Page 52 - 84 human physiolofy part-1

Chapter 3

brings about dilation of the blood vessels supplying the skin. The increase in skin blood flow allows
heat to be lost more rapidly so that body temperature does not rise above the normal homeostatic range.
The rate of heat loss can also be boosted by the production of sweat, which takes up additional heat as
it evaporates. Conversely, if heat production is less than required, the dermal vessels constrict, sweating
stops, and heat is conserved by the body.

Glossary

Areolar
Areolar connective tissue is a pliable, mesh-like tissue with a fluid matrix and functions to
cushion and protect body organs. It acts as a packaging tissue holding the internal organs together
and in correct placement.

Basal lamina
Basal lamina (often erroneously called basement membrane) is a layer on which epithelium sits.
This layer is composed of an electron-dense layer (lamina densa) between two electron-lucid
layers (lamina lucida), and is approximately 40-50 nm thick (with exceptions such as the 100-200
nm glomerular basement membrane).

Dermis
The dermis is the layer of skin beneath the epidermis that consists of connective tissue and
cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a
basement membrane.

Epidermis
The epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the
body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.

Fibroblasts
A fibroblast is a cell that makes the structural fibers and ground substance of connective tissue.

Hair follicle
A hair follicle is part of the skin that grows hair by packing old cells together.

Hypodermis
The hypodermis (also called the hypoderm), is the lowermost layer of the integumentary system
in vertebrates. It is derived from the mesoderm, but unlike the dermis, it is not derived from the
dermatome region of the mesoderm.

Impetigo
This is a superficial skin infection most common among children age 2–6 years. People who play
close contact sports such as rugby, American football and wrestling are also susceptible,
regardless of age. The name derives from the Latin impetere ("assail"). It is also known as school
sores.

Melanocytes
These are cells located in the bottom layer of the skin's epidermis and in the middle layer of the
eye, the uvea. Through a process called melanogenesis, these cells produce melanin, a pigment in

52 | Human Physiology