skin:

    • The skin is the protective organ covering the entire exterior surface of the body.
    • It isolates internal anatomical structures from the surrounding external environment.

  • Structural Layers of the Skin:

    • Epidermis: The outermost epithelial layer.
    • Dermis: The middle structural layer containing blood vessels and connective tissues.
    • Hypodermis (Subcutaneous Fatty Tissue / Tejido Graso Subcutáneo): The deep layer composed of adipose tissue that provides insulation and structural support.

  • Cutaneous Appendages (Anexos Cutáneos):

    • Eccrine sweat glands (glándulas sudoríparas ecrinas).
    • Apocrine sweat glands (glándulas apocrinas).
    • Pilosebaceous apparatus (aparato pilosebáceo).
    • Nails (uñas).

  • Physiological Functions of the Skin:

    • Provides cutaneous permeability (permeabilidad cutánea).
    • Interacts continuously with the external environment.
    • Regulates systemic body temperature.
    • Serves as a physical barrier against external physical, chemical, and biological aggressions.

  • Environmental Stimuli and Microorganism Defense:

    • The skin continuously encounters four major categories of environmental stimuli:
    • Mechanical stimuli.
    • Thermal stimuli.
    • Radiation stimuli.
    • Chemical stimuli.
    • Protects internal structures against invasion by external aggressors, specifically microorganisms.

  • Role of Dermal Blood Vessels:

    • Dermal blood vessels (vasos sanguíneos dérmicos) play essential roles in:
    • Regulation and control of systemic blood pressure (presión arterial).
    • Regulation of body temperature.

Clinical Temperature Measurement and Thermometry

  • Temperature Units and Numerical Ranges:

    • Degrees Celsius (Grados Celsius): Clinical scale measuring temperature within a range between 35∘C35^\circ\text{C} and 42∘C42^\circ\text{C}.
    • Degrees Fahrenheit (Grados Fahrenheit): Clinical scale measuring temperature within a range between 95∘F95^\circ\text{F} and 107.6∘F107.6^\circ\text{F}.

  • Normal Adult Temperature Range:

    • The physiological normal range for body temperature in adults is 36.1∘C−37.1∘C36.1^\circ\text{C} - 37.1^\circ\text{C}.

  • Components of a Mercury Thermometer:

    • Bulb (Bulbo): The reservoir holding liquid mercury.
    • Mercury (Mercurio): The liquid metal thermometric fluid.
    • Capillary Tube (Tubo capilar): The narrow inner glass tube through which expanding mercury travels.
    • Scale (Escala): The background reference plate displaying numerical values.
    • Graduation (Graduación): The marked division lines indicating specific temperature increments.
    • Stem (Tallo): The protective outer glass housing surrounding the capillary tube and bulb.

  • Axillary Temperature Constant Adjustment:

    • A constant value of 0.5∘C0.5^\circ\text{C} must be added to the raw temperature reading when measured in the axillary fossa (hueco axilar).
    • Physiological Justification: Skin offers cutaneous permeability and acts as a physical barrier isolating internal core body temperature from external environmental ambient temperature, making skin surface measurement lower than true core temperature.

  • Measurement Duration Protocols by Anatomical Site:

    • Axillary Fossa (Hueco Axilar): The thermometer must remain in place for 5 minutes5\text{ minutes} (noted to be less accurate / es menos exacto).
    • Physiological Orifices (Orificios Fisiológicos - Mouth, Rectum, and Vagina / Boca, Recto y Vagina): The thermometer must remain in place for 3 minutes3\text{ minutes}.