THE DERMIS OF THE SKIN

The dermis is the layer of the skin beneath the epidermis. It  makes up about 90% of the skin's thickness. It has:

• Blood vessels
• Hair follicles - This is the tube that surrounds the hair and nourishes it.
• Lymphatic vessels - These drain the lymph in the skin. The lymph contains cells that fight infections. 
• Sebaceous glands - These glands produce sebum. This is the oily substance that lubricates the skin and keeps it waterproof. It keeps the skin smooth and supple. It also helps to fight off bacteria and fungal infections.
• Sweat glands - Produce sweat. There are two types: Apocrine and Eccrine sweat glands. Apocrine sweat glands are found in the armpit and pubic areas. They produce milky sweat that can encourage bacteria growth. Eccrine sweat glands are found in the other parts of the body. 
• Nerve endings - These include touch, pain, pressurs and temperature sensors.
• Collagen and Elastic fibers - These are connective tissues that help to keep the skin tough and elastic.

The dermis consist of two layers. The upper layer is called the papillary dermis and the lower one is called reticular dermis. The papillary layer is thinner than the reticular layer. The papillary layer contains a lot of blood vessels that help to nourish the epidermis and to regulate the body's temperature. The reticular layer has collagen fibers arranged parallel to the skin to help in stretching and maintenance of the strength of the skin. It supports the hair follicles, sweat and sebaceous glands. 

THE LAYERS OF THE EPIDERMIS OF THE SKIN

The epidermis of the skin refers to the topmost layer. It is composed of five layers. From the surface to the deep layers, the names are:

1. Stratum corneum
2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum basale or germinativum

STRATUM CORNEUM
This layer consists of dead cells with a hard protein envelope. These cells contain keratin surrounded by lipid. It is a tough water resistant layer. They are flat, anucleated  and cornified cells.

STRATUM LUCIDUM
This layer consists of dead cells containing dispersed keratohyalin granules. This layer is found in thick thick skins only such as the palm and soles.

STRATUM GRANULOSUM
This layer consists of cells that contain keratohyalin granules and lamellar bodies that have released lipids. They, therefore, look granular. The cells are covered by hard protein. They are polygonal cells with basophylic granules.

STRATUM SPINOSUM
This layer consists of cells that are accumulating keratin fibers and lamellar bodies. The are cuboidal like cells and desmosomes in between.

STRATUM BASALE
The cells in this layer undergo mitosis (cell division) to reproduce the top layers. The are columnar- like cells. The keratinocytes arise from this layer.They produce keratin. Keratin makes our skin tough. It provides protection from microorganisms, physical harm, and chemical irritation.  


Here is a diagram illustrating the layers.

COMPREHENSIVE OVERVIEW OF ANATOMY AND PHYSIOLOGY

This is a great website with a comprehensive overview of anatomy and physiology. Click this link to visit the site.

In future, this website will also become a good resource to you in your medical practice. It gives you insight into various medical conditions and their treatments.

STUDY SKILLS RESOURCES

Study skills are the key to college success. Below, you will find various links to online resources on how to study effectively in college. You do not need to apply all strategies in your learning all at once. An effective approach would be to choose two or three strategies, apply them, and after a few weeks reassess if those strategies worked for you.

Learning Styles Inventory
This questionnaire determines the best way you learn; visually, auditorily, or kinesthetically. Use the strategies provided to increase your chances of success.

Motivating Yourself 
Motivation plays a major role in a person’s success. Read about what you can do to continually be motivated in doing well during your college years and beyond.

Time Management
Research has shown that managing your (professional or personal) time effectively leads a person to be successful and have less stress in their lives.

Preparation for Class
Read about what you need to do before class so that you are well prepared for it.

Note-Taking Skills
Why do you need to review your notes?

Note-Taking Skills
Writing every word a professor says or every word written on the board does not automatically make you a good note-taker. Implement some of the strategies suggested to improve your note-taking skills and ultimately, your notes will take on new meaning.

Preparation for a Test
It is not enough to read over your notes the day before a test. To aim for an A on a test, you must begin studying for it days before. Follow the given suggestions so that you can get that top grade.

Test-Taking StrategiesYou arrive to class exactly on time, put your name on the test paper and proceed to “barrel” through the questions. This is not conducive to you doing well on the test. Read about what you should do on the day of a test.

Dealing with Test Anxiety
If you find yourself saying “I never do well on math tests.” or “I study for days and then I blank when I take the test.”, then you would find it helpful to follow advice on how to ease your apprehension about taking math tests.

Post-Test Strategies
Don’t stick your graded test paper into your book bag and forget about it. Read about the wealth of information a returned test with teacher’s comments gives you so that you do better next time.

TYPES OF JOINTS

Joints occur at regions where two bones meet. They are classified as

• Immovable joints: Also known as fixed joints.  There is relatively no movement between the bones. There is no cartilage between the joints. Examples: Bones of the cranium and facial bones that articulate with the teeth
• Movable joints: Also known as synovial joints. The bones of this joints are capable of movements. The bones are separated by cartilage called articular cartilage. The movement may be partial or freely moveable.
• Partially moveable joints: Very limited range of movement.            Example: The joint between the vertebrae; The joints of the cranium; The joints of the hip bones.
• Freely moveable joints: There are free movements between the articulating bones. The articular surfaces are covered with cartilage. This articular cartilage reduces the friction between the two surfaces of bones making the joint. It is covered by a synovial membrane which forms a closed sac. This sac contains a fluid called synovial fluid. The synovial fluid helps in lubricating the joint to reduce friction. 

Types of freely moveable joints 

Classification is based on the degree of movement that they allow. 

• Hinge joints: These joints allow the backward and forward movement in only one plane. Examples: Elbow and knee joints
• Ball and Socket joints: These joints allow movements in multiple planes. Examples: Shoulder and hip joints
• Pivot joints:  Only rotational movements are possible in these joints. Examples: The joint between the first and second cervical (neck) bones.

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