Medicine- Learning Objectives for weeks 1-3

LO: To identify the function of the 4 main tissues (epithelial, connective, muscular, nervous)

To identify the structure and function of tissue sub-types and aggregates.

Epithelial tissue: is a sheet of cells that covers a body surface or lines a body cavity. Two forms occur in the human body:

1.) Covering and lining epithelium- forms the outer layer of the skin; lines open cavities of the digestive and respiratory system; covers the walls of organs of the closed ventral body cavity.

2.) Glandular epithelium- surrounds glands within the body.

Epithelial sub types: Simple (squamous, cuboidal, columnnar, ciliated) 

Compound (Stratified)

Simple epithelia– consist of a single cell layer (found where absorption, secretion, and filtration occur).

Stratified epithelia– are composed of two or more cell layers stacked on top of each other (typically found in high abrasion areas where protection is needed).

Simple squamous epithelium– are close fitting and flattened laterally. They’re found where filtration occurs (kidneys, lungs) and they resemble the look of a fried egg. Two simple squamous epithelia in the body have special names reflecting their location.

Simple cuboidal epithelium– consists of a single layer of cells with the same height and width. Functions include secretion and absorption (located in small ducts of glands and kidney tubules

Simple columnar epithelium– single layer of tall, closely packed cells that line the digestive tract from the stomach to the rectum. Functions include absorption and secretion. They contain dense microvilli on their apical surface . Some simple columnar epithelia may display cilia on their free surface also.

Simple ciliated epithelium- function of ciliated epithelial cells is to move secretions and foreign bodies away with a certain direction of rapid, wave-like motions from the hair-like structures that cover their free surfaces

Compound (stratified): 

Stratified cuboidal epithelium– It’s mainly found in the ducts of glands (sweat glands, mammary glands) and is typically has two layers of cuboidal cells.

Stratified columnar epithelium– is also rare in the human body. Small amounts are found in the pharynx, male urethra, and lining of some glandular ducts. Stratified columnar epithelium occurs in transition areas (junctions) between other epithial types.

Connective Tissues: serves a connecting function. It supports and binds other tissues in the body. Unlike epithelial tissue which has cells that are closely packed together, connective tissue typically has cells scattered throughout an extracellular matrix of fibrous proteins and glycoproteins attached to a basement membrane.

Connective sub types: Adipose (fat), cartilage, bone, fibrous, blood

Adipose tissue: is a form of loose connective tissue that stores fat. Adipose lines organs and body cavities to protect organs and insulate the body against heat loss. Adipose tissue also produces endocrine hormones.

Cartilage: form of fibrous connective tissue that is composed of closely packed collagenous fibers in a rubbery gelatinous substance called chondrin. Cartilage also provides flexible support for certain structures in adult humans including the nose, trachea, and ears.

Bone: is a type of mineralized connective tissue that contains collagen and calcium phosphate, a mineral crystal. Calcium phosphate gives bone its firmness.

Blood: considered to be a type of connective tissue. Even though it has a different function in comparison to other connective tissues it does have an extracellular matrix. The matrix consists of the plasma, while red blood cells, white blood cells, and platalets are suspended in the plasma.

Muscular tissue: As the name indicates, this tissues makes muscles of the body. This tissue is of 3 types as:

1.) skeletal muscle tissue

2.) cardiac tissue

3.) smooth muscle tissue.

Muscular sub types: stirated, smooth, cardiac

Striated muscles: are present attached to skeletal system, especially long bones. They also have bands or striation along the length. They are voluntary i.e. they are under the control of our will. They help in movement from one place to another.

Smooth muscles: are spindle or cone shaped in structure. They help in contraction and relaxation of man organs like lungs, stomach, uterus etc.

Cardiac muscles: are present in the heart. They like skeletal muscles have striations in them. But the difference is, they have branches. This muscle helps to pump blood by the heart.

Nervous tissue: This tissue is mostly present in the brain and spinal cord. It has two types of tissue as nervous cell and neuroglia.

Nervous syb types: Neurons, Glial Cells

Neurons: (nerve cells) are sensitive to various types of stimuli such as heat/cold, light/dark, pressure. They transmit electrical nerve impulses thereby moving information about the body.

Glial cells: they compose a voluminous support system that is essential to the proper operation of nervous tissues and the nervous system. Unlike neurons, glial cells do not have axons, dendrites or conduct nerve impulses. Neuroglia are typically smaller than neurons and are about three times more numerous in the nervous system.

Tissue aggregates: combined to form larger structures- 

• Fascia,
• ligaments,
• tendons
• Joints: fibrous, cartilaginous, synovial

Fascia: sheet-like membrane whhich surrounds organs.

Ligaments: Elastic fibres, some elasticity, join bone to bone, bone to cartilage or cartilage to cartilage.

Tendons: Attach muscle to bone or muscle to cartilage.

Joints-

Fibrous: Fibrous joints contain fibrous connective tissue and cannot move; fibrous joints include sutures, syndesmoses, and gomphoses.

Cartilaginous: contain cartilage and allow very little movement; there are two types of cartilaginous joints: synchondroses and symphyses

Synovial joints: are the only joints that have a space (a synovial cavity filled with fluid) between the adjoining bones.

To describe the composition of blood and the function of the components (platelets, red blood cells, white blood cells)

Composition of blood: 

Blood makes up about 8% of the human body weight. It contains: erythrocytes, leucocytes, thrombocytes (platelets) and plasma). The volume percentage of all blood cells in the whole blood is about 45% in adults. The rest consists of liquid plasma (e.g. water, plasma proteins, electrolytes etc.).

Blood transports materials and heat around the body, and helps to protect against disease. It contains:

• Plasma
• Red blood cells
• White blood cells
• Platelets

Function of components:

Plasma: 

• Fluid part of blood
• Carries carbon dioxide, hormones and waste

Red blood cells:

• Contain haemoglobin which carries oxygen
• Made in the bone marrow. The more you train the more red blood cells are made.

White blood cells:

• An important part of the immune system, they produce antibodies and destroy harmful microorganisms
• Made in the bone marrow

Platelets:

• Clump together to form clots
• Protect the body by stopping bleeding

To identify the structure and function of three types of blood vessel (artery, vein, capillary)

Arteries:

• Carry blood away from the heart (always oxygenated apart from the pulmonary artery which goes to the lungs)
• Have thick muscular walls
• Have small passageways for blood (internal lumen)
• Contain blood under high pressure

Veins:

• Carry blood to the heart (always de-oxygenated apart from the pulmonary vein which goes from the lungs to the heart)
• Have thin walls
• Have larger internal lumen
  
• Contain blood under low pressure
• Have valves to prevent blood flowing backwards

Capillaries:

• Found in the muscles and lungs
• Microscopic – one cell thick
• Very low blood pressure
• Where gas exchange takes place. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood.

Outline the passage of oxygenated and deoxygenated blood through the heart and body (including the chambers of the heart and the major arteries and veins)

The passage of blood through the heart:

Deoxygenated blood arrives at the left-hand side of the heart:

1. It enters the heart through the vena cava.

2. Blood flows into the right atrium.

3. Blood is pumped into the right ventricle.

4. Blood is pumped out of the heart, along the pulmonary artery, to the lungs.

Oxygenated blood arrives at the right-hand side of the heart:

1. It enters the heart through the pulmonary vein.
   
2. Blood flows into the left atrium.
3. Blood is pumped into the left ventricle.
4. Blood is pumped out of the heart, along the aorta, to the rest of the body.

Chambers of the heart:

The heart is divided into four chambers. 

• The upper two, the atria (articles) are thin walled and receive blood from the body (right) and lungs (left).
• The lower two, the ventricles have thick muscular walls and pump blood away (the left to the body, the right to the lungs).

The Atria (singular= atrium)

• These are 'holding chambers' for blood which enters the heart- they have thin walls made for cardiac  muscle.
• The right atrium recieves deoxygenated blood from the body. Once its full, a valve into it closes, and a valve opens to let blood into the right ventricle.
• The left atrium recieves oxygenated blood from the lungs. When it is full, blood is propelled from it into the left ventricle. 

The ventricles

• The ventricles are larger, thicker walled chambers than the atria which pump blood away from the right
• The right ventricle has a thinner wall and pumps deoxygenated blood to the lungs.
• Th left ventricle has a thick muscular wall and pumps oxygenated blood to the rest of the body via a large artery called the aorta.

LO:To identify the main cerebral arteries (anterior, middle, posterior) and the regions of the cortex they supply. 

Cerebral arteries: 

Cerebral arteries:                                

• Anterior- region supplied: motor cortex (pre-frontal & supplementary and part of primary) and sensory cortex (part of primary)
• Middle-  Sensory cortex, Motor cortex, Broca’s area, Wernicke’s area
• Posterior- Occipital lobe, inferior part of the temporal lobe,  various deep structures including the thalamus and the posterior limb of the internal capsule.

LO: To identify the function of the circle of willis. To identify the cerebral arteries that are its constituents.

Circle of Willis: The arteries at the base of the brain are set out in a circle called the Circle of Willis. This is a series of anastomoses (points of communication between arteries,) that encircles the optic chasm.

Function: This set up ensures that even if one artery to the brain becomes block, oxygenated blood will still reach it via the other arteries. It also helps equalize locally high and low blood pressure and promotes equal distribution of blood.

Arteries:It is made up of 5 major arteries, some of which cover both the left and the right sides of the brain. These arteries are:

•  Anterior Communicating Artery
•  Anterior Cerebral Artery (left and right)
•  Internal Carotid Artery (left and right)
•  Posterior Communicating Artery (left and right)
•  Posterior Cerebral Artery (left and right)

The Cerebral Arteries supply the brain with oxygenated blood. As they supply different cortical regions of the brain damage to different arteries causes different impairments. Also means that if one artery is blocked there are alternative pathways.

• Language impairments are most likely to be caused by damage to the MIDDLE CEREBRAL ARTERY (MCA) in the left hemisphere.