LAB 4 EXERCISE 4-4 Histology: Hair * Hair follicle * Dermal papilla * Sebaceous gland * Eccrine sweat gland * Stratified squamous epithelium * Areolar CT * Dense irregular CT.
The Correct Answer and Explanation is:
Here are the correct identifications for the labeled structures:
- Stratified squamous epithelium
- Dermal papilla
- Dense irregular CT
- Hair follicle
- Sebaceous gland
- Hair
- Stratified squamous epithelium
- Eccrine sweat gland
Explanation
This image displays two histological cross sections of skin, a complex organ composed of the epidermis, dermis, and associated accessory structures. The labels point to these various components, which are essential for protection, sensation, and thermoregulation.
The image on the left details the interface between the epidermis and dermis. Label 1 correctly identifies the stratified squamous epithelium. This tissue forms the epidermis, the skin’s outermost protective barrier. Its multilayered structure is ideal for resisting abrasion and preventing pathogen entry. Below this, label 2 indicates a dermal papilla, one of the many fingerlike projections of the dermis that extend into the epidermis. These papillae increase the surface area for nutrient exchange from blood vessels within and strengthen the connection between the two skin layers. They are composed of areolar connective tissue. Label 3 points to the dense irregular connective tissue that makes up the reticular layer of the dermis. This thick, tough layer contains a meshwork of collagen and elastin fibers, providing the skin with significant strength and elasticity.
The image on the right provides a detailed view of a hair and its associated glands. Label 4 shows the hair follicle, the structure within the dermis responsible for producing hair. Label 6 points to the hair shaft itself, a filament composed of tightly packed, keratinized cells. Attached to the follicle is the sebaceous gland, indicated by label 5. This exocrine gland releases oily sebum to waterproof and lubricate the hair and surrounding skin, preventing them from becoming dry and brittle. Label 7 again points to the superficial stratified squamous epithelium of the epidermis. Deep within the dermis, label 8 highlights an eccrine sweat gland. Its characteristic coiled, tubular appearance is clearly visible. These glands play a crucial role in thermoregulation by secreting sweat onto the skin’s surface, which cools the body as it evaporates.
