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The Integumentary System 8/27/24, 3:47 PM Platform | Study Fetch (00:00:13 - 00:00:23)The integumentary system is the largest organ of the human body. It acts as a protective barrier to the external environment and controls body t...

The Integumentary System 8/27/24, 3:47 PM Platform | Study Fetch (00:00:13 - 00:00:23)The integumentary system is the largest organ of the human body. It acts as a protective barrier to the external environment and controls body temperature. It is also a major sensory organ. Lesson Overview (00:00:23 - 00:00:33) 1. Epidermis 2. Dermis 3. Hypodermis The Epidermis (00:00:33 - 00:00:56) The epidermis is the outermost layer of the integumentary system. It is thin and avascular (without blood vessels). It is made of stratified squamous cells and keratinocytes. Layers of the Epidermis (00:00:56 - 00:01:32) Stratum Corneum: Contains corneocytes, which are dead, fully differentiated keratinocytes filled with keratin, making them mechanically tough. Stratum Lucidum: Made of dead keratinocytes, found only in the hands and feet. Stratum Granulosum: Made of keratinocytes that have Lamar bodies, which are secreted. This layer is the skin's water barrier. Stratum Spinosum: Contains the "linger hand cells" with desmosomes that give the skin strength and flexibility. (00:01:32 - 00:01:43) The epidermis is the outermost layer of the skin and provides a protective barrier. The Dermis (00:01:43 - 00:02:02) "If you were to take like a section of the skin and you were to look at it, uh these cells actually, you would see these, these thin, you can kind of see them here on these thin" The dermis is the layer of skin beneath the epidermis. It provides structural support and contains blood vessels, nerves, and other structures. The Hypodermis https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 1/6 8/27/24, 3:47 PM Platform | Study Fetch (00:02:02 - ) The hypodermis is the deepest layer of the integumentary system. It is composed of adipose (fat) tissue that provides insulation and cushioning. The Layers of the Epidermis (00:02:02 - 00:02:19)The epidermis is composed of several distinct layers, each with its own unique characteristics and functions. These layers are: Stratum Corneum The outermost layer of the epidermis Composed of dead, flattened keratinocytes Provides a protective barrier against the environment Stratum Lucidum A thin, transparent layer found only in thick skin (palms and soles) Composed of flattened, clear keratinocytes Stratum Granulosum Contains keratinocytes that are beginning to produce keratin Keratin gives the cells a granular appearance Stratum Spinosum Also known as the "spiny layer" Contains keratinocytes connected by desmosomes (strong, flexible connections) Desmosomes give the layer a spiny appearance Stratum Basale The deepest layer of the epidermis Contains the stem cells that renew the epidermis Also contains Merkel cells (sensory cells) and melanocytes (pigment-producing cells) (00:02:19 - 00:02:29)The stratum basale is the stem cell source of the skin. If the upper layers of the epidermis are damaged, the stem cells in the stratum basale will proliferate and push new cells upwards, forming new layers of skin. (00:02:29 - 00:02:42)The layers of the epidermis can be remembered using the mnemonic "Come, let's get some boba": Corneum Lucidum Granulosum Spinosum Basale (00:02:42 - 00:02:56)If the upper layers of the epidermis are damaged, such as from a severe sunburn, the keratinocytes in those layers will undergo apoptosis (programmed cell death) and die. The stem cells in the stratum basale will then proliferate and push new cells upwards, forming a new epidermis. (00:02:56 - 00:03:10)The stratum basale contains two important cell types: https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 2/6 8/27/24, 3:47 PM Platform | Study Fetch Merkel Cells Sensory cells that detect touch and pressure Predominantly found in areas of the skin with high sensitivity, such as the fingertips Melanocytes Cells that produce the pigment melanin Responsible for skin pigmentation and protection from UV radiation (00:03:10 - 00:03:35)Merkel Cells: Located in the stratum basale Sensitive to light touch, pressure, and the sensation of edges Play a role in the sense of touch and proprioception (awareness of body position) More abundant in areas of the skin with high sensitivity, such as the fingertips and lips Melanocytes: Also located in the stratum basale Produce the pigment melanin Melanin provides protection from UV radiation and determines skin color (00:03:35 - 00:03:46)In summary, the epidermis is composed of several distinct layers, each with its own unique functions and cell types. The stratum basale contains the stem cells that renew the epidermis, as well as Merkel cells and melanocytes, which play important roles in sensory perception and skin pigmentation, respectively. Melanocytes and Melanin (00:03:57 - 00:04:10) A mole is a pile-up of melanocytes in the basal layer of the epidermis Freckles are areas where melanocytes have secreted more melanin than other areas Melanocytes and melanin are located in the basal layer of the epidermis (00:04:10 - 00:04:25) The stratum basale consists of keratinocytes and melanocytes This is where melanin is produced and distributed to surrounding keratinocytes Melanin helps protect the skin from UV radiation damage (00:04:25 - 00:04:38) The dermis is a network of dense, irregular connective tissue It has two layers: the papillary dermis and the reticular dermis (00:04:38 - 00:04:54) The papillary dermis has dermal papillae that project into the epidermis These papillae increase the surface area for exchange of nutrients and gases The papillary dermis and reticular dermis can be examined to diagnose certain skin diseases (00:04:54 - 00:05:08) The dermal papillae increase the surface area for exchange between the epidermis and dermis Changes in the papillae can indicate certain skin diseases (00:05:08 - 00:05:28) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 3/6  The epidermis is avascular, meaning it does not have its own blood supply 8/27/24, 3:47 PM Platform | Study Fetch The papillae and underlying dermis provide the epidermis with nutrients and oxygen (00:05:28 - 00:05:42) The epidermis relies on the dermis for its blood supply and nutrient exchange Key Terms and Concepts: Melanocytes Melanin Moles Freckles Stratum basale Papillary dermis Reticular dermis Dermal papillae Avascular epidermis Tables: Layer Components Epidermis Keratinocytes, melanocytes Dermis Papillary layer, reticular layer Block Quote: The epidermis is avascular, meaning it does not have its own blood supply. The Layers of the Skin (00:05:42 - 00:05:54)The epidermis, the outermost layer of the skin, does not have a direct blood supply. Any nutrients or substances the epidermis needs must come from the underlying dermis layer. (00:05:54 - 00:06:08)The Reticular Dermis: Contains reticular fibers, collagen, and elastic fibers Also contains blood vessels, sensory receptors, hair follicles, and glands This layer is the source of nutrients, projections, and secretions for the skin (00:06:08 - 00:06:22)The Layers of the Dermis: The papillary dermis is the layer on top of the reticular dermis This mnemonic helps remember the relationship: "The papillary dermis lies on top of the reticular bed" (00:06:22 - 00:06:38)Hair Follicles: Hair follicles are found in the reticular dermis Hair is made of the protein keratin and projects up through the epidermis https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 4/6 8/27/24, 3:47 PM Platform | Study Fetch (00:06:38 - 00:06:55)Glands in the Dermis: The dermis contains glands, which are important for skin function Endocrine glands secrete directly into the blood Exocrine glands secrete their product through a duct to an external surface like the skin (00:06:55 - 00:07:19)Types of Exocrine Glands: Sebaceous (oil) glands Eccrine (sweat) glands Mostly found in the armpits and soles of the feet Important for thermoregulation Integumentary System (00:07:19 - 00:07:31) Apocrine glands produce oily and viscous secretions These glands are present in the hair follicles of the: Armpits Nipples Ear canal Eyelids Nostrils Pubic area The secretions help trap bacteria and protect the skin (00:07:31 - 00:07:54)Mnemonic for types of sweat glands: Apocrine glands are more oily and found in hair follicles (armpits, ear canal, etc.) Eccrine glands are everywhere, especially in the armpits, hands, and feet Sebaceous glands secrete sebum (oily wax) into hair follicles to lubricate and waterproof hair and skin (00:07:54 - 00:08:07) Sebaceous glands secrete sebum (oily wax) into hair follicles This helps oil and lubricate the hair follicle Sebaceous glands are found everywhere except the palms and soles of the feet (00:08:07 - 00:08:20)Mnemonic for sebaceous glands: Sebaceous glands secrete sebum See them lubricate and waterproof hair and skin Think of the movie "The Little Mermaid" with Sebastian the crab (00:08:31 - 00:08:45)The Hypodermis (Subcutaneous Layer): Located underneath the dermis Contains nerves, blood vessels, and muscle areas Made of loose connective tissue and adipose (fat) tissue (00:08:45 - 00:08:56) The hypodermis stores fat It is a layer of loose connective tissue and adipose (fat) tissue https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 5/6  Key Points: 8/27/24, 3:47 PM Platform | Study Fetch Apocrine Glands: Produce oily, viscous secretions Found in hair follicles of specific areas (armpits, nipples, etc.) Help trap bacteria and protect skin Eccrine Glands: Sweat glands found all over, especially in armpits, hands, and feet Sebaceous Glands: Secrete sebum (oily wax) into hair follicles Lubricate and waterproof hair and skin Found everywhere except palms and soles Hypodermis (Subcutaneous Layer): Underneath the dermis Contains nerves, blood vessels, muscle Made of loose connective and adipose (fat) tissue Stores fat https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cb9f069b6d6b89c5eb0/document?go=note 6/6