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This is a guide that breaks down some basics of human biology.

Respiratory System

  • Inspiration inhalation of air- rib cage moves up and out, diaphragm contracts and moves down- pressure in lungs decreases and air comes in.
  • Expiration exhalation of air into the lungs- rib cage moves down and in, diaphragm relaxes and moves up- pressure in lungs increases and air is pushed out
  • Ventilation breathing encompasses both inspiration and expiration

Respiratory Tract

Hair lining the nose, cilia, and mucus clean the air warm and moisten it. As air leaves the body hair picks up moisture and that causes your nose to drip. In the cold it condenses which is why you can see your breath.

  • The nose are nasal cavities: narrow canals separated from one another by a septum composed of bone and cartilage
  • Ciliated cells act as odor receptors. Nerves lead to the brain where impulses are interpreted as smell
  • The Pharynx or the throat funnel passageway that connects nasal and oral cavities to the larynx.

The nasopharynx nasal cavities open above the soft palate. The Oropharynxthe oral cavity opens. The Laryngopharynx opens into the larynx.

  • Tonsils form a protective ring at the junction of the oral cavity and pharynx, which contain lymphocytes that protect against invasion of foreign antigens that are inhaled.
  • Pharynx located air and food ways cross with the esophagus.
  • Larynx cartilaginous structure that serves as a passage for air between the pharynx and the trachea
  • The Trachea or wind pipe connects the larynx to the parimar bronchi. Its walls are made of smooth, connective tissue with c shaped cartilage rings.

The bronchial tree

  • Bronchus or bronchi(plural): The trachea breaks into left and right tubes witch lead to the lungs the bronchi branch into a lots of secondary bronchi that lead to bronchioles. These lead to air sacs called alveoli(alveolus–singular)
  • Lungs are paired cone-shaped organs that occupy the thoracic cavity. The thoracic cavity is separated from the abdominal cavity by a muscle called the diaphragm. Each lung is enclosed by pleura- a double layer of serous membranes that produces serous fluid.
  • Alveoli is where oxygen diffuses across the laveolar wall and enters the bloodstream
  • Surfactant is a film of lipoprotein that lowers the surface tension and prevents them from closing- lungs collapse if you don’t have this film


Urinary System

Functions of Urine

1. Excretion of metabolic wastes-The kidneys excrete metabolic wastes- urea is a byproduct of amino acid metabolism 2. Maintenance of Water-salt and balance-kidneys maintain water salt balance in the blood. 3. Maintenance of Acid-Base Balance- The kidneys regulate acid/base balance in the blood. Ph should remain around 7.4- Secretion of Hormones- kidneys assist the endocrine system in hormone secretion

  • Kidney are paired organs located near the small of the back. Been shaped reddish brown in color.

Ureters conduct urine from the kidneys to the bladder- small tubes.

  • The Urinary bladder stores urine until it’s passed. Three openings, two for the ureters and one for the urethra.
  • Urethra is a small tube that extends from the urinary bladder to an external opening and used to urinate. It is longer in men because is goes through your penis and also carries semen. Womens' urethra tube is not connected to their reproductive organs.
  • Micturition is when sensory nerves send message to the brain to pee, the muscle relax and urine flows. Adults and older children have control of this function.

Kidney structure

  • Renal cortex is the outer layer that dips down in between a radially striated inner layer called the renal medulla.
  • The renal medulla consists of cone shaped tissue masses called renal pyramids.
  • Renal Pelvis is the cavity continuous with the ureter.
  • Nephrons produce urine, urine flows into collecting ducts. Neprhons are in the medulla renal pyramids.


Skeletal System


  • Osteoblasts are bone forming cells.
  • Oseocytes mature bone cells from osteoblasts.
  • Osteoclasts are bone absorbing cells.

Bones are strong because they’re made of mineral salts, calcium phosphate, and protein fibers.

  • Compact bone is highly organized and composed of tube units called osteons. In a cross section bone cells called osteocytes lie in lacunae- which are tiny chambers arranged in concentric circles around a central canal. Osteocytes nearest the center of an osteon exchange nutrients and wastes and blood vessels in the central canal.
  • Spongy Bone has an unorganized appearance. It contains numerous this plates separated by unequal spaces. It is built for strength like braces in a building. The spaces of spongy bone are filled with red bone marrow- a tissue that produces blood cells.
  • Cartilage more flexible gel-like and contains many collagenous and elastic fibers. No nerves, used for joints and is slow to heal. Cells called Chondorcytes lie within lacunae that irregularly grouped.
  • Hyaline cartilage are firm somewhat flexible at the ends of long bones, fond in the nose and ends of ribs andin the larynx and trachea.
  • Fibrocartilage is stronger then Hyaline and withstand tension and pressure. They are found where support is of prime importance, as discs between the vertebrae and knee.
  • Elastic cartilage is more flexible and found in ear flaps and epiglottis.
  • Fibrous connective tissue contains rows of cells called fibroblasts separated by collgenous fibers. This tissue makes up the ligaments that connect bone to bone and the tendons that connect muscles to a bone at joints.


Muscular System

Types of muscles

  • Smooth muscle has fibers which are spindle shaped cells, each with a single nucleus. Smooth muscle is located in the walls of hollow internal organs and it causes these walls to contract. Smooth muscle is involuntary.
  • Cardiac muscle found in the heart wall. Fibers are uninucleated, striated, tubular, and branched which allows the biers to interlock at intercalated disks. Contraction is involuntary
  • Skeletal muscle fibers are tubular, multi nucleated, and striated. They are the muscles attached to the skeleton. You can control these muscles

Function of skeletal muscles

  • Skeletal muscles support the body.
  • Skeletal muscles help maintain a constant body temperature. ATP break down in the muscles heat the body.
  • Skeletal muscles contraction assists movement in cardiovascular and lymphatic vessels, it keeps the blood moving
  • Skeletal muscles protect internal organs and stabilize joints. They have tendons that help hold bones together at joints.

Muscles work in pairs opposite of each other. The origin of a muscle isn on a stationery bone, and the insertion of a muscle is on a bone that moves. A muscle fiber has many myofibrils. The sarcomere of a myofibril contain myosin and actin filaments, whole arrangement gives rise to the striation characteristics of skeletal muscle tissue. Muscle contraction occurs when sarcomeres shorten and actin filaments slide past myosin filaments.

  • Fermentation supplies ATP without consuming oxygen. When you are all out of breath, muscle can use fat and glycogen to make ATP.
  • Cellular Respiration completes in the mitochondria and provides most of the muscles with ATP.


Nervous System

Central Nervous system(CNS) consists of the brain and spinal cord.

Peripheral nervous system (PNS)- are the nerves.

Neuron Structure

  • Neurons are cells that transmit nerve impulses between parts of the nervous system.


  • Neuroglia support and nourish neurons
  • Sensory neuron takes messages from receptor to the CNS.
  • Sensor Receptors detect environment changes

Neurons have 3 parts

  • Cell body contains nucleus and organelles
  • Dendrites are the many short extensions that receive signals from sensory receptors or other neurons.
  • Axon the portion of a neuron that conducts nerve impulses. Also called nerve fiber.
  • Myelin sheath covers axon, myelin is a lipid serves as a passage way from growth if the nerve is cut.

Spinal Chord

The Spinal chord is the communication line between the brain and the peripheral nerves that leave the chord.


The Brain

  • Cerebrum largest part of the brain- last center to receive sensory input- carries out higher thought processes required for learning and memory and for language and speech. Split into two cerebral hemispheres
  • 'Cerebral cortex is the thin but highly convoluted outer layer of gray matter that comers the cerebral hemispheres. Accounts for sensation, voluntary movement and the thought processes we associate with consciousness
  • Cerebellum receives input from eyes, ears, joints and muscles about present position of body parts and receives motor output from the cerebral cortex about these parts should be located. Maintains posture and balance.
  • Brainstem contains midbrain, the pons and the medulla oblongata.
  • Midbrain acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum- ti has reflex centers for visual auditory and tactile responses
  • Pons means bridge- contains bundles of axons between the cerebellum and rest of the CNS. Regulates breathing rate and head movement reflex.
  • Medulla oblongata- regulates heartbeat, breathing and blood pressure. Also reflex’s for vomiting , coughing , sneezing, hiccuping, and swallowing.


Autonomic System

Autonomic system regulates the activity of cardiac and smooth muscles and glands- the involuntary nerves.

  • Sympathetic shuts shit down for survival like when your running from the pigs. Starts the Emergency procedures, like adrenaline
  • Parasympathetic- relaxes shit when it’s kick back time



Exteroceptors- senses outside the body

Interoceptors- senses within like blood pressure, blood ph

Chemoreceptors- respond to chemical substances.....used for taste and smell Pain receptor- a chemoreceptor - chemicals released from damaged tissue

Photoreceptor- respond to light energy- eyes

Mechanoreceptors- respond to pressure- balance is from a response fluid pressure

Thermoreceptor- respond to temperature-

Sensation- impulses arrive at the cerebral cortex

Perception- interprets the meaning of sensations


Taste buds- embedded in the tongue- they take a weighted average of the different tastes and send it to the brain

Olfactory cells- used for the sense of smell-


Vision: The Eyes=

  • sclera- outer layer of the eye
  • cornea- window of the eye
  • choroid- middle layer- towards the front it becomes the iris-regulates the size of the pupil- hole in the center of the iris where light enters the eyeball
  • Aqueous Humor- clear fluid in the anterior compartment
  • ciliary body- has the ciliary muscle with controls the shape of the lens for near and far vision
  • Rod cells- photoreceptors- more cells, better resolution, for seeing black and white- good for night vision
  • Cone cells- photoreceptors- detects color and bright light- allows detection of fine detail-
  • Nearsighted- people can see up close but no far away
  • Farsighted- people can see far away, but they can’t read a book up close.



Ear has 3 divisions

  • Outer ear consists of the pinna(your frybread) and auditory canal- modified with hair and sweat glands to make ear wax to protect your shit-
  • Middle ear openings called the oval window and round window- has three small bones- ossicles........................malleus(hammer), incus(anvil), stapes(stirrup)

Auditory tube(eustachian tube)o- that’s that shit that pops when you on a plane- permits equalization of pressure

  • Inner ear Filled with fluid- Semicircular canals and the vestibule- for equilibrium- the cochlea(snail)- for hearing

Basically noise makes the middle ear bones shake- sends vibration to the inner ear- the fluid shakes tectorial membrane(little hairs) it up to the brain via the cochlear nerve where it’s interpreted as sound-