Week 13 The Integumentary System

The integumentary system consists of the skin and its derivatives: hair, nails, and glands

Objective 1: Structures of the Integument The two primary skin layers are: Epidermis: superficial layer made of keratinized stratified squamous epithelium Dermis: consists of areolar tissue and dense irregular connective tissue Hypodermis: attaches skin to underlying structures; made of areolar tissue and variable amounts of adipose

The epidermis has either 4 or 5 cell layers Thin skin has 4 layers; the stratum lucidum is absent Thick skin of the palms and soles of the feet has 5 layers

Layers of the Epidermis: Layer Structure Stratum corneum 20-30 rows of flat dead keratinocytes Stratum lucidum 2-3 rows of dead keratinocytes, found only in thick skin Stratum granulosum 3-5 rows of flat keratinocytes Stratum spinosum 8-10 rows of flat keratinocytes, Stratum basale single layer of keratinocytes; some melanocytes, and Merkel cells

Composed of connective tissue epidermis The Dermis is: Deep to the epidermis Composed of connective tissue Consists of a superficial papillary layer and a deep reticular layer Contains sensory receptors, nerve fibers, glands, and hair follicles Papillary layer dermis Reticular layer

Hair follicles and sebaceous glands are epithelial derivatives that live in the dermis

Skin derivatives found in the dermis: Arrector pili muscle Sebaceous (oil) gland Hair Structures

Connective tissue root sheath Epithelial root sheath HAIR STRUCTURES Hair shaft Sebaceous gland Hair root Connective tissue root sheath Arrector pili muscle Epithelial root sheath (Hair follicle) Hair Bulb Hair Papilla

Hair Structures Hair Bulb Hair Shaft Hair Root (visible hair) (embedded)

Histology – Hair Structures Hair Root Hair Follicle Hair Bulb Hair Papilla

Histology – Hair Structures Sebaceous (oil) gland Hair shaft Hair follicle Hair root Arrector pili Hair Root Hair Follicle Sebaceous (oil) gland

Sudoriferous (sweat) glands are also found in the dermis

Other important structures found in the dermis are cutaneous sensory receptors

Sensory receptors can be “encapsulated” or “unencapsulated” nerve endings Connective tissue capsule Free Nerve Ending Encapsulated Nerve Ending

Free nerve endings mediate the following sensations: Nociceptors detect pain Thermoreceptors detect heat and cold Proprioceptors detect stretch Root hair plexus detect hair movement Root hair plexus Free nerve ending in the epidermis

Encapsulated Receptors Pacinian corpuscles mediate deep pressure Meissner’s corpuscles mediate light touch

Objective 2: Plotting Eccrine Sweat Gland Distribution Follow the instructions on page 61 of the lab manual Do Not perform this test if you are allergic to iodine The purpose of this experiment is to compare the density of eccrine sweat glands on the forehead, anterior antebrachium, palmar surface of the hand, and the crural region Class data will be gathered

Objective 3: General Sensation Perform each experiment in pairs, one member is the subject the other is the recorder. Then switch roles and perform the experiments again. Some data will be collected from everybody and class data used in your report. You are required to write a lab report for these series of experiments. Follow the format in your lab manual, and the instructions given by your lab instructor. The lab report is due the week after the lab practical