HUMAN BIOLOGY PART 1
Part One
INTEGUMENTARY SYSTEM
DIGESTIVE SYSTEM
MUSCULOSKELETAL SYSTEM
CARDIOVASCULAR SYSTEM
RESPIRATORY SYSTEM
Part Two
URINARY SYSTEM
NERVOUS SYSTEM
ENDOCRINE SYSTEM
REPRODUCTIVE SYSTEM
INTEGUMENT SYSTEM: Does anyone know what integument means? Integrity? Holding things together? What part of the body do you think this refers to?
- Organs (Skin, Nails, Hair, Glands)
- Functions
- Protection (Abrasions, pathogens, UV light, Dehydration)
- Thermal regulation (maintaining proper body temp)
1)Insulation = adipose layer
2)Cooling = sweat glands
- Sensory reception (touch, temp, pain, etc)
- Vitamin D production
SKIN
- Epidermis
- Dermis
- Hypodermis (fat layer)
SKIN COLOR
Melanin is a substance that is responsible for skin pigmentation (color)
MELANIN: (dark brown pigment made by special cells called melanocytes in the skin). The more melanin you make, the darker the skin.
PROBLEMS WITH SKIN
BURNS: Three types:
FIRST DEGREE: Minor burn to the epidermis; sunburn
SECOND DEGREE: Dermis separates from epidermis; blister
THIRD DEGREE: Hypodermis is burned; this is the most dangerous. Severe burns can get infected and can be deadly because they cause dehydration. 2˚ and 3˚ burns over a large part of the body gives a survival chance proportional to the amount of skin left. 60% burn = 60% chance of dying.Why are deep burns so dangerous?
1) Infection
2) Dehydration: nothing to keep fluid in body.
SKIN CANCER: Three major types:
1) BASAL CELL CARCINOMA:
Cancer of the dermis.
Almost never metastasizes or invades the hypodermis.
Looks like shiny nodules
2) SQUAMOUS CELL CARCINOMA
Cancer of the epidermis.
25% of all cancers
Will metastasize if not treated.
3) MELANOMA
When the melanocytes (that produce the pigment melanin seen in freckles and
moles) divide uncontrollably.
Highly metastatic.
DECUBITUS ULCERS
Epidermis is destroyed from prolonged pressure, underlying tissue is exposed.
How decubitus ulcers form:
If you’re sitting down, weight of the body presses against blood vessels, no blood flow to skin of buttocks. In you, it’s ok, because you’ll be walking around again in a half hour. But if it there is no circulation for longer than a couple of hours because one can’t move, tissues can’t get oxygen. Ulcer forms, can get gangrene or go systemic and die of infection. That’s how Christopher Reeve died.
PSORIASIS: An autoimmune disease of the skin, hereditary; causes flaking skin on knees, elbows, head; not a cancer. No cure.
CONTUSION: “Bruise”
Why does a bruise look black and blue? The vessels in the hypodermis is ruptured, and the blood leaks upward; looks blue. As it gets pushed upwards, it appears green/yellow. The age of the bruise determines the color.
WRINKLES
Over time, collagen fibers align themselves more and more as they are always being pulled in the same direction: smile, frown.
Skin begins to sag because body makes less collagen. Pinch your grandma’s skin. Does it bounce back, or ooze back?
What can be done about wrinkles? Not much. Face lift clips off extra skin.
Creams don’t work. Trying to fix a collagen problem with a cream is like trying to shampoo your carpet by putting the cleaner on the roof!
BOTOX
This is a deadly poison which paralyses the muscles, making them sag. That releases the tension, and relaxes the skin line. In 3 months, new muscle cells are made, so wrinkles come back, and need new injection.
COLLAGEN INJECTION
Collagen is injected into hypodermis. Can last a couple of years.
MOISTURIZER CREAMS
The secret ingredient of all moisturizers is WATER. They work superficially on the epidermis. The top layer of skin is dead, it just hasn’t flaked off yet. Although it is waterproof, it swells when wet. So, if you put a moisturizer on skin, the dead cells on top will expand and hide wrinkles. Get the same effect by soaking in the tub, and that’s cheaper. If you soak in water a long time, it over-swells, and fingers appear deeply wrinkled. Moisturizers work best if you soak in the tub so the natural water gets into the cells, then the cream prevents evaporation. If you wait more than 10 minutes after drying off, the cream doesn’t have much effect because the water has already evaporated. Once the water in the skin evaporates, it takes more water with it, so you’ll wind up with dryer skin if you don’t put moisturizer on it.
TATTOOS
Pigment is injected into the dermis. If the needle is sterile, there’s no health risk.
However, the pigment diffuses with time. What looks good in your 20’s will look like a blob when you’re 50.Laser treatment is just burning the tattoo off all the way to the dermis; leaves scar. I used to laser off a lot of gang tattoos in my last year of medical school at USC. Removing a tattoo will probably leave a scar.
NOSE PIERCING
Let me warn you about nose piercing: There is a region of the face called the “DangerTriangle” which goes from between your eyes to your upper teeth. All of the blood in this region drains into the brain, so infection there can cause meningitis and death in 24-48 hours. A cut on the forehead isn’t so bad, but a cut on the cheek near the nose is considered very dangerous and needs immediate antibiotics. A nose piercing can become a serious infection because some of the worst bacteria in the body is in the nose…that’s why your mother always told you not to pick your nose. Can you imagine if you put a hole in your nose and it got infected? A nose piercing that gets infected can cause meningitis.
WARTS
Warts are caused from a virus that can only get in if there is a break in the skin. It starts multiplying itself, forming a benign local tumor. Therefore they are found on the hands of people who get a lot of scratches and the feet of those who go outside without shoes.
That’s it for the organ called skin; now we’ll move on to the organ called NAILS
NAILS
At the nail root, there is rapid division of skin cells, and as they die, the skin moves up and creates the nail, similar to hair formation. Taking calcium does not make nails stronger because there is no calcium in skin cells.
HAIR There are about 2 million hairs on the body; 200,000 on the scalp.Hair is dead skin cells.HAIR FOLLICLES: If follicle is round, it makes straight hair. If it is oval, makes wavy hair. If it is oblong, makes curly hair.
Laser treatment or electrolysis to remove unwanted hair is a beam that tries to kill the root of the hair. But if the hair is not in the cell division phase, it will not die; that’s why the procedure has to be repeated weekly in an attempt to get the hair while it’s dividing. Also, if the follicle is curved, the beam might not reach the root, and the treatment will never be successful on that hair.
Chemotherapy kills cells which are rapidly dividing (cancer cells), so hairs in follicles die as well as bone marrow cells. That’s why chemotherapy patients are bald.
GLANDS
- SEBACEOUS GLANDS produce sebum, which is OIL that coats the hair and epidermis. IT IS NOT A SWEAT GLAND. It keeps the skin from getting dry and brittle. The problem is that when you wash the oil away, the skin gets dry. Has anyone heard of moisturizers with the ingredient lanolin? It is made from sheep sebum. Some of the largest sebaceous glands are associated with the smallest hairs (face). When they get clogged, the gland swells PIMPLE. In puberty, there is an increase in hormones, and an increase in gland production leading to pimples. A blackhead is sebum which has bound to an oxygen molecule.
- ECCRINE (SWEAT) GLANDS form the sweat when you exercise.
- APOCRINE GLANDS coat the pubic hairs. The hairs function as a wick to draw the secretions to the surface. These glands also produce hormones called PHEROMONES.
Pheromones function to regulate menstrual cycles of females. If you put several women in one room for months, their menstrual cycles will all start to occur at the same time.
Pheromones also function for sexual attraction. There is no conscious odor. The smell from the axilla is from bacteria that are attracted by the gland. Expensive perfumes have pheromones. Guess where they get them from? The anal glands of male cats! They are designed to attract females. They are used so women will buy expensive perfume.
- MAMMARY GLANDS secrete milk.
- CERUMINUS GLANDS are only found in the ear, and they produce wax.
- They keep the ear canal from drying out
- They prevent insects from crawling in; they don’t like walking on the wax.
FUN FACTS ABOUT EPITHELIUM
The 'bone' in a rhinoceros' hornis simply a mass that is not attached to the skull and is made of a protein found in our hair and fingernails called keratin.
At birth, the dolphin arrives into the world with a moustache. But due to a natural depilatory process, within a short period of time the moustache falls off by itself.
The stripes on a tiger are not found just on its coat; the skin of this predator is also striped. But curiously enough, even though the zebra's coat is striped, its skin is not.
THE DIGESTIVE SYSTEM
Also called the gastrointestinal (GI) system
Functions
INGESTION Taking food in by mouth
DIGESTION to break food down into simple molecules
Mechanical: churning of food in the stomach, manipulation of food with tongue, tearing and grinding with teeth.
Chemical: breakdown of food with hydrochloric acid
ABSORPTION nutrients enter capillaries
DEFECATION to eliminate solid waste products
Mouth
Oral Cavity
Hard and Soft Palate
Tongue
Lingual Frenulum
Salivary Glands
Parotid, Submandibular, Sublingual
Teeth
Teeth
When bacteria eat away at the enamel, what’s it called? CAVITY
Bacteria between the gums and the teeth can inflame the gums. This is called GINGIVITIS. This is the major cause of tooth loss. The tooth loosens and falls out. That’s why you need to floss.
FUN FACTS ABOUT THE MOUTH
The enamel in your teeth is the hardest substance in your body.
Your teeth start growing 6 months before you are born.
If you are right handed, you will tend to chew your food on the right side of your mouth. If you are left handed, you will tend to chew your food on the left side of your mouth.
Termites chew up dirt and dung and make massive homes. If they were the size of a human, they could make a home taller than the Empire State Building. They also put in air conditioning systems, covered walkways, stairs and gardens.
Every person has a unique tongue print.
A giraffe’s tongue is 22 inches long
What animal bite causes the most human deaths? Snakes take their toll, but Mosquitoes cause millions of deaths a year. The Komodo dragon has saliva so toxic with bacteria, it just bites it's prey and waits for it to die of infection a few days later.
The average human produces enough spit to fill two swimming pools
GI Tract
This is a tube through the body, forming the esophagus, stomach, small and large intestine. The GI tract functions to digest food and absorb the nutrients.
Esophagus
Stomach
Small Intestine
Large Intestine
STOMACH
Functions:
1. Store Food, so it can be slowly released into a small intestine. Your whole
Thanksgiving dinner can take your stomach diameter from 2” to 8” diameter.
2. Churn food. Secretions from the stomach turns everything gooey, called CHYME.
3. Kill bacteria. The stomach is very acidic (pH 1) like battery acid. Chyme will even
eat through clothing.
4. Some digestion: of proteins.
5. Some absorption: of water, alcohol (alcohol is absorbed in the mouth, too!)
Food takes four hours to completely leave the stomach.
STOMACH ACID
There are gastric pits in the stomach lining. “Gastric” refers to the stomach.
Cells in the gastric pits make acid and digestive enzymes.
There are also lots of goblet cells which make mucus to prevent the stomach from digesting itself. Bacterial infection can erode this area = GASTRIC ULCER.
HEARTBURNis when acid goes from the stomach up into the esophagus (ACID REFLUX). People can take a mild antacid like Tums for relief.
Stomach Cells
CHIEF CELLS secrete an enzyme called pepsinogen. When pepsinogen is exposed to hydrochloric acid (HCl), it is cleaved into pepsin, its active form. Pepsin digests proteins.
PARIETAL CELLS in the stomach secrete hydrochloric acid.
They also secrete intrinsic factor, which is needed to absorb vitamin B12, which is needed to make red blood cells.
Intrinsic Factor
A person who lacks intrinsic factor (such as those who have a stomach stapling procedure or gastric bypass) will not be able to absorb vitamin B12 and they will get a type of anemia called pernicious anemia.
Treatment is injectable B12 shots monthly for the rest of their lives. They also have a new dissolvable sublingual form of vitamin B12
Two major causes of Peptic (stomach and duodenum) Ulcers:
1) 60% of gastric and up to 90% of duodenal ulcers are due to a bacterium called Helicobacter pylori.
The body responds by increasing hydrochloric acid (HCl) secretion, which erodes the stomach lining. 50% of the world’s population has this bacterial infection, especially in underdeveloped countries.
2) NSAIDs (non-steroidal anti-inflammatory drugs, such as aspirin) block prostaglandin synthesis.
Prostaglandins promote the inflammatory reaction. They also are found in the stomach, protecting it from erosion.
The lifetime risk for developing a peptic ulcer is approximately 10%.
In Western countries the prevalence of Helicobacter pylori infections roughly matches age (i.e., 20% at age 20, 30% at age 30, 80% at age 80 etc.).
Prevalence is higher in third world countries.
Transmission is by food, contaminated groundwater, and through human saliva (such as from kissing or sharing toothbrushes or food utensils)
Problems With the Stomach
The cardiac sphincter doesn’t close well, since it is not a true sphincter; consequences:
You can throw up (reverse peristalsis). Rats do have a true cardiac sphincter, and can’t vomit!
That’s why rat poison won’t kill people or dogs; they can throw it up.
Another consequence: hiatal hernia.
FUN FACTS ABOUT THE STOMACH
Astronauts can't belch - there is no gravity to separate liquid from gas in their stomachs.
The Tasmanian Devil can swallow 40 percent of its body weight in a half-hour. That's like eating 216 hamburgers for lunch!
If you ate like a vulture, you could ear 108 hamburgers in one meal. They eat 20% of their body weight. Their stomach acid is so strong they can dissolve botulism and cholera.
Frogs can't vomit, and whenever they need to, they end up vomiting their entire stomach.
SMALL INTESTINE (Small bowels)
These are the longest part of the GI tract (9 feet long, 1” diameter)
The small intestine is the most important region of the GI tract because almost all of the digestion and absorption of food takes place here.
The DUODENUM is the first part of the small intestine. There are two ducts at the beginning of the duodenum from the pancreas and gallbladder.
The main purpose of the small intestine is to absorb nutrients from the food into the bloodstream to be taken to all the cells of the body. After the food passes through the small intestine, it goes to the large intestine.
Problems with Small Intestine
Inguinal Hernias
Crohn’s Disease
Gluten Intolerance
Inguinal Hernia
The inguinal canal is open in the male to allow for passage of the spermatic cord. In the female, the area is closed, but weak.
When there is abdominal pressure (lifting a weight), a piece of small intestine can push out of this canal, causing pain.
Crohn’s Disease
Autoimmune disease of the GI tract
Most common area affected is small intestine
Inflammation causes pain and diarrhea (may be bloody)
Genetic cause (high risk if siblings have it)
Usually occurs in males in their 20’s
No cure; just treatment of symptoms
Gluten Intolerance
Genetic autoimmune disorder of the small intestine, causing chronic diarrhea. The person is allergic to gluten (wheat products). Causes destruction of small intestinal lining.
It is characterized by having pale, loose and greasy stools (steatorrhoea) which are voluminous and malodorous.
It often presents with abdominal pain and cramping, abdominal distension, and sometimes mouth ulcers.
Without adjusting the diet, coeliac disease leads to an increased risk of intestinal cancer.