Integumentary System PDF

**INTEGUMENTARY SYSTEM** **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_** **Integumentary system** - Consists of skin and its appendages. - Skin is the largest organ in the body - Appenda...

**INTEGUMENTARY SYSTEM** **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_** **Integumentary system** - Consists of skin and its appendages. - Skin is the largest organ in the body - Appendages include glands, hair, fur, wool, feathers, scales, claws, beaks, horns, hooves, and nails. - Functions - It is a physical barrier that protects animals from microbial infection, injury, ultraviolet rays, chemicals, and toxins. - It also plays a role in waterproofing the body, preventing fluid loss, providing temperature regulation through vasodilation and vasoconstriction, excreting wastes, providing species-specific coloration, sensation, and providing a site for vitamin D synthesis. - Exocrine glands, both sebaceous and sweat, are located in the integumentary system. Sebaceous glands lubricate the skin and discourage bacterial growth on the skin. - Sweat glands regulate body temperature and excrete wastes through sweat. - Hair and nails are other components of the integumentary system. - Hair helps control body heat loss and is a sense receptor. - Nails protect the dorsal surface of the distal phalanx. - **Integument of invertebrates** - Invertebrates like protozoans are covered by delicate cell membrane for their external covering. While some protozoan like the paramecium have firm and ellastic pellicle. - **Arthropod integument** - Consists of a single-layered epidermis which secretes tough cuticle. This cuticle forms the exoskeleton of arthropods. - The thicker inner zone, the procuticle, is composed of protein and chitin (a polysaccharide) - The outer zone of cuticle, is the thin epicuticle. The epicuticle is a nonchitinous complex of proteins and lipids that provides a protective moisture-proofing barrier to the integument. - On snails and some other animals, they secrete calcium carbonate on their shells and others have mucous glands. - **Integument of vertebrates** - The integument of vertebrate is composed of three layers the epidermis, dermis, and hypodermis. 1. **Epidermis** - *Epi* = above; *dermis* = skin - The outermost or most superficial layer of the skin - It is made up of stratified squamous epithelium and a basal layer. - The thickness of the epidermis varies greatly from region to region in all animals. The thickest layers are found in the areas of greatest exposure, such as the foot pads and teats. - 5 Layers of the Epidermis 1. **Stratum basale or stratum germinativum** - The basal or deepest layer of the epidermis. - Cuboidal cells arranged in row. - They multiply to replenish cells lost from the epidermal surface. - **Keratinocytes** are the predominant cell of the epidermis. - Produces **keratin** that protects the epidermis - Responsible for the formation of the epidermal water barrier by making and secreting lipids - Regulate calcium absorption by the activation of cholesterol precursors by UVB light to form vitamin D.  - **Melanocytes** are specialized [skin](https://www.britannica.com/science/human-skin) [cell](https://www.britannica.com/science/cell-biology) that produces the protective skin-darkening [pigment](https://www.britannica.com/technology/pigment) [melanin](https://www.britannica.com/science/melanin). - **Melanin** is the black pigment of the skin that protects the skin from some of the harmful rays of the sun and is responsible for skin pigmentation. - **Albinism** is the absence of normal pigmentation of the skin. - **True albinism** means that the hair, skin , and eyes have no pigmentation. -Melanocyte Melanin Producing Cells Melanin Pigment Stock Vector (Royalty Free) 281633990 \| Shutterstock  - **Merkel cells** serve a sensory function as mechanoreceptors for light touch, and are most populous in fingertips, though also found in the palms, soles, oral, and genital mucosa.  2. **Stratum spinosum** - The prickle or spinous layer. - The layer immediately superficial to the stratum basale. - It contains irregular, polyhedral cells with cytoplasmic processes, sometimes called "spines", that extend outward and contact neighboring cells by desmosomes. - Langerhans cells, a type of dendritic cell, can be found in this layer. - The skins first line defenders. - The thickest layer in hairless regions and in areas of high wear and tear. 3. **Stratum granulosum** - 3-5 cell layers thick immediately superficial to the stratum spinosum. - It contains diamond shaped cells with keratohyalin granules and lamellar granules. - Keratohyalin granules contain keratin precursors that eventually aggregate, crosslink, and form bundles. - Lamellar granules contain the glycolipids that get secreted to the surface of the cells and function as a glue, keeping the cells stuck together. 4. **Stratum lucidum** - It is a thin clear layer - It is filled with **Eleidin**, an intermediate form of keratin. - This layer is not present in all species, but when present, it is found in areas of high wear and tear such as the foot pads. 5. **Stratum corneum** - The horny cells - because its cells are toughened like an animal\'s horn. - The uppermost or superficial layer consisting of 20-30 layers of dead, highly keratinized, and flattened cells. **\ ** 2. **Dermis** - Also called **Corium** - The layer directly deep to the epidermis. - The dermis is composed of blood and lymph vessels, nerve fibers, and the accessory organs of the skin. - Sensory nerve endings in the dermis are the sensory receptors for touch, temperature, pain, and pressure. - Perception is the ability to recognize sensory stimuli. - Tactile perception is the ability to recognize touch sensation. - The dermis also contains connective tissue, which is composed of the following cells: - **Fibroblasts** = fiber-producing cells. Collagen is the major fiber in the dermis. - **Histiocytes** = phagocytic cells that engulf foreign substances; also called tissue macrophages. - **Mast cells** = cells that respond to insult by producing and releasing histamine and heparin. - **Histamine** is a chemical released in response to allergens that causes itching. - **Heparin** is an anticoagulant chemical released in response to injury 3. **Hypodermis** - Also called **Subcutaneous layer.** - The deepest layer of skin - Contains large amount of fat or adipose cells. **Skin Association** 1. **Glands** a. - - - - - b. - - - Produce and secrete water, salt, and waste (sweat) and are located in various regions of the body depending on the species. - Their ducts open directly onto the skin surface through pores. - - - - 2. **Hair** - - - - - 3. **Nails, Claws, Hooves** - - - 4. **Feathers** - Epidermal structure of birds analogous to hair - Used for insulation and thermoregulation, in courtship displays, and for flight 5. **Beaks** - The hard mouth part of bird 6. **Scales** - A small rigid [plate](https://en.wikipedia.org/wiki/Plate_(animal_anatomy)) that grows out of an [animal](https://en.wikipedia.org/wiki/Animal)\'s [skin](https://en.wikipedia.org/wiki/Skin) to provide protection. 7. **Horns** - A permanent pointed projection on the head of various animals.