The Digestive System

The Digestive system is the mechanical and chemical break down of food in the body in order to harvest nutrients and the energy that is contained within the food.
In layman's terms, It is a large tube that runs through the body, food goes in, nutrients are absorbed, and waste (feces) comes out.
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The Mouth.

Mechanical Digestion begins in the mouth. Our teeth are what we use to break down foods into smaller pieces so that it may pass through the esophagus this is known as mastication. Average adult humans have 32 teeth while newborns have 20. The hard palate forms the front roof of the mouth while the soft palate forms posterior roof of the mouth. While the food is in the mouth it is exposed to a digestive liquid known as saliva. Saliva is the first type of chemical digestion that the food will encounter in the body. Saliva will begin to break down the food and lubricate it so that it may pass down the esophagus. Food that is passing down the esophagus is known as chyme.
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The Esophagus.

The esophagus is what allows food to travel through the body to reach the stomach. The esophagus is about 10 inches long.
For the chyme to pass through the esophagus, a phenomenon known as peristalsis must occur. Peristalsis is the action of the muscles in the esophagus contracting and expanding to allow chyme to travel down to the stomach. The chyme will reach the cardioesophageal sphincter and be admitted into the stomach.

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The Stomach.

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The stomach is C-shaped and is on the left side of the body. When the bolus enters the stomach through the cardiac sphincter it falls into gastric acid and pepsin, both of which begin to break down the food even further.

The Small Intestine.

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The bolus leaves the stomach and enters the small intestine. The small intestine is where all the nutrient absorption occurs. It is longer than the large intestine but smaller in diameter than the large intestine.

The Large Intestine.

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After the bolus leaves the small intestine through the ileum it enters the large intestine and will be transferred through the colon out the rectum and finally exit the body as feces.

The Endocrine System

The endocrine system is how our body regulates our body in homeostasis through the use of hormones that are sent from certain glands of the body to other parts of the body or other glands.

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Pituitary Gland

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The pituitary gland is one of the major endocrine glands in the human body. The pituitary gland is found in the "Turk's Saddle" of the sphenoid bone. There are two lobes to the pituitary gland, an anterior and posterior. It produces several hormones:
Growth Hormone which promotes growth of the body skeletal muscles and bones.
Prolactin is a hormone that who's purpose is to have mother's lactate after childbirth.
Thyroid Stimulating hormone is a hormone that stimulates the activity and growth of the Thyroid Gland.
Adrenocorticotropic hormone is what regulates the endocrine activity of the cortex portion of the adrenal gland.
Antidiuretic Hormone causes the kidneys to reabsorb more water from the forming urine; as a result, urine volume decreases and blood volume increases.


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The Hypothalamus is what controls the pituitary gland, it can also produce two additional hormones which are released by the posterior pituitary gland.

Pineal Gland

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Found in the roof of the third ventricle of the brain; it produces the hormone melatonin. Melatonin makes us drowsy which is basically sleep trigger that establishes the body's day and night cycle.

Thyroid Gland (Parathyroid)

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The thyroid gland is located below the adams apple. The thyroid gland prodces the hormones Thyroxine (T4) and Triiodothronine T3), these hormones stimulate metabolism.

Adrenal Glands

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Adrenal Medulla

Produces the hormones Epinephrine (Adrenaline) and norepinephrine (Noradrenaline), these hormones raise blood glucose levels, increase the rate of metabolism and can constrict certain blood vessels.

Adrenal Cortex

Produces Glucocorticoids which increase blood glucose
Mineralocorticoids which promote reabsorption of NA+ and execretion of K+ in kidneys


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The Pancreas produces the hormones: Insulin- Reduces blood glucose
Glucagon- Raises blood glucose

Gonads (Ovaries and Testicles)

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Our reproductive system is what keeps the humans species from dying out and becoming extinct.

The Skeletal System

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Our skeletal system is what provides the framework and protection for our body. Without our skeletal system we would just be blobs of skin and organ lying on the floor. We have long bones, short bones, flat bones, and irregular bones. There are 206 bones in the human adult body. There are two basic types of bone tissue, Compact bone and Spongy bone. Our skeletal system is made up of several parts, joints, cartilages, and ligaments are all parts of what makes up our skeletal system.


Our bones are for several important body functions:

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    • They form the internal framework that supports and anchors all soft organs.
  2. Protection
    • The protection of soft body organs, the rib cage protects the heart and lungs while the skulls protects the brain.
  3. Movement
    • Skeletal muscles which are attached to bones by tendons, use the bones as levers to walk, run, and swim.
  4. Storage
    • Fat, along with, calcium can be stored in the bones.
  5. Blood Cell Formation
    • Blood cells are formed in the bones.

Our bones are made up of calcium, phosphorus, sodium, and other minerals. Bones are the sites of red blood cell production.

  • The outer surface of bone is the periosteum. It's contains nerves and blood vessels that nourish the bone.
  • The next layer is made up of compact bone.
    • Within the compact bone are many layers of cancellous bone, which looks a bit like a sponge.
  • In many bones, the cancellous bone protects the innermost part of the bone, the bone marrow. Bone marrow is the site of red blood cell production.

The Human Skull

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The skull is one of the most important collection of bones inside our body. The skull protects our brain from any sort of damage and trauma that may hit our heads. There are 29 bones in the skull. Which are found in two sets of bones, the Cranium and the Facial bones
  • Cranium- Encloses and protects the fragile brain tissue
  • Facial Bones- Hold the eyes in an anterior position and allow the facial muscles to show our feelings through smiles and frowns.
  • Sutures- Interlocking immovable joints

The Spine

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Our spines are what keep our bodies upright and erect so that we may be able to perform daily activities. There are 30 bones in our spine. Our spinal cord also acts as an essential pathway for our nervous system to operate (but that's a story for another time). The Spinal cord is divided into 4 sections:
  • Cervical Region- Seven cervical Vertebrae (C1-C7)
  • Thoracic Region- Twelve Thoracic Vertebrae (T1-T12)
  • Lumbar Region- Five Lumbar Vertebrae (L1-L5)
  • Sacrum/Coccyx Region- Fused bones at the end of the spine.

Primary curvatures are spinal curves that are present when we are born, secondary curvatures develop through growth.

Abnormal Spinal curvatures include:
  • Scoliosis
  • Kyphosis
  • Lordosis
All of which include abnormal curves in the spine
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The Rib Cage

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The rib cage is what protects the the heart and the lungs which are located in the chest. There are 12 pairs of ribs all of which curve downward and articulate with the vertebral column posterior.
  • True Ribs- The first Seven pairs of ribs attach to the sternum through coastal cartilages.
  • False Ribs- Next five pairs of ribs that attach indirectly to the sternum through cartilage
  • Floating Ribs- The last two pairs of ribs that do not connect to the sternum.

The Tibia/Fibula

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Bones of the lower legs, there are two main bones both which are joined by the interosseous membrane. These bones are what help us move around and participate in sports. It is located just under the patella or knee bone.

The Radius/Ulna

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The Bones that make up the arm, similar to the Tibia/Fibula construction. Unlike the Tibia/Fibula the Radius/Ulna combo can rotate with the assistance of the Trochlear notch, it helps us rotate objects for use such as being able to choose a spot on where to bite an apple.

Hands and Feet

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Our hands and feet are what we use to move around and pick up objects, both are made up of three subunits, carpals, tarsals, metacarpals, metatarsals, and the phalanges.


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Humans use muscles everyday in their lives, they help us move, lift, and operate organs in our body. Without our muscles we would just be a bag of bones that wouldn't be able to move at all.

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Abdominal Muscle
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