1 a)The unique characteristic of a synovial joint is the presence of a space called a synovial cavity between the two (or more) articulating.
The synovial cavity allows a joint to be freely movable; hence all synovial joints are classified functionally as diarthroses.
The bones at a synovial joint are covered by articular cartilage which is called hyaline cartilage.
This cartilage covers the surfaces of the articulating bone with a smooth at slippery surface but does not bind them together. This reduces friction between bones and the joint when movement occurs and helps with shock absorption.
A sleeve-like articular capsule surrounds every synovial joint and encloses the synovial cavity and brings the articulating bones together; this capsule is composed of two layers: an outer fibrous capsule and an inner membrane.
The flexibility of the fibrous capsule permits considerable movement at a joint while its great tensile strength helps to prevent the bone from dislocating.
The synovial fluid: the synovial membrane secretes synovial fluid which covers the surfaces of the articular capsule with a thin film.
Many synovial joints also contain accessory ligaments called extra capsular ligaments intra capsular ligament. Extra capsular ligaments are found outside the articular capsule like the fibular and tibial collateral ligaments of the knee joint. The intra capsular ligaments are found within the articular capsule but are excluded from the synovial cavity by folds of the synovial membrane. Examples are the anterior and posterior cruciate ligaments of the knee.
Inside some synovial joint such as the knee are pads of fibrocartilage that lie between the articular surfaces of the bones and are attached to the fibrous capsule, this pads are called articular discs or menisci.
There are six types of synovial joints:
Planar joint: the surfaces of the bones that articulate in a planar joint are slightly curved or flat. They primarily permit side to side and back and forth movements. Planar joints are sad to be non-axial because the motion they allow does not occur around an axis.
An example of a planar joint is the intercarpal joint between the carpal bones and the wrist.
In a hinge joint the convex surface of one bone fits into the concave surface of another bone. Hinge joints produce an angular opening and closing motion. This joint is monoaxial because they allow motion around a single axis. Examples of this joint are the knee, elbow and the ankle.
The pivot joint: the rounded or pointed surface of one bones articulates with a ring formed partly by another bone and partly by a ligament. This type of joint is monoaxial because it allows rotation around its own longitudinal axis only.
An example of the pivot joint is the atlanto-axial joint, in which the atlas rotates around the axis and permits the head to turn from side to side
A condyloid joint is also called an ellipsoidal joint. This joint is charecterised by the oval shaped projection of one bone that fits into the oval shaped depression of another bone. This type of joint is biaxial because the movement it permits is around two axes, just like the wrist and the metacarpophalangeal joint for the second through 5th digit.
In a saddle joint, the articular surface of one bone is saddle shaped and the articular surface of the other bone fits into the “saddle”.
A saddle joint is a modified condyloid joint in which the movement is somewhat freer.
Saddle joints are biaxial, producing side to side and up and down movements. The carpolmetacarpel joint between the trapezium of the carpus and the metacarpal of the thumb is an example of a saddle joint.
A ball and socket joint consists of the ball-like surface of one bone fitting into a cup-like depression of another bone. The ball and socket joint is multiaxial because it permits movement around three axes plus all directions in between. An example is the shoulder joint where the head of the humerus fits into the glenoid cavity of the scapula.
b) Cartilaginous joints: A cartilaginous joint lacks a synovial cavity and allows little or no movement. The articulating bones in this joint are tightly connected by hyaline cartilage or fibrocartilage.
We can classify cartilaginous joints into two categories:
*Synchondrosis: is a cartilaginous joint in which the connecting material is hyaline cartilage. Functionally a synchondrosis is a synarthrosis. When bone elongation ceases, bone replaces the hyaline cartilage and the synchondrosis becomes a synostosis: a bony joint.
An example of a synchondrosis is the joint between the first rib and the manubrium of the sternum which ossifies during adult life and becomes an immovable synostosis.
*Symphysis is a cartilaginous joint in which the end of the articulating bones are covered with hyaline cartilage, but a broad, flat disc of fibrocartilage connects the bones.
A symphysis is an amphiarthrosis, a slightly movable joint.
All symphyses occur in the midline of the body. For example is the pubic symphysis between the anterior surfaces of the hipbone.
c) Fibrous joints: lack a synovial cavity and the articulating bones are held very closely together by fibrous connective tissue. They permit little or no movement.
There are three types of fibrous joints. Sutures, syndesmoses and gomphoses.
*Syndesmoses: a syndesmosis is a fibrous joint in which there is quite a distance between the articulating bone and the fibrous connective tissue.
The fibrous connective tissue in this joint is arranged in either a bundle meaning a ligament or as a sheet meaning an interosseous membrane.
Because this joint permits slight movement a syndesmosis is a classified functionally as an amphiarthrosis.
An example of this joint is the interosseous membrane between the parallel bordersof the tibia and fibula.
*Gomphoses: A gomphosis or a dentoalveolar is a type of fibrous joint in which a cone shaped peg fits into a socket.
A gomphosis is classified functionally as a synarthrosis, an immovable joint.
The only examples of of gomphoses are the articulations of the roots of the teeth with the sockets of the alveolar processes of the maxillae and mandible.
d)As mentioned in the answer 1c, a suture is classified as a fibrous joint.
This fibrous joint is composed of a thin layer of dense fibrous connective tissue that unites only bones of the skull.
The irregular interlocking edges of sutures gives them added strength and decrease their chance of fracturing. Because a suture is immovable, it is classified functionally as a synarthrosis.
An example of a suture is the coronal suture between the parietal and frontal bone.
Some sutures , eventhough present during childhood are eventually replaced by bone in thye adult. This type of suture is called a synostosis or a bony joint. This means that there is a complete fusion of bone across the suture line. An example is metopic suture between the left and right sides of the frontal bone that begins to fuse during infancy.
The skeleton is the framework of the body, it supports the softer tissues and provides
points of attachment for most skeletal muscles
The human skeleton provides mechanical protection for most of the body’s internal organs,
reducing risk of injury.
For example, cranial bones protect the brain, vertebrae protect the spinal cord, and the
ribcage protects the heart and lungs.
Assisting in Movement
Our muscles are attached to our bones, so when contraction occurs, the muscles cause our bones to move.
Storage of Minerals
Bone tissues store minerals like calcium (Ca) and phosphorus (P). When
required, a release of minerals into the blood stream occurs facilitating the balance of minerals in the body.
Production of Blood Cells
The red bone marrow inside some larger bones (including, for example, the ….) blood
cells are produced.
(Red Blood Cells, White Blood Cells and Platelets are described on the page: Structure &
Functions of Blood.)
With increasing age, some bone marrow changes from being red bone marrow to yellow bone marrow.
Yellow bone marrow consists mainly of adipose cells and a few blood cells. It represents an important energy reserve.
3) The bones in our bodies can be classified into five main types based on their shape: long, short, flat, irregular and sesamoid.
Long bones have greater length than width and consist of a shaft and a number of extremities.
They are normally a bit curved for strength because when a bone is curved it absorbs the stress of the body at several different points, so it becomes evenly distributed.
If these bones were straight, the weight of the body wouldn’t be evenly distributed and the bone would be prone to injury.
These long bones consist mostly of compact bone tissue in their diaphysis but they also contain considerable amounts of spongy bone tissue in their epiphyses.
Long bones include those in the thigh (femur), leg (tibia and fibula), arm (humerus)â€¦
Short bones are cube shaped because their width and length are nearly equal. They consist entirely of spongy bone except at the surface, where a thin layer of compact bone tissue is to be found.
Examples of short bone are the wrist or carpal bones except for the pisiform which is classified as a sesamoid bone and the ankle and tarsal bones except for the calcaneus which is classified as an irregular bone.
Flat bones are normally composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue and are generally thin.
Flat bones protect our internal organs and provide extensive areas for muscle attachment. Flat bones include the cranial bones, which protect the brain. The sternum and ribs protect organs in the thorax and the scapulae.
Irregular bones cannot be classifies as short, long or flat bones. They have complex shapes and they vary in the amount of spongy and compact bone present. Examples are the vertebrae and some facial bones.
Sesamoid bones are shaped like sesame seeds. They develop in certain tendons where there is considerable friction, physical stress and tension. These places are the palms and soles.
Each person is different so they may vary from person to person, and they do not always ossify and they typically only measure a few millimetres in diameter.
The exceptions are the two patellae which are normally present in everybody and are quite large..
Functionally, the sesamoid bones protect tendons from excessive wear and tear, and they often change the direction of pull of a tendon.
4) When a long bone first starts developing, it starts off as cartilage which then hardened into
bone by a process called ossification. We can divide the process of ossification into two main
During the first ossification phase, a layer of cells called Osteoblasts covers the cartilage, which then form other bone cells. Once this encasement of osteoblasts has formed, the cartilage is slowly replaced by cartilage.
The bone cells are arranged in concentric circles causing the bone to become very hard. The mature cells, called osteocytes, store the calcium of the body which can be released or
extracted from the bloodstream depending on the body’s needs. After the bone formationis completed, the mature bone is encased in a membrane of connective tissue called the
Growth takes place at the epiphyseal growth plate of long bones by a finely balanced
cycle of cartilage growth, matrix formation and calcification of cartilage that acts as a
scaffold for bone formation. This sequence of cellular events constitutes endochondral
ossification. Another feature of bone growth is the process of modelling, where bone is
being continuously resorbed and replaced by new bone. Modelling is most active during
childhood and adolescence, and enables long bones to increase in diameter, to change
shape and develop a marrow cavity. Modelling continues throughout adult life with bone
resorption equally balanced by bone formation in a healthy skeleton, although in the adult
the process is referred to as remodelling. An individual’s skeletal growth rate and adult
limb bone length have an important genetic determinant, but are influenced by many
factors including circulating hormones, nutritional intake, mechanical influences and
disease. Growth disturbances result when there is disruption of the normal cellular activity
of growth plate chondrocytes and/or the cells of bone. [online] http://library.thinkquest.org/3007/skeletal.html
5) There are four steps in the process of healing a simple fracture of a long bone.
*Fracture hematoma: The blood vessels crossing the fracture line are broken due to the fracture. These vessels include the ones in the periosteum, osteons, medullary cavity and the perforating canals. The blood leaking from the vessel-ends eventually forms a clot around the site of fracture. This is called a fracture hematoma, which normally forms from 6 to 8 hours after the injury.
The bone cells that are close to the fracture die off because the blood circulation at the site stops.
In response to the dead bone cells, swelling and inflammation occur, producing additional cellular debris. The damaged and dead tissue around the fracture hematoma is removed by the osteoclast and phagocytes. This stage could take seven weeks.
*The formation of fibrocartilaginous callus: The presence of the new capillaries in the fracture hematoma helps organize it into a growing connective tissue called procallus.
This procallus in invaded by fibroblasts from the periosteum and osteogenic cells from the periosteum, endosteum and the red bone marrow.
These fibroblasts produce collagen fibers that help connect the broken ends of the bone, meanwhile the phagocytes continue to remove the cellular debris. The osteogenic cells develop into chondroblasts and begin to produce fibrocartilage. The procallus is transformed into a fibrocartilaginous callus which bridges the broken ends of the bone. The formation of the fibrocartilaginous callus takes about 3 weeks.
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*The formation of bony callus: in areas where healthy bone tissue is found, osteogenic cells develop into osteoblasts that produce spongy bone trabaculae. After a period of time, the fibrocartilage changes into spongy bone and the callus becomes the bony callus. The bony callus lasts about 3 to 4 months.
*Bone remodelling: this is the final phase of fracture repair. The osteoclasts slowly absorb the dead remains of the original fragment of the broken bone. The spongy bone is then replaced by compact bone around the periphery of the fracture. Sometimes a thick area on the surface of the bone remains as evidence of a healed fracture and a healed bone may be stronger than it was before the break. And sometimes the repair process is so thorough that the break line may be undetectable.
Even though bone has a good blood supply, healing fractures sometimes can take months.
The calcium and phosphorus that is needed to strengthen and harden new bone is deposited only gradually and bone cells generally grow and reproduce slowly.
The temporary disruption in its blood supply helps explain the slowness of the healing.
6)Skeletal muscle: is named for its location which is attached to the bones of the skeleton, and because most skeletal muscles function to move bones of the skeleton.
Skeletal muscle tissue is striated: alternating light and dark bands are seen when observed by a microscope.
Skeletal muscle tissue works mostly voluntarily. Its activity can be controlled by neurons that are part of the somatic division of the nervous system. Most skeletal muscles are also controlled subconsciously to some extent. For example the diaphragm continues to contract while sleeping and the skeletal muscles responsible for our posture and for stabilizing our body positions continue to contract unconsciously.
The functions of skeletal muscles: -they function in pairs to bring about the co-ordinated movements of the hips, legs, armsâ€¦and they are said to be directly involved in the breathing process.
Only the heart contains cardiac muscle tissue, which forms most of the heart wall. Cardiac muscle is also striated but its action in involuntary. The contraction and relaxation of the heart is not consciously controlled.
The reason why the heart beats is because it has a pacemaker that initiates each contraction. This intrinsic rhythm is called autorhythmicity. Heart rate is controlled by neurones and neurotransmitters that speed up or slow down the pacemaker.
-Cardiac muscle tissue plays the most important role in the contraction of the atria and ventricles of the heart.
-It causes the rhythmical beating of the heart, circulating the blood and its contents throughout the body as a consequence.
Smooth muscle tissue is found in the walls of hollow internal structures, like blood vessels, airways and most organs in the abdominopelvic cavity.
It can be found in the skin, attached to the hair follicles. Under the microscope, the tissue lacks striations of the skeletal and the cardiac muscle tissue. This is why it looks smooth.
The action of smooth muscle is usually involuntary. Both cardiac and smooth muscle tissue are regulated by neurons that are part of the autonomic division of the nervous and by the hormones released by the endocrine glands.
– Smooth muscle controls involuntary and slow movements like the contraction of the smooth muscle tissue in the walls of the stomach and intestines.
-The muscle of the arteries contracts and relaxes to regulate the blood pressure and the blood flow.
8) There are two kinds of digestion: mechanical and chemical.
Mechanical digestion is the process of chewing, mashing, and breaking food into smaller pieces. Chemical digestion is the process of enzymes breaking the food into simpler substances. Enzymes are proteins that speed up the chemical breakdown of complex substances. The chief system movements are peristalsis that is process that involves carrying food through the tube and the dividing movement, which breaks up the food particles.
Mechanical Digestion happens in the mouth. The saliva, teeth, and tongue all play an important role in the mechanical digestion this process.
Any taste or smell of food sends signals to the brain. The brain in turn sends messages to a system of salivary glands. Saliva is mostly made up of water. It starts to soften up the food so it can pass more down the throat easily. There is also an enzyme named ptyalin which breaks down the food.
The teeth chop the food by a series of actions such as clamping, slashing, piercing, grinding and crushing. The teeth are the first components of the digestive system that break up food.
The tongue is a very manoeuvrable and pliable arrangement of muscle. It removes, and dislocates food particles in the teeth and moves it around in the mouth in order to help with of swallowing. At this stage, swallowing the food is called a bolus. When the tongue presses up against the hard palate , the food is forced to the back of the mouth. This action brings the soft palate and ursula into action which keep the food from heading toward the nose.
Once past the soft palate, the food is in the pharynx. Here there are two pathways. One that leads to the trachea and the other to the oesophagus . The epiglottis helps with movement of air as it is swallowed and equally restricts entrance to the esophagus. The larynx, provides the epiglottis with most of its muscle for movement. It applies an upward force that helps to relax some tension on the esophagus.
About 10 inches down the esophagus, the swallowed bolus is quite different from the state it started out in. The function of the stomach is best described as a food processing and a storage cistern. When the stomach is full it becomes about a foot long and six inches wide able to hold about two quarts of food and drink. The stomach is both chemical and mechanical. Various chemicals in the stomach interact to break down the food like the digestive enzymes pepsin, rennin, and lipase. The hydrochloric acid creates a suitable environment for the enzymes and also assists in the digestion. Also, watery mucus provide a protective lining for the muscular walls of the stomach so it will not be digested by the acid or enzymes. The mechanical action of the muscles in the stomach constrict and relax in a continuous motion which turn the food into chime so it can then be passed on to the small intestine.
It is the longest organ of the digestive tract. Its three sections are: the duodenum, the jejunum, and the ilium.
The food has reached a stage where it has been diminished to very small molecules that are able to be absorbed through the intestinal walls into the bloodstream.
Carbohydrates are broken down into simpler sugars like proteins to amino acids; and fats to fatty acids and glycerol. The walls of the duodenum secrete enzymes and unite with the bile and pancreatic enzymes in the duodenum.
Peristalsis pushes the liquid out of the duodenum into the jejunum. A huge number of villi , microscopic, hair like structures, begin to absorb the amino acids , sugars, fatty acids and glycerol from the digested contents of the small intestine.
This is the place which is about a third of the small intestine. The greatest number of the estimated five or six million villi in the small intestine are found along the ilium making it the main absorption location of the gastrointestinal tract. The villi here are always in moving: oscillating, pulsating, lengthening, shortening, growing narrower then wider, extorting every particle of nutrient.
The Liver, Gallbladder, and Pancreas
These three organs lie outside of the gastrointestinal tract. But the digestive fluids from all three meet at the bile duct. Their movement into the duodenum is controlled by a sphincter muscle. The pancreas produces digestive enzymes. The gallbladder acts as a small reservoir for bile. The liver reproduces nutrients so that they can be used for cell-rebuilding and energy.
Any solid substance that flows into the large intestine through the ileocecal valve is said to be indigestible, or they are bile constituents. The water is taken in by the cecum.
The large intestine acts as a provisional reservoir for water. There are no villi in the large intestine. Peristalsis is much less forceful than in the small intestine. When the water is absorbed, the contents of the large intestine switch from a watery liquid and are compressed into semisolid feces.
The fecal material moves through the colon down to the several remaining inches known as the rectum after . Then they are expelled through the anus which is controlled by the outlet valves of the large intestine.
Site of Enzyme Origin
Nutrient It Breacks Down
Product Of Enzyme Action
Place of Enzyme Action
Maltase, Lactase, Sucrase
Trypsin, Lipase, Amylase
Proteins, Fats/Lipids, Carbohydrates
Amino acids, Glycerol/Fatty Acids, Simple Sugars
In humans, the gastrointestinal tract is a long tube with muscular walls comprising four different layers: inner mucosa, submucosa, muscularis externa, and the serosa (see histology section). It is the contraction of the various types of muscles in the tract that propel the food.
The GI tract can be divided into an upper and a lower tract. The upper GI tract consists of the mouth, pharynx, esophagus, and stomach. The lower GI tract is made up of the intestines and the anus.
Upper gastrointestinal tract
The upper GI tract consists of the mouth, pharynx, esophagus, and stomach.
The mouth comprises the oral mucosa, buccal mucosa, tongue, teeth, and openings of the salivary glands. The mouth is the point of entry of the food into the GI tract and the site where digestion begins as food is broken down and moistened in preparation for further transit through the GI tract.
Behind the mouth lies the pharynx, which leads to a hollow muscular tube called the esophagus or gullet. In an adult human, the esophagus (also spelled oesphagus) is about one inch in diameter and can range in length from 10-14 inches (NR 2007).
Food is propelled down through the esophagus to the stomach by the mechanism of peristalsis-coordinated periodic contractions of muscles in the wall of the esophagus. The esophagus extends through the chest and pierces the diaphragm to reach the stomach, which can hold between 2-3 liters of material in an adult human. Food typically remains in the stomach for two to three hours.
The stomach, in turn, leads to the small intestine.
The upper GI tract roughly corresponds to the derivatives of the foregut, with the exception of the first part of the duodenum (see below for more details.)
Lower gastrointestinal tract
The lower GI tract comprises the intestines and anus.
Bowel or intestine
The small intestine, approximately 7 meters (23 feet) feet long and 3.8 centimeters (1.5 inches) in diameter, has three parts (duodenum, jejunum, and ileum). It is where most digestion takes place. Accessory organs, such as the liver and pancreas help the small intestine digest, and more importantly, absorb important nutrients needed by the body. Digestion is for the most part completed in the small intestine, and whatever remains of the bolus have not been digested are passed onto the large intestine for final absorption and excretion.
duodenum – the first 25 centimeters (9.84 inches)
jejunum and ileum – combined are approximately 6 meters (19.7 feet) in length
The large intestine – (about 1.5 meters (5 feet) long with a diameter of about 9 centimeters (3.5 inches) also has three parts:
cecum (the appendix is attached to the cecum)
The colon (ascending colon, transverse colon, descending colon and sigmoid flexure) is where feces are formed after absorption is completed
The rectum propels feces to the final part of the GI tract, the anus
The anus, which is under voluntary control, releases waste from the body through the defecation process
10) The ATP-PC System: The ATP-PC system does not use oxygen or produces lactic acid.It is said to be alactic anaerobic if there is no oxygen. This system is used for outbursting sporting events like a 100m run, so it is used from 10 to 15 seconds only. After this, more systems kick in to supply the muscles with energy.
The Anaerobic System or the lactic acid system: this system is used for exercises that last for less than 2 minutes. It is Also known as the Glycolytic System. This type of energy source would be used in a 400m sprint.
The Aerobic System: This is known as the energy system for long duration activities. After 5 minutes of exercise the Oxygen system takes over. For example in a 2km run, the oxygen system provides about half the energy and in a marathon run it provides about 98% of the energy.
the rate at which blood flows through the tissues can determine the rate at which lactic acid leaves the muscle and enters the blood stream. The heart and other skeletal muscles can take the lactic acid and convert it back into pyruvic acid and then can metabolize it to turn it into ATP to generate energy. If some of the lactic acid is not used this way, in the period straight after exercise, it will be converted back into glycogen by the liver.
After exercise, or between repetitions during interval training, we can use active or a passive recovery. An active recovery involves exercising at a low intensity and the passive mode means total rest after exercise.
During exercise if lactic acid is accumulated, it is better to use an active recovery because of the good blood flow, and in this way, the lactic acid dispersal from the muscle will greater than during one with a passive recovery. The rate at which lactic acid is used as an energy source by the heart and skeletal muscle will be greater during low intensity exercise than that at rest.
The best exercise intensity for an active recovery depends on a persons’ fitness level, but generally for most people it occurs at heart rates of approximately 15-30 beats per minute below that of the anaerobic threshold.
It may take as long as 30 minutes, with an active recovery, for 95% of the accumulated lactic acid to be removed after extremely intense anaerobic exercise. But the levels of lactic acid may remain elevated above resting levels for about 60 minutes or more if a passive recovery is used.
Lactic acid levels do drop quite significantly in the first few minutes of recovery and could take as little as five minutes of active recovery for 50% of the accumulated lactic acid to be removed from the blood stream. So, a significant recovery will occur when five to 10 minutes are taken between intervals.
12) The definition of muscle fatigue: “Muscle fatigue is the temporary reduction in muscle strength, either power or endurance. Muscle fatigue coincides with a build up of lactic acid in the cells of the muscle. Recovery is not complete until the lactic acid is processed through the system.” 9muscle fatigue definition online) http://ergonomics.about.com/od/glossary/g/muscle_fatigue.htm
Muscle fatigue mainly results from changes in the muscle fibres. Sometimes, even before muscle fatigue occurs during exercise, a person might get a feeling to want to stop exercising. This is called central fatigue, and it is a protective mechanism to stop the person before their muscles become too damaged. Some certain types of muscle fibres fatigue quicker than others.
Eventhough, we are not sure of the precise mechanisms that cause
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