Digestion- Chen's page

Digestion is an awesome process because Coach said so. external image images?q=tbn:ANd9GcSam3bm2ss3ekhqykxTUSUN_z8j2kDM0R_uS9EVzFaJdw4YKiJRFJ8TftL1external image IMG_0184_bigger.JPG Yes! I will enjoy eating this sandwich!

Digestion describes the process of the breakdown of ingested food and the absorption of the nutrients into the blood. The digestive system consists of multiple organs that make up the alimentary canal, which is a continuous pathway that brings the bolus (chewed and ingested food masses) through the digestive tract.


The organs of the digestive system are categorized into two groups: those that make up the alimentary canal and those who are the accessory digestive organs. The alimentary canal is a long, hollow, and muscular tube that winds through the body. The organs that make up the canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

The accessory digestive organs aid in the digestion process by helping the chewing, breakdown, and storage of food. These organs are the salivary glands (parotid, submandibular, and sublingual), the teeth, the pancreas, the liver, and the gallbladder.

The organs of the alimentary canal are responsible for sending digested food through the digestive tract. The food is taken in in the mouth, which has saliva that helps the food get broken down.
  • The Oral Cavity- Inside the mouth, there is the tongue, which is located on the floor of the mouth, and three salivary glands. These glands are the parotid gland, the submandibular gland, and the sublingual gland. These secrete enzymes such as salivary amylase, which breaks down starches in the mouth. The teeth, which include the incisors, the molars, and the canines. This is what happens when the 32 deciduous teeth are not doing its job. external image images?q=tbn:ANd9GcSKqn7SInTKltKR4oydmA5IdIkc_jzlFB58tIexUMFZcwsBvW1TRW1wrydIhQ
  • The Pharynx- The bolus (mass of chewed food) travels down the pharynx on its way to the esophagus.
  • The Esophagus- When the food enters the esophagus, peristalsis occurs as the throat contracts as it sends the food down through to the stomach.
  • The Stomach- When the food enters the stomach from the diaphragm, the food gets churned into chyme. Hydrochloric acid causes the stomach to become acidic. Gastrin and gastric acid is used to release pepsin, which promotes the release of pepsin. The pepsin is the enzyme that breaks down protein in the stomach. Segmentation occurs where the food is churned and broken up by the movements of the stomach and the cardiesophagial spinchter.
  • The Small Intestine- The small intestine is underneath the pancreas, which creates pancreatic amylase, which helps in the digestion of carbohydrates. The beginning of the small intestine is the duodenum, which connects the pancreas to the small intestine. The hepatic duct The small intestine is made up of the ileum, jejunum, and the cecum. It has an ascending colon, transverse colon, and descending colon. There is also a hepatic flexure and and a splenic flexure. As the chyme travels through the small intestine, the nutrients continue to be digested and absorbed.
  • The large intestine- the large intestine is lake a storage of left over waste. there is a sigmoid colon that leads to the rectum which leads to the anal canal and the anus.

Digesting Carbohydrates, Proteins, and Fat

Different food groups get broken down and digested in different ways in the body. These processes are unique in the body and they allow people to absorb and store nutrients from the digested food. Carbohydrates are the easiest and fastest food type to digest.

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1. Carbohydrates: Starch is broken down by salivary amylase (from the saliva) in the mouth. When it is chewed, it travels through the esophagus and Into the stomach. There, it is worked on by pancreatic amylase. Segmentation occurs, resulting in the churning of the stomach. This causes the carbs to be churned into chyme.The starch is combined with water to form matlose. The maltose is added with more water and is converted into glucose by maltase, which is an enzyme.
2. Proteins: Proteins are broken down by pesinogens (pepsin) in the stomach. Gastrin is used to release gastric acid. Gastric acid stimulates the release of pepsin, which is the enzyme that breaks down proteins. The protein is broken down into polypeptides, which are broken down into peptides by trypsin. Peptides + water are converted into amino acids by pepsidases.
3. Fats: Fats are broken down into fat droplets (or fat gobules) by bile salts from the gallbladder. When water is added with the fat droplets, lipase converts it into glycerol and fatty acids.
As Shaggy wolfs down this sandwich, its different components are
digested in the body. The starch from the bread is broken down in
the mouth by salivary amylase. The protein from the meat is digested
and broken down into amino acids in the stomach. Fat is broken down
into glycerol and fatty acids by lipase.

Metabolic Pathways

Metabolic pathways include all chemical reactions that take place in a cell. There are two types of pathways: anabolic and catabolic metabolism.

Anabolic Metabolism- involves the buildup of larger molecules from smaller ones. Dehydration synthesis, the process that cells take when they join with molecules to form larger molecules of glycogen, occurs during this metabolic pathway.Muscle buildup is an example of this. Cells build up protein molecules by joining amino acids in a process called dehydration process. Carbohydrate buildup also occurs in the anabolic metabolism pathway. A carbohydrate molecule is built by bonding smaller monosaccharides together in a complex chain. .Glucose is built up into glyogen, amino acids are built up to peptides (100 or more peptides forms a peptide bond), and glycerol and fatty acids are built up into fat.

Catabolic Metabolism- involves the breakdown of large molecules into smaller ones and releases energy. Hydrolysis (another term for digestion) brings about the decomposition of carbohydrates, lipids (fats), and proteins.

When food carbohydrates are swallowed, they are broken down into monosaccharides during hydrolysis (digestion)From there on, the carbs have to make a decision about which pathway to travel through. If the body needs nutrients, the carbs would go through the anabolic pathway, where it would be stored as either glycogen or fat. If the nutrients are not needed in the body, the catabolic pathway converts the carbs into energy, carbon dioxide, and water.

Protein Synthesis

  • Protein synthesis is the process of making new proteins for the cell.
  • The most important place in the cell for protein synthesis is in the cell nucleus.
  • DNA is direct certain info to instruct cells. A codon (a triple DNA nucleotide code, such as AUG) is used for bringing in a type of amino acid to the protein site.
  • mRNA copies a code and tRNA brings the code to replicate the DNA strand to form new polypeptides.

The Endocrine System

The endocrine system coordinates and directs the the activity of cells in the body. external image endocrine.jpg
The endocrine system uses chemical messengers, which are called hormones, that are released into the blood and transported throughout the body. Although the multiple hormones have different effects, the major processes controlled by the hormones are growth, reproduction, development, mobilizing body defenses (against stressors), maintaining electrolyte, water, and nutrient balance the blood, and regulating metabolism.

The Types of Hormones

Although hormones seem similar, there are actually two different types, or categories, of hormones in the endocrine system. These types of hormones have different chemical classifications and make up. The first type of hormone are the amino acid-based molecule hormones. These include protein, peptides, and amines. The other type of hormones are steroids, which are made from cholesterol. These steroids include the sex hormones and those who are produced by the adrenal cortex.

Target Organs

Although hormones are directed in the bloodstream, a given hormone affects certain tissue cells or organs in the body. The are referred to as target cells or target organs. When a cell responds to a hormone, specific protein receptors must be located on the
cell's plasma membrane or its interior. This allows the hormone to attach to the cell.When
the binding is complete, the hormone can begin working on its target cell.
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Negative Feedback Mechanisms

Negative feedback is the process that regulates the amount of hormones that affect a certain organ or bodily function. When too much or a hormone is released into the bloodstream, hormone is inhibited and is no longer released. This process regulates the amount of hormones in the blood. For example, the pituitary gland releases TSH, or thyroid stimulating hormone. This affects the development and functioning of the thyroid. This triggers T4, or Thyroxine to be released by the thyroid. T4 regulates the body's metabolism. When the body reaches a normal level of thyroxine, negative feedback occurs and the hormone is "shut off" so that there is not too much of the hormone in the body.

Control of Hormone Release

In the endocrine system, there are three ways for hormones to be released into the bloodstream. The three categories are hormonal, humeral, and neural stimuli. Each activate hormone release in their own unique ways.
  1. Hormonal Stimuli- This type of stimulus activates endocrine organs so they can release hormones by prodding other hormones. The hormones are released into the bloodstream.
  2. Humeral Stimuli- Hormones are released into the bloodstream when blood levels of certain ions and nutrients change. PTH is an example hormone because it regulates blood calcium levels.
  3. Neural Stimuli- Nerve fibers stimulate certain hormones so that they are released. Their target cells are said to respond to the neural stimuli. An example is the sympathetic nervous system sending a signal to release epinephrine and nonepinephrine during times of stress.
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The Major Endocrine Organs and their main Hormones

  • Pituitary Gland- The pituitary gland is split into two organs: the anterior and posterior lobe
- Anterior Lobe- this lobe releases HGH, or Human Growth Hormone that stimulates growth or the bones, muscles, and regulates metabolism. It also releases Thyroid stimulating hormone, which stimulates and regulates the activities of the thyroid gland. It Produces Prolactin, Lutenizing Hormone, and, which helps the development of the gonads.
- Posterior Lobe- this lobe produces oxytocin, which stimulates uterus
contractions during labor. It also releases ADH, which helps water
retention in the kidneys.Hormone release is controlled by releasing or
inhibiting hormones from the hypothalamus.
  • Pineal Body- located in the brain. It releases melatonin, which is involved in biological rhythms in the body. It controls daily rhythms such as sleep habits as well as seasonal rhythms.
  • Thyroid Gland- It releases calcitonin, which reduces blood calcium levels in the blood. It also produces Thyroxine (T4) and triiodothyronine (T3) that stimulates the metabolism of the body.
  • Parathyroid Glands- produces PTH, a hormone that raises blood calcium levels in the blood.
  • The adrenal medulla- produces epinephrine and norepinephrine that raise blood glucose levels, increase the rate of metabolism, and constrict certain blood vessels. This is released in times of stress.
  • Adrenal Cortex- produces Glucocorticoids and mineralocorticoids.The glucocorticoids increase blood glucose levels in the body while the mineralocorticoids promote absorption of NA+ and excretion of K+ in the kidneys.
  • Pancreas- produces insulin when blood glucose levels are too high and releases glucagon when blood glucose is too low. This organ regulates the blood glucose level in the body so that they are at regular levels.
  • Gonads: the gonads are either testes (for males) or ovaries (for females). the testes produce androgens (such as testosterone) that support sperm formation and the development of the secondary male sex characteristics. The ovaries stimulate uterine lining growth and the development of female secondary sex characteristics.

This is a video explaining how the endocrine system functions.

Skeletal System

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The skeletal system provides protection, stability, and the ability to move for the body.The human body is made up 206 bones that support the body's structure and allows the body's limbs to move.

Types of bones
  • Compact Bones- sturdy, dense and smooth, homogenous. An example of this is the femur or the humerous.
  • Spongy Bones- they are composed of small needlelike pieces of bone and a lot of open space.
  • Long Bones- are longer than they are wide. The bones of the arm and the leg are long bones (ex. Femur)
  • Short Bones- generally cube-shaped and contain mostly spongy bone. The bones of the wrist and ankle are example.
  • Flat bones are thin, flattened, and usually curved. They have two thin layers of compact bone sandwiched between a layer of spongy bone. The bones of the skull and the ribs are examples.
  • Irregular Bones-These bones are JV because they do not follow any specific guidelines.

Bone markings

Projections that are sites of muscle and ligament attachment.
  • Tuberosity- large, rounded projection, may be roughened.
  • Crest- narrow ridge of bone, usually prominent.
  • Trochanter- Very large, blunt, irregulary shaped process. the only example is the femur.
  • Line- narrow ridge of bone; less prominent than a crest.
  • Tubercle- small, rounded projection or process.
  • Epicondyle- raised area on or above a condyle.
  • Spine- sharp, slender, often pointed projection.
  • Process- any bony prominence
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Projections that help to form joints
  • Head- bony expansion carried on a narrow neck
  • Facet- smooth, nearly flat articular surface.external image a179972.jpg
  • Condyle- rounded articular projection.
  • ramus- armlike bar of bone.

Depressions and openings allowing blood vessels and nerves to pass.
  • Meatus- canal-like process.
  • Sinus- cavity within a bone, filled with air and lined with mucous membrane.
  • Fossa- shallow, basin-like depression in a bone, often serving as an articular surface.
  • Groove- furrow
  • Fissure- narrow, slit-like opening.
  • Foramen- round or oval opening through a bone.

The skeletal system is divided into two categories of bones: the axial skeleton and the appendicular skeleton.

The Axial Skeleton: The axial skeletonexternal image image001.jpg is comprised of three parts- the skull, the vertebral column, and the bony thorax.

The Appendicular Skeleton: The appendicular skeleton is comprised of the bones of the limbs. These bones include:
  • clavicle
  • scapula
  • humerus
  • ulna
  • radius
  • carpals/metacarpals
  • Phalanges
  • Femur
  • Patella
  • Tibia/fibula
  • Tarsals, metacarpals

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  • The Skull- The skull is formed by two sets of bones. The cranium encloses and protects the fragile brain tissue. The facial bones hold the eyes in an anterior position and allow the facial muscles to show feelings through smiles or frowns.
    • Cranium- consists of the
      • frontal bone-forms the forehead.
      • parietal-paired bones that form the superior and lateral walls of the cranium.
      • temporal- lies inferior to the parietal bones. On the external surface of the temporal bone, there are important parts of the skull. These include the styloid process, the external acoustic meatus, mastoid process, and jugular foramen.
      • occipital- it is the most posterior bone of the cranium. It forms the floor and back wall of the skull.
      • ethmoid- is very irregularly shaped and it forms the roof of the nasal cavity and part of the medial walls of the orbit. external image 4843874113-skull-diagram-superior-view-of-floor-of-cranium-with-labels-axial-skeleton-visual-atlas-page-25.jpg
      • sphenoid bone- butterfly shaped bone that spans the width of the skull and forms part of the floor of the cranial cavity.
    • Facial Bones
      • maxilla -moustache bone
      • mandible jaw bone
      • hyloid bone- only bone that does not articulate with others
      • Vomer- nasal cavity
      • Inferior.middle nasal concha
      • Zygomatic bone- cheekbones.
      • lacriml bones- has a groove for the passageway of tears.
    • Sutures
      • The Coronal Suture- the line where the parietal bones meet the frontal bone.
      • The Sagittal Suture- the parietal bones meet at the midline of the skull at this suture.
      • Squamous suture- it connects the temporal bone with the pairetal bones.
      • Lambdoid Suture- the occipital bone joinsthe parietal bones anteriorly here.

Other Bones.

The Spine Pelvis Scapula

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The hand/arm Bones
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  • Comminuted- bone breaks into many fragments. Particularly common in the aged, whose bones are more brittle.
  • Compression- bone is crushed. Common in porous bones.
  • Depressed- broken bone portion is pressed inward. Typical of skull fracture.
  • Impacted- broken bone ends are forced into each other. Commonly occurs when one attempts to break a fall with outstretched arms.
  • Spiral- ragged break occurs when excessive twisting forces are applied to a bone. Common sports fracture.
  • Greenstick- bone breaks incompletely, much in the way a green twig breaks.

The Muscular System

The muscular system is important for many body functions. Muscle functions include producing movement, maintaining posture, stabilizing joints, and generating heat.

In the human body, there are three different types of muscles:
  • Skeletal Muscles: they consist of skeletal muscle fibers that are packaged into the skeletal muscles. They attach to bones or skin (in the case of a few facial muscles). They are single, very long, cylindrical, multimucleate cells with very obvious striations. They have voluntary contractions and they have no rhythmic contractions. Their speed of contraction varies with the muscle. Examples of skeletal muscles include the biceps brachii, deltoids, pectoralis major, the quadriceps, and the hamstrings.
  • Cardiac Muscles: are located on the walls of the heart. They have branching chains of cells that are uninucleated. They have striations and have involuntary contractions. They have slow contraction speeds and rhythmic contractions.
  • Smooth Muscles: located mostly in walls of hollow visceral organs (other than the heart). They have single, fusiform, uninucleate cells and have no striations. They have involuntary contracts and very slow contraction speeds. They also have rhythmic contractions. Examples of smooth muscles include the muscles lining the digestive organs.

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Major Trunk Muscles

Name of Muscle
Primary Actions
Pectoralis Major
sternum, clavicle,
and first to sixth ribs
Proximal humerus
Adducts and flexes humerus
Rectus Abdominus
Sternum and fifth
to seventh ribs
Flexes vertebral column
External Oblique
Lower eight ribs
Iliac Crest
Flexes and Rotates
vertebral column

Arm/Shoulder Muscles

Name of Muscle
Primary Actions
Biceps brachii
Scapula of
shoulder girdle
Proximal radius
Flexes elbow and
supinates forearm
Distal Humerus
Proximal ulna
Flexes elbow
The shoulder girdle
scapula to clavicle
Proximal humerus
Abducts Arms
Triceps brachii
Shoulder girdle and
and posterior ulna
Olecranon process
Extends Elbow
Flexor carpi radialis
Distal Humerus
Second and third
Flexes wrist and
Flexor carp ulnaris
Distal humerus
and posterior ulna
Carpels of wrist and
fifth metacarpal
Flexes wrist and
Flexor digitorum
Distal humerus,
ulna, and radius
Middle phalanges of
second to fifth fingers
Flexes wrist and
Extensor Carpi Radialis
Base of second and
third metacarpals
Extends wrist and
abducts hand
Extensor digitorum
Distal humerus
Distal phalanges of
second to fifth fingers
Extends fingers
and wrist

Head/Neck/Shoulder Muscles

Name of Muscle
Primary Actions
Cranial aponeurosis
Skin of eyebrows
Raises eyebrows
Orbicularis oculi
Frontal bone and
Tissue around eyes
Blinks and closes eyes
Orbicularis oris
Mandible and maxilla
Skin and muscle around
Closes and protrudes
Temporal bone
Closes jaw
Zygomatic bone
Skin and muscle at
corner of lip
Raises corner of lips
Temporal bone
Closes jaw
Maxilla and mandible
near molars
Oribicularis oris
Compresses cheek as
in whistling and sucking
Sternum and clavicle
temporal bone (mastoid
Flexes neck; rotates
Connective tissue covering
of superior chest muscles
Tissue around mouth
Pulls corners of mouth
Occipital bone and all cervical
and thoracic vertebrae
Scapular spine and
Extends neck and
adducts scapula
Lattisimus dorsi
Lower spine and iliac crest
Ribs, thoracic and
cervical vertebrae
Extends and adducts
Erector spinae
Iliac cress, ribs 3-12, and
Humerus, thoracic and
cervical vertebrae
Extends back
Scapular spine and clavicle
Humerus (deltoid
Abducts humerus

Hip/Thigh/Leg Muscles

Name of Muscle
Primary Actions
Quadriceps group (vastus
medialis, intermedius, and
lateralis, rectus femoris
Femur for the vasti,
pelvis for the rectus
Tibial tuberosity via
petallar ligament.
Extends the knee, the
rectus femoris also flexes
the hip on the thigh.
Hamstrings (semitendonosus,
semimembranosus, biceps
Iscial tuberosity
Proximal tibia. head of
fibula for biceps
Flexes knee and extends
Gluteus maximus
Sacrum and illium
Proximal femur
(gluteal tuberosity)
Extends hip (when
forceful extension is required.
Gluteus medius
Proximal femur
Abducts thigh; steadies pelvis
during walking.
Distal femur
Calcaneus (heel via
calcaneal tendon)
Plantar flexes foot and flexes
Proximal tibia and fibula
Plantar flexes foot.
Proximal tibia
Flexes thigh on hip
Adductor Muscles
Proximal femur
Adduct thigh