Integumentary System

Integumentary: is the skin system, the skin is the largest organ in the body.



Epidermis: is the superficial layer of skin that is composed of stratified squamous epithelial cells 

  • It is composed of flattened scale like layers (4 or 5 depending on wether it is thick skin or thin skin) 


  • The epidermis contains 4 different kinds of cells: melanocytes, keratinocytes, tactile/merkel cells and dendritic cells. 


Melanocytes: produce pigment 


Tactile/merkel cells: pick up touch senses 


Keratinocytes: the major skin cells of the epidermal layer, they are a tough fibrous protein that give the epidermis its protective properties. Also produces enzymes to detoxify the body. 


Dendritic cells/Langerhan cells: you see these all over the body. They help fight against pathogens. 



Dermis: is the second major region of the skin and is composed of flexible connective tissue. 


The dermis is composed of 2 layers 

  1. The papillary layer 

  2. The reticular layer 






Subcutaneous layer: it is also known as the hypodermis 

  • It is made up of areolar and adipose tissue but mostly adipose tissue 

  • Anchors to muscles and other underlying tissues to the skin

  • Acts as an insulator 



Hypodermis: the bottom layer of the skin is important for storing fat and connecting the skin to the muscle and bones.

—--> within the hypodermis there is the lamellated corpuscle that is able to sense deep pressure 




Thick skin: found in the palms of the hands, on the fingers and the soles of your feet as it covers layers prone to abrasion 

  • Has 5 layers of keratinocytes 

  • Includes the stratum lucidum 

(stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale/stratum germinativum)



Thin skin: found everywhere else in the body 

  • Only 4 layers of keratinocytes 

  • Missing the stratum lucidum 

  • (stratum corneum, stratum granulosum, stratum spinosum, stratum basale/stratum germinativum) 



Collagen: these are the elastic fibrous proteins that make up the dermis 

  • Gives skin its strength and resilience 



Cleavage lines: represents separations between underlying collagen fiber bundles in the reticular dermis 

  • This is an invisible layer 

  • They run circularly in the trunk & longitudinally in the limbs

  • Surgical incisions on these lines heal faster 



Another word for network: reticulum = network

 

Because the reticular layer of the dermis is made up of a network/reticulum of collagen proteins/fibers 


  • Stratum Basale (Stratum Germinativum): This is the deepest layer of the epidermis, and it contains rapidly dividing cells known as keratinocytes. These cells are responsible for producing new skin cells, which then migrate upwards through the other layers.

  • Stratum Spinosum: Above the stratum basale, you find the stratum spinosum. It consists of several layers of keratinocytes that are becoming flattened and are interconnected by structures called desmosomes.

  • Stratum Granulosum: The stratum granulosum contains flattened keratinocytes that have begun to fill with keratohyalin granules. These granules help to form the proteins that provide strength and waterproofing to the skin.

  • Stratum Lucidum: This layer is only present in thick skin. It is a clear, translucent layer made up of a few rows of dead, flattened keratinocytes. It further contributes to the skin's toughness.

  • Stratum Corneum: The stratum corneum is the outermost layer of the epidermis in thick skin. It is composed of many layers of dead, fully keratinized cells. These cells are continuously shed and replaced by new cells from the deeper layers. The stratum corneum acts as a protective barrier against environmental factors

  • Papillary: Resembling small, nipple-shaped projections or elevations found in clusters

  • Papillary layer: Most superficial layer of dermis with blood supply.

  • Reticulum: a network or mesh of fibrils, fibers or filaments

  • Reticular layer: Deeper layer of the dermis that supplies the skin with oxygen and nutrients (dense irregular connective tissue)

  • Hair: the outgrowth of skin composed of keratin 

  • Dermal papillae: a nipple-like projection of the dermis that may contain blood capillaries or Meissner corpuscles of touch

  • Papillary plexus: branching network covers the blood supply from the papillary layer of the dermis into the epidermis.

  • Cutaneous plexus: Deep network of arteries along the reticular layer.

  • Capillary loops: Tiny, thin-walled blood vessels that form a network and are responsible for the exchange of oxygen, nutrients, and waste products between the bloodstream and surrounding tissues. 

  •  Adipocytes: Cells that make up adipose tissue, commonly known as fat cells. They store energy in the form of fat and play a role in insulation and cushioning. 


keratinocyte: The predominant type of cell found in the epidermis (outermost layer of the skin). These cells produce a protein called keratin, which helps provide structural strength to the skin.


Keratohyalin: A granular protein substance found in keratinocytes. It plays a role in the formation of keratin in the skin, hair, and nails.


Tonofibrils: Filamentous structures within keratinocytes that help in the formation of the skin's structural proteins, including keratin.


Melanocytes: Specialized cells in the skin that produce melanin, the pigment responsible for skin, hair, and eye color. Melanin also provides some protection from the harmful effects of ultraviolet (UV) radiation.


Tactile Cells: Also known as Merkel cells, these are specialized skin cells that are involved in the sense of touch and are found in the epidermis.


Dendritic Cells: Cells of the immune system that are found in various tissues, including the skin. They play a role in capturing and presenting antigens to immune cells, initiating immune responses.


Eccrine Gland: A type of sweat gland that is distributed throughout the skin. It produces sweat, which helps regulate body temperature and is mostly composed of water, salt, and small amounts of waste products.


Merocrine Gland: A type of exocrine gland that releases its secretions through exocytosis. Eccrine sweat glands are an example of merocrine glands.


Apocrine Gland: A type of sweat gland found in areas like the armpits and groin. Apocrine sweat is thicker and contains more proteins than eccrine sweat. It can develop an odor when it comes into contact with bacteria on the skin.


Sebum: An oily, waxy substance produced by sebaceous glands. Sebum helps keep the skin and hair lubricated and provides some protection against bacteria and fungi.


Sebaceous Gland: Glands that secrete sebum, typically associated with hair follicles. They are important for maintaining healthy skin and hair.


Sudoriferous Gland: A general term for sweat glands. It encompasses both eccrine and apocrine glands.


Sweat Gland: A gland that produces sweat, which helps regulate body temperature and eliminate waste products.


Sweat: A watery secretion produced by sweat glands. It consists of water, electrolytes, and waste products and is released through the skin to cool the body and maintain homeostasis.


Ceruminous Gland: Glands found in the ear canal that produce cerumen (earwax), which helps protect the ear and trap debris.


Cerumen: Commonly known as earwax, it is a waxy substance produced by ceruminous glands in the ear canal. It helps lubricate and protect the ear canal.


Mammary Glands: Specialized glands in the female breast that produce milk to nourish infants.


Melanoma: A type of skin cancer that arises from melanocytes. It is the most aggressive form of skin cancer and can spread to other parts of the body.


Melanin: A pigment responsible for the color of skin, hair, and eyes. It is produced by melanocytes and provides some protection from the harmful effects of UV radiation.


Melanosomes: Specialized organelles within melanocytes that contain melanin.


Dermcidin: A protein found in sweat that has antimicrobial properties and helps protect the skin from infection.


Subcutaneous Injection: A method of administering medication by injecting it into the layer of tissue just beneath the skin, known as the subcutaneous tissue.


Holocrine Secretion: A mode of glandular secretion where entire cells, along with their contents, are released as a secretion. Sebaceous glands are an example of holocrine glands.


Alveolar Glands: Glands that have a structure resembling small sacs (alveoli) and are found in various parts of the body, including the mammary glands. They can produce various substances, including milk in mammary glands.


Accessory structures: of the skin include the hair, nails, sweat glands and sebaceous glands (know the labels of the diagram from the powerpoint)