Chapter One: Human Organism
Thursday, 6 July 2023
11:00 pm
Anatomy, Physiology and its branches
Anatomy:
-Derived from the Greek Word "Anatome" meaning to "cut up" or to "dissect".
-Study of structures that constitute the human body and how they relate with each other.
-Studies structure and relationship between body part.
Developmental Anatomy:
-Branch of Anatomy that starts with the study of the structural changes right from the fertilization to the maturity stage. (Between
conception and adulthood)
Embryology:
-Subspecialty, Study of developmental of an embryo from the stage of ovum fertilization through the fetal stage. (From conception
to the end of the eighth week of development)
[Needs Microscope]
Cytology:
-Examines structural features of cells.
Histology:
-Examines tissue, composed of cells and materials surrounding them, from various organs.
Gross Anatomy:
-Studies body structure without microscope
• Systemic anatomy: studies functional relationships of organs within a system (the entire body working as a whole).
A "System" is a group of structures that have one or more common functions.
• Regional anatomy: studies body part regionally.
Surface Anatomy :
-involves looking at the exterior of the body to visualize structures deeper inside the body. Using these structures as anatomical
landmarks to identify regions of the body.
• Anatomical Imaging: Usage of radiographs (x-ray), ultrasound, magnetic resonance imaging (MRI), and other technologies to
create pictures of internal structures.
Types Anatomical Imaging
This extremely shortwave electromagnetic radiation (X-ray) moves through the body,
exposing a photographic plate to form a radiograph . Radiographs create flat, twodimensional (2D) image.
• Uses electromagnetic radiation to pass through your body and exposing
structures within a flat plate.
Ultrasound uses high-frequency sound waves, which strike internal organs and
bounce back to the receiver on the skin. Among other medical applications,
ultrasound is commonly used to evaluate the condition of the fetus during
pregnancy.
• Uses high-frequency sound waves that strike internal organs and bounces back
to the skin with the receiver.
Computed tomographic (CT) scans are computer-analyzed x-ray images (a). Some
computers are able to take several scans short distances apart and stack the slices to
produce a 3D image of a body part (b).
• CT scans can be (a) computer analyzed x-rays with better details or (b) a
compilation of several scans that produce a 3d image of a body part.
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Digital subtraction angiography (DSA) is one step beyond CT scanning. A radiopaque
dye is injected into the blood, which allows for enhanced differences when
compared to a noninjected scan.
• A better CT Scan but using Radiopaque dye injected into blood in circulation
allowing for enhanced differences.
Magnetic resonance imaging (MRI) directs radio waves at a person lying inside a
large electromagnetic field. An MRI is more effective at detecting some forms of
cancer than a CT scan.
• Aligns hydrogen protons in the body using an electromagnetic field, then a
radio wave is added to resonate with the hydrogen protons. When the radio
wave is turned off the hydrogen emit a signal, used to create an image.
Positron emission tomographic (PET) scans can identify the metabolic states of
various tissues. This technique is particularly useful in analyzing the brain. Radiation
pinpoints cells that are metabolically active.
• Uses a Radiotracer, radioactive substance injected into the body, emits
positrons which are positively charged particles. When positrons collide with
electrons they produce gamma rays and the Pet Scanner detects these gamma
rays and creates an image of organ and tissue.
Physiology:
-Scientific investigation of the process and functions of living things.
-Derived from the Greek word "Phusis" (?) for the study of nature. Studies how the body and its part work or function.
Two major goals when studying Physiology:
• Examining the body's response to stimuli
• Examining the body's maintenance of stable internal conditions within a narrow range of values in a constantly changing
environment
Cell physiology: examines the process occurring in cells
Systemic physiology: considers functions of organ systems
Cardiovascular physiology: focuses on heart and blood vessels
Neurophysiology: focuses on the function of nerve systems
Pathology:
-Medical Science dealing with all aspects of disease, emphasis on cause and development of abnormal conditions, also structural and
functional changes from disease.
Exercise physiology: deals with functional and structural changes brought by exercise.
Levels of Organization
Chemical Level:
-Atoms interact and combine in order to create structural and functional characteristics of all organisms. Atoms such as hydrogen and
carbon interact to form molecules. A molecule's structure defines its function.
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Cell Level:
-"Cells" are the basic structural and functional units of all living organisms.
-Combination of molecules form cells. Structures inside cells are called "Organelles" which carry out particular functions such as digestion
and movement.
Tissue Level:
-Tissues are formed by groups of similar cells and the materials surrounding them. Characteristics on the types of cells and materials
determine the function of the tissue.
Four basic types of cells:
• Epithelial: They form the covering of all body surfaces, line body cavities and hollow organs. These are also the major tissues in
glands.
• Connective: Contributes to numerous body functions, including supporting organs and cells, transporting nutrients and wastes,
defending against pathogens, storing fat, and repairing damaged tissues.
• Muscle: Composed of cells that have the ability to shorten or contract in order to create movement. Tissue is highly cellular
and well supplied with blood vessels.
• Nervous: Responsible for coordinating and controlling many body activities. Found in the brain, spinal cord and nerves.
Organ Level:
-An organ is composed of two or more tissue types that perform one or more common functions.
Organ System Level:
-Multiple organs that combine in order to create an organ system that together perform a common function or set of functions, therefor
viewed as a unit.
-11 major organ systems: Integumentary, Skeletal, Muscular, Nervous, Endocrine, Cardiovascular, Lymphatic, Respiratory, Digestive,
Urinary, Reproductive.
Organism Level:
-An "Organism" is any living thing considered as a whole-whether composed of one cell, such as bacterium, or of trillion cells, such as a
human. Human organism is a combination of all the organ systems.
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Characteristics of Life
-Guidelines used to determine whether something is considered as "Alive"
• Organization
-Specific interrelationships among the parts of organism and how those parts interact to function.
• Metabolism
-The ability to use energy and to perform vital functions.
-All chemical reactions taking place in the cells and internal environment of an organism.
-i.e. digestive systems breaking down food molecules to get energy and raw materials. Energy is also used to rearrange the
shape of molecules, molecular shape determines function.
• Responsiveness
-An organism's ability to sense changes in its external or internal environment and adjust to those changes.
-Cell to cell communication, the nervous and endocrine systems regulate responses to changes in the environment.
-Responses can include actions such as moving towards food or water, moving away from danger and poor conditions.
• Growth
-Refers to an increase in size or number of cells, which produces an overall enlargement of all or part of an organism. An
increase in materials surrounding cells can contribute to growth.
• Development
-Changes an organism undergoes through time, beginning through fertilization and ending with death. The greatest
development occurs before birth but many changes continue after birth, some go on throughout life. Development includes
growth but also includes differentiation and morphogenesis.
-Differentiation: involves changes in a cell's structure and function from an immature, generalized state to a mature,
specialized state.
-Morphogenesis: is the change in shape of tissues, organs and the entire organism.
• Reproduction
-Formation of new cells or new organisms. Reproduction of cells allows for growth and development. Allows all living
organisms to pass their genes into offspring.
Homeostasis:
-Is the existence and maintenance of a relatively constant environment within the body. As body undergo everyday processes, we are
continuously exposed to new conditions. Changes in external conditions can result in changes in our internal body conditions.
-Changes in internal body conditions are called "Variables" because their values are not constant. To achieve and maintain homeostasis,
the body must actively regulate responses to changes in variables. For cells to function normally they must be in normal range.
-Homeostatic mechanisms normally maintain the body in near an ideal normal value or set point.
-Under normal conditions, homeostasis is maintained by adaptive mechanisms ranging from control center in the brain to hormones
secreted by organs.
-Some functions controlled by Homeostasis mechanisms are blood pressure, body temperature, breathing and heart rate.
Feedback loops:
-Regulates homeostasis. A feedback loop allows for a process to be regulated by the outcome.
-A changed variable is a "stimulus" because it initiates homeostatic mechanism.
• Negative feedback:
-"To decrease", negative feedback is when any deviation from a set point is made smaller or is resisted. Response by the
effector is stopped once the variable returns to its set point. Regulates most systems in the body.
-Examples would be maintaining body temperature, thermoreceptors monitor body heat and sends a message to the
hypothalamus wherein it controls values. If response is necessary the body will secrete sweat to bring it back in normal
levels.
• Positive feedback
-"To increase", occurs when a response to the original stimulus results in the deviation from the set point becoming even
greater.
-Examples would be present during blood loss, a chemical called "Thrombin" is responsible for blood clot formation and
is stimulated to produce more thrombin. By continuing to produce more thrombin, a disruption in homeostasis (blood
loss) is resolved through positive feedback mechanism (blood clotting). The entire process of clot formation is selflimiting, chemicals needed for cloth formation will be depleted.
-Feedback loops have 3 components:
• Receptor: Monitors the value of a variable by detecting stimuli
• Control Center: Establishes the set point around which the variable is maintained
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• Control Center: Establishes the set point around which the variable is maintained
• Effector: The feedback, generates response to adjusts values.
Hormones that increase Blood sugar and decrease blood sugar.
1. Glucagon:
- Source: Produced by alpha cells in the pancreas.
- Function: Released when blood sugar levels are low (e.g., between meals or during fasting).
- Action: Stimulates the liver to release stored glucose (glycogen) into the bloodstream through glycogenolysis. Also promotes
gluconeogenesis, creating glucose from non-carbohydrate sources.
2. Adrenaline (Epinephrine):
- Source: Released by the adrenal glands in response to stress or signals from the nervous system.
- Function: Rapidly increases blood sugar during "fight or flight" responses.
- Action: Enhances glycogenolysis in the liver and muscle cells, releasing glucose for immediate energy. Also reduces glucose uptake by
non-essential cells.
3. Cortisol:
- Source: Produced by the adrenal glands, primarily in response to stress.
- Function: Maintains blood sugar levels during prolonged stress or fasting.
- Action: Promotes gluconeogenesis by converting amino acids and other substrates into glucose. Reduces glucose utilization by cells,
ensuring a steady supply for vital functions.
4. Growth Hormone:
- Source: Produced by the pituitary gland.
- Function: Supports growth and cell regeneration, also impacting metabolism.
- Action: Reduces glucose uptake by muscle and fat cells, sparing glucose for essential tissues. Enhances gluconeogenesis during periods
of fasting or stress.
5. Insulin:
- Source: Produced by beta cells in the pancreas.
- Function: Lowers blood sugar levels after meals.
- Action: Facilitates glucose uptake by cells, particularly muscle and fat cells, promoting storage and utilization. Inhibits glycogenolysis and
gluconeogenesis, preventing excessive blood sugar elevation.
In summary, these hormones collaborate to ensure that the body maintains stable blood sugar levels for energy needs. Glucagon,
adrenaline, cortisol, and growth hormone elevate blood sugar when necessary, while insulin works to lower it and store excess glucose.
This delicate interplay helps prevent both hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar) while adapting to various
physiological states.
Anatomical Position:
-Starting points for positional references to the body.
-Subject is standing erect and facing the observer, the feet are together and the arms are hanging at the sides with the palms facing
forward.
-A person is supine when lying face upward and prone when lying face downward.
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Relative Directional Terms:
-Standardized terms of reference used when describing the location of the body part.
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Body parts Regions
.
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The Abdomen is often subdivided superficially into quadrants by two imaginary lines-one horizontal and one vertical- that intersects at the
navel. In addition to quadrants, the abdomen is often subdivided into regions by four imaginary lines-two horizontal and two vertical.
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Body planes and sections
-Imaginary surfaces or planes lines that divide the body in to sections.
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Sagittal plane:
-Divides the body into right and left half
Mid sagittal plane:
-Divides body into equal left and right halves.
Para sagittal plane:
-Divides the body into unequal left and right
Median plane:
-Is a sagittal plane that passes through the midline, dividing it into equal right and left halves.
-Divides the body into asymmetrical anterior and posterior sections.
Transverse (Horizontal) plane:
-Divides the body into upper and lower body section.
-Runs parallel to the ground, dividing the body into superior and inferior portions
Frontal (Coronal) plane:
-Divides the body into front (anterior) and back (posterior) halves. For example, the coronal suture on the skull is located across the top,
where a person might wear a crown.
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Organs are also sectioned:
Longitudinal section: a cut through the length of the organ
Transverse (Cross) section: a cut at a right angle to the length of an organ
Oblique section: a cut made across the length of an organ at other than a right angle
Body Cavity
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• Dorsal Cavity
-Encloses the organs of the nervous system, the brain, the spinal cord. The two subdivision of the dorsal cavity are the (1)
cranial cavity and the (2) vertebral cavity. Both the brain and spinal cord are covered by membranes called meninges.
• Ventral Cavity
-Houses the vast majority of our internal organs collectively referred to as the viscera. It has two major subdivisions
which are the (1) Thoracic cavity and the (2) Abdominopelvic cavity.
• Thoracic cavity
-More superior to the abdominopelvic cavity and houses primarily the heart and the lungs. Further
subdivided into sections: (1) two lateral pleural cavities, each of which encloses a lung and is surrounded by
ribs and (2) a medial mediastinum, which houses the heart and its major blood vessels, in addition to the
thymus, the trachea and the esophagus.
• Abdominopelvic cavity
-Enclosed by abdominal muscles and consists of (1) the more superior abdominal cavity and (2) the more
inferior pelvic cavity. The organs within the abdominopelvic cavity are housed within the peritoneal cavity.
The abdominal cavity contains majority of the digestive organs, such as the stomach, the intestines and the
liver, in addition to the spleen. The pelvic cavity continues below the pelvis and contains the urinary bladder,
urethra, rectum of the large intestine, and reproductive organs.
Serous membrane of the ventral body
-The walls of the body cavities and the surface of the internal organs are in contact with membranes called "Serous membranes" and
these membranes are double layered.
• Parietal serous membrane: The layer that lines the walls of the cavities
• Visceral serous membrane: The layer covering the internal organs
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Thoracic Cavity Membranes
• Pericardial Cavity
-The pericardial cavity is a space in the mediastinum that houses the heart.
-It is surrounded by two layers of serous membranes: the parietal pericardium and the visceral pericardium.
-The space between these membranes is called the pericardial cavity and is filled with pericardial fluid.
• Pleural Cavities
-Each lung is housed in a pleural cavity, with the parietal pleura lining the cavity and the visceral pleura covering the lungs.
-The pleural cavity is the space between the parietal and visceral pleura.
-The pleural cavity is filled with pleural fluid, which helps reduce friction during lung movement.
• Peritoneal Cavity
-The peritoneal cavity houses various internal organs, including the liver, digestive organs, and reproductive organs.
-The parietal peritoneum is the serous membrane that lines the peritoneal cavity, while the visceral peritoneum covers the
organs within the cavity.
-The parietal peritoneum is the serous membrane that lines the peritoneal cavity, while the visceral peritoneum covers the
organs within the cavity.
• Retroperitoneal organs are located behind the peritoneum, which is the serous membrane that lines the abdominal
cavity.
• Organs such as the kidneys, ureters, adrenal glands, parts of the pancreas, sections of the large intestine, and the
urinary bladder have a retroperitoneal location.
• These organs are tightly adhered to the posterior body wall and are covered by peritoneum only on their peritoneal
cavity side.
• Pericarditis: Inflammation of the pericardium, the serous membrane that surrounds the heart.
• Pleurisy: Inflammation of the pleura, the serous membrane that separates the lungs and the chest wall.
• Peritonitis: Inflammation of the peritoneum, the serous membrane that lines the abdominal cavity and covers
the abdominal organs.
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