Describe the structural characteristics of the epidermis that contribute to its ability to protect the surface of an animal
What will be an ideal response?
Multiple layers of cells in stratified squamous epithelium help resist friction. Keratin of intermediate filaments provides strength to tissue by binding cells tightly together and to underlying tissue, thus creating a barrier to microbes. Lamellar granules of keratinocytes produce a lipid rich, water repellent (sealant) to protect from dehydration and entry of foreign materials. Melanin, produced by melanocytes, protects underlying tissue from UV light. Sebum secreted onto the surface helps protect from dehydration and microbial invasion. Intraepidermal macrophages (Langerhans cells) participate in immune response to microbial invasion.
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Bicarbonate that protects the duodenum from peptic ulcers comes from all of the following EXCEPT ________.
A. Brunner's cells B. pancreatic juice C. adherent layer of mucus D. stomach
During the absolute refractory period which of the following is true?
A) The signal grows weaker with distance. B) It is possible to trigger a new action potential, but only with an unusually strong stimulus. C) The neuron fires at its maximum voltage if a stimulus depolarizes the neuron to threshold. D) If a neuron reaches threshold, the action potential goes to completion. E) No stimulus of any strength will trigger a new action potential.
The trophoblast of the implanted fertilized egg ultimately develops into the
A) Allantois. B) Amniotic cavity. C) Placenta. D) Zona pellucida.
A woman who drops something on her foot might injure which of the following bones?
A. Metacarpals B. Cuneiform C. Pisiform D. Vomer E. Lunate