Seedlings of the coffee
plant have a high concentration of caffeine. The high concentration is toxic and protects the seedlings from insects that want to snack on it.
Toxic caffeine levels also have another interesting defense mechanism. It prevents the germination of any other
plants in the area. This is referred to as
allelopathy. In
humans, caffeine has also been thought to reduce the risk of diabetes and heart disease in addition to helping us face long days of work and school.
TERPENOIDS
Terpenoids are made of isoprene units and are found in all
plants. They are the largest group of secondary metabolites and are very volatile, which means they evaporate easily.
Isoprene is a gas produced in the chloroplasts and released by the leaves. Isoprene is thought to protect the
plant from heat.
Essential oils give
plants their fragrance. In some
plants, the scent is used to deter
herbivores and protect the
plant from dangerous
pathogens. We use essential oils for aromatherapy and medicine. In aromatherapy, essential oils are thought to improve the mood and mental
functioning. In alternative medicine, essential oils are thought to have quite a few benefits.
Most of the time, essential oils are dangerous if consumed so they are usually applied topically or inhaled. They can be used for skin issues, respiratory ailments and as antiseptics.
European Yew
Branch with Red Fruits
Next is taxol, which has become important in the medical field. It is used to treat ovarian and breast cancer. Taxol comes from the bark of the Pacific yew tree. The bark produced very small amounts of taxol and the process killed the tree. Other sources needed to be found.
Now, other sources of taxol include a
fungusthat grows on the tree and needles of the European yew.
The final type of terpenoid is the one that is the most familiar to us: rubber. It is the largest of the terpenoids because it contains over 400 isoprene units. Rubber is obtained from latex, which is a fluid produced by Hevea brasilenis. The uses for rubber are numerous and go back hundreds of years. Today, we use rubber in shoes, erasers, tires, gloves, spandex and the beloved rubber ducky.
PHENOLS
The final type of secondary metabolites has recently become very popular due to their health benefits: the phenols.
The phenols consist of a
hydroxyl group (–OH) attached to an aromatic ring. Phenols are found in nearly all parts of the
plant and in nearly every
plant on the planet.
The first group of phenols is the
flavonoids. Flavonoids are
water-
soluble pigments found in the
vacuoles of
plant cells. Flavonoids can be further divided into three groups: anthocyanins, flavones and flavnols.
Anthocyanins range in color from red to blue and purple. The color depends on the pH of the environment. Anthocyanins are most commonly found in grapes, berries and have a wide range of health benefits. Anthocyanins are believed to protect against heart disease, diabetes and even cancer when they are consumed. They are also appearing in skincare products to slow down the aging process.
The next two groups have white or yellow pigments. They are called
flavones and
flavnols. As a group, the phenols attract pollinators to the
plants and even impact how
plants act with one another.
Aspirin Tablets
Yet another medically relative phenol is salicylic acid, which is the active ingredient in aspirin. It comes from the bark of the willow tree. It has been used to effectively treat aches and fevers since the days of Hippocrates. It also has cosmetic uses.
It is used in numerous skincare products to treat acne, large pores and dermatitis.The final type of phenol is important to the structure of the
plant and is called
lignin. It adds stiffness and strength to
cell walls of the
plant cells. Lignin is crucial to terrestrial
plants because it supports the
branches and size. It also allows the
cell wall to be
waterproof and protects the
plant from fungal attacks.
Not only do the secondary metabolites have
functions for the
plants, they have proven to be pretty beneficial for us, too. Their effects have not only been cultivated in recent years, but for centuries. Be sure to eat your berries for their great health benefits, and remember where the active ingredient in that aspirin you took came from.
FUNCTIONAL ANATOMY OF THE KNEE: MOVEMENT AND STABILITY
The
knee is a
joint formed, stabilized and given mobility by the articulation of bones,
ligaments and tendons. This
joint is the largest
joint in the body and is formed by the articulation of the femur bone in the thigh with the tibia in the lower
leg.
There are 3 main types of
joints:
Fibrous – an immovable
joint,
Cartilagenous – partially moveable, and
Synovial – a freely moveable
joint. The
knee joint is classified as a synovial
joint for obvious reasons
based on the definitions given.
Synovial
joints or
diarthroses are considered moveable
joints. According to the Encyclopedia of Nursing and Allied Health,
joint function, synovial
joints can be further divided into 3 types, these are:
Uniaxial –
joints that hinge or pivot moving only in one plane,
Biaxial – such as the saddle and condyloid
joints. These
joints move in two planes. And lastly, the
Triaxial – which allows movement in three planes including the ball and socket
joints and gliding
joints
The
knee falls under the uniaxial as it is a hinge
joint and it moves in one plane with slight rotational movement, but the rotation is not enough to be considered significant.
ANATOMY & PHYSIOLOGY
The
knee is the largest
joint of the body and is often the site of pain and injury in athletes (the reason I am writing about this is that I strained my medial collateral
ligament, more on that later), consists of the medial and
lateral condyles (round projection at the end of the bone) of the lower femur (thigh bone) and the same condyles at the upper end of the tibia.
The
patella (
knee cap) covers the front of the
joint, it is the protruding structure you see when you extend your
knee. This structure slides along a groove on the femur.
Each of the 3 bones in the
knee joint are covered with articular
cartilage, which is a tough elastic material, that acts as shock absorbers and allows the
knee joint to move with ease. Another
cartilage tissue called the menisci separates the femur and tibia, divided into two crescent shaped discs located medially and
laterally (inner and outer respectively). This
cartilage also acts as shock absorbers, as well as enhancing stability.
In a normal
knee joint, a
synovium (synovial
membrane) surrounds the
knee jointand it produces synovial fluid that nourishes the surrounding
cartilage in the
knee. The synovium also
functions in protecting and supporting the
joint due to its tough outer layer.
STABILITY
The stability of the
knee is due mainly to four
ligaments. A
ligament is several large fibrous bands of
tissue, comparable to that of a rope, they support the
knee on both sides and front to back.
Ligaments connect bone to bone.
The
ligaments that connect the femur to the tibia and
fibula are as follows:
- Medial Collateral Ligament (MCL), also known as the Tibial Collateral Ligamentbecause it connects the Femur and Tibia, provides stability to the inner (medial) aspect of the knee.
- Lateral Collateral Ligament (LCL), also known as the Fibular Collateral Ligamentbecause it connects the Femur and Fibula, provides stability to the outer (lateral) aspect of the knee
- Anterior Cruciate Ligament (ACL), in the center of the knee, limits rotation and forward movement of the Tibia
- Posterior Cruciate Ligament (PCL), also in the center of the knee, and like the ACL secondarily limits rotation, while primarily limits backward movement of the Tibia.
MOVEMENT
Your
knee is a hinge
joint like your
elbow, which we discussed already, which means it bends and straightens. We also said that it has the ability to slightly rotate as it moves.
The
muscles in the thigh, the
quadriceps and hamstrings perform movement of the
knee joint, but these
muscles need assistance from tendons to connect them to the
muscles. Tendons are tough cords of
tissue that connect
muscle to bone. They are similar to
ligaments in structure. The difference is in just what they articulate with.
When you straighten your
leg, the
quadriceps muscles contract pulling on the
quadriceps tendon, which in turn pulls on the
patella via the
patellar tendon causing an extension of the
knee. Please note the
patellar tendon connects the
patella to the tibia, so technically it is a
ligament, but commonly called a tendon. On the posterior side of the
knee the hamstring group of
muscles contract pulling on the tendons associated with the hamstring, pulling on the femur, which causes the
flexion of the
knee.
LYMPHOPOIESIS: THE DEVELOPMENT OF LYMPHOCYTES
Lymphocytes are the smallest and the second most common type of white blood
cell. They are known as the
cells of
immunity.
Lymphocytes have large
round/oval nuclei that occupies most of the cell with little cytoplasm. The
nucleus will
stain dark purple or blue when it is exposed to a certain stain called Wright’s stain (please see figure 1 ).
There are two types of
lymphocytes T
lymphocytes and B
lymphocytes which the immune response depends upon. They are derived from the hematopoietic stem
cell(HSC).
LYMPHOPOIESIS
The development of lymphocytes begins as the earliest branch from HSC.
As we already know, HSC can develop into common
lymphoid progenitor (CLP) or common myeloid progenitor (CMP). CLP then will
generate T and B
lymphocytes while CMP
generates myeloid elements. So,
lymphocytes
originate from CLP in the bone marrow.
One should note that during postnatal life, the bone marrow and thymus are the
primary lymphoid organs. The secondary lymphoid organs in which specific immune response take place are the
lymph nodes, spleen and lymphoid tissue.
B-LYMPHOCYTE DEVELOPMENT
B-
cells
originate in the bone marrow and circulate the peripheral blood until they recognize an antigen. There are various stages in the development of B
lymphocytes:
- Stem Cell (HSC)
- CLP
- Pro-B cell
- Pre-B cell
- Immature B cell
- Mature B cell
Their development is altered by
cytokines. Interleukin-7 interacts with stem
cellfactor to begin the process. In order for the
cells to
function, they will express on their surface immunoglobulin (Ig).
Ig production begins at the Pro-B
cell stage of B
cell development. Ig is needed for the development and maturation of the B
cell from CLP to pre-B
cell.
The
plasma cells are capable of producing and releasing antibodies, while the
memory cells remember antigens that they were once exposed to in the past.
T-LYMPHOCYTE DEVELOPMENT
T-
Lymphocyte development begins with CLP
cells that migrate to the thymus where they will differentiate into mature T
cells. It is associated with the movement of the
cells through the cortex and medulla of the thymus. Maturing begins in the cortex, and as the
cells develop more they move towards the medulla.
During the developmental stages of T
cells, the
cells contain specific surface
proteins. As the
cell progresses through maturity, they are identified by antibodies that recognize the surface
proteins. In other words, there are
cell surface markers which are used by antibodies to identify the T
cell.
T
cell eventually differentiates into two types of T
lymphocytes: cytotoxic T-
cell and helper T-
cell.
Cytotoxic T-cell is important because they produce a substance called
lymphokines which help B
cells destroy foreign substances. Cytotoxic T-
cells also have
CD8 antigen.
Like B-
cells, T-
cells depend on interleukin-7 and other interleukins. One should note that most of T-
cell development occurs in the thymus; however the final steps in which cytotoxic and helper T-
cell are produced occur in the peripheral blood.
INTRODUCTION TO THE SPINOTHALAMIC TRACT
I think it’s time to make a jump, and to look at the nervous networked that feeds the brain information about what’s going on with the body. There are two types of information relays.
There are pathways that transmit information that goes from the brain to the limbs (called descending tracks), and there are pathways that transmit the information from the limbs to the brain (called the ascending tracks).
But how do you know which track does what?
Ascending and Descending tracts.
Image Credit: Mikael Häggström
LET’S BEGIN WITH THE SPINOTHALAMIC TRACT
First, look at the terminology: Spinothalamic. This gives you a hint as to the direction of the electrical signal. Spino-Thalamic. The information will travel from the spine up to the thalamus (which is situated in the brain). So yes, the spinothalamic tract is an ascending pathway.
At this point you already know that this pathway will have something to do with information about the body.
The spinothalamic tract is involved with perceptions of temperature, itch, touch, and pain.
We also said that the information is being relayed. The term relay applies really well to this situation because the electrical signal will be “relayed” from
neuron to
neuronas it ascends up to the thalamus.
Like most ascending pathways, there are 3
neuronal levels in the spinothalamic tract.
SPINOTHALAMIC TRACT – LEVEL 1
The level 1
neurons are called “
primary neurons.” These primary
neurons have free
nerve endings that will translate pain, temperature, itch, or touch sensations into an electrical signal. These primary
neurons can be pretty long and travel all the way from the bottom of the foot to the spinal cord.
The
cell bodies of these primary
neurons are located in
dorsal root
ganglions.Their axons enter the spinal cord through
Lissauer’s fascicles, then go up one segment before synapsing. They will synapse in the posterior horn on the same side (
ipsilateral side).
SPINOTHALAMIC TRACT – LEVEL 2
The secondary
neurons begin in the posterior horn of the spinal cord (The primary
neurons that we just talked about synapse on them).
At this point, there are two options for these
neurons.
- They can travel up on the same side (ipsilateral ascension)
- Decussate and travel up on the opposite side (contralateral ascension). Most axons will mostly travel up on the contralateral side, but all will synapse in the thalamus (ipsilaterally or contralaterally).
The Contralateral Ascension
It is interesting to note that axons from the lower limbs align themselves on the “
lateral side” of the spinothalamic tract, whereas axons from the upper limbs align themselves more on the “central” side of the spinothalamic tract.
Along the way, some of these
neurons
branch out to the
periaqueductal gray or to the
reticular formation.
That’s pretty cool because pain can be down regulated at these levels. Which means that even if the body sends out a strong pain signal, the brain can actually modulate how much of that pain it will feel…..
Spinothalamic Tract – Level 3
The last level! The tertiary
neurons begin in the
ventral posterolateral
nucleus of the thalamus. Their axons will travel through the
internal capsule. They will keep on going through the corona radiate (I love that name). Their journey will end on the secondary sensory cortex.
REMEMBER THIS:
- The Lateral Spinothalamic tract take pain and temperature info from the body to the brain (ascending).
- This relay system involves 3 neuronal levels.