Example: The sternum (breastbone) is anterior to the spine.
Posterior (Dorsal):
Refers to the back of the body or a body part.
Example: The heart is posterior to the sternum.
Superior (Cranial or Cephalic):
Indicates that a body part is above another or toward the head.
Example: The head is superior to the abdomen.
Inferior (Caudal):
Means that a body part is below another or toward the lower end of
the body.
Example: The stomach is inferior to the lungs.
Medial:
Describes a position closer to the midline of the body.
Example: The nose is medial to the eyes.
Lateral:
Refers to a position further from the midline, toward the
sides.
Example: The ears are lateral to the nose.
Proximal:
Indicates that a body part is closer to the point of attachment to
the trunk or another reference point.
Example: The shoulder is proximal to the elbow.
Distal:
Describes a position farther from the point of attachment or another
reference point.
Example: The wrist is distal to the elbow.
Superficial (External):
Means a position closer to the surface of the body or a body
part.
Example: The skin is superficial to the muscles.
Deep (Internal):
Refers to a position further away from the surface, closer to the
internal core of the body.
Example: The bones are deep to the muscles.
Intermediate:
Indicates a structure that is between two other structures.
Example: The collarbone is intermediate between the breastbone and
the shoulder.
Glomerulus and Bowman’s Capsule
Glomerulus
It’s a cluster of capillaries surrounded by the Bowman’s capsule
located at the beginning of a nephron in the kidney.
The glomerulus is responsible for filtering blood to form a
protein-free filtrate, which is the first step in the process of
producing urine.
Blood pressure forces water and small molecules (like electrolytes,
glucose, and amino acids) out of the blood and into the Bowman’s capsule
while larger proteins and blood cells remain in the bloodstream.
Bowman’s Capsule
A cup-like sac encircling the glomerulus that receives the filtrate
produced by the glomerulus.
This filtrate, once collected, is passed down the nephron for
further processing into urine.
The Bowman’s capsule is part of the renal corpuscle and has two
layers: the parietal layer (simple squamous epithelium) and the visceral
layer (podocytes that closely surround glomerular capillaries).
Kidney and Ureters
Kidney:
Each kidney is a bean-shaped organ located on either side of the
spine just below the rib cage.
They filter approximately 120-150 quarts of blood daily to remove
waste, excess salts, and water to form urine.
The kidneys are also involved in hormone production (e.g.,
erythropoietin for red blood cell production) and regulate blood
pressure, electrolytes, and acid-base balance.
They contain millions of nephrons, the basic structural and
functional units responsible for urine formation.
Ureters:
Two thin tubes that connect each kidney to the bladder.
They are muscular structures that propel urine using peristalsis (a
wave-like contraction) from the kidneys to the bladder.
The ureters have a valve mechanism that prevents urine backflow once
it enters the bladder.
Anti-diuretic Hormone (ADH) and Ureters
Anti-diuretic Hormone (ADH)
Also known as vasopressin, it’s produced by the hypothalamus and
stored in the posterior pituitary gland.
ADH is released into the bloodstream when blood osmolality (solute
concentration) rises or blood volume decreases.
It acts on the kidney’s collecting ducts, increasing their
permeability to water. This results in more water being reabsorbed from
the urine back into the bloodstream, reducing urine volume and
concentrating the urine.
This hormone plays a crucial role in maintaining fluid balance,
preventing dehydration.
Ureters:
As mentioned, they carry urine from the kidneys to the bladder.
Their smooth muscle walls help propel urine via peristalsis, and the
valves at the bladder end prevent backflow.
Functions in the Urinary System and Reproductive System:
Male Urethra
Urinary System
The primary role is to remove waste and excess substances from the
bloodstream.
Comprises the kidneys, ureters, bladder, and urethra.
Helps regulate blood volume, pressure, electrolyte levels, and
acid-base balance through filtration, reabsorption, secretion, and
excretion processes.
Produces hormones like renin and erythropoietin, contributing to
blood pressure regulation and red blood cell production.
Male Urethra:
A tube that connects the urinary bladder to the external urethral
orifice.
It has a dual function: transporting urine from the bladder during
urination and conveying semen during ejaculation.
The male urethra is longer than the female urethra and consists of
three regions: prostatic, membranous, and spongy (penile) urethra.
Complement System
A series of over 30 small proteins in the blood plasma that work
with (complement) the immune system to destroy pathogens.
Activated in response to the presence of antibodies bound to
pathogens or directly by pathogen surface proteins.
Major roles include:
Opsonization: Coating pathogens with complement
proteins to enhance phagocytosis.
Chemotaxis: Recruiting immune cells to infection
sites.
Cell lysis: Forming membrane attack complexes (MAC)
that create pores in pathogen cell membranes, leading to cell
death.
Immune Clearance: Assisting in clearing immune
complexes from the circulation.
Cell Behavior in Hypertonic and Hypotonic
Solutions
Hypertonic Solution
A solution with a higher solute concentration than the inside of the
cell.
Water moves out of the cell into the hypertonic solution due to
osmosis, causing the cell to shrink (crenate).
Hypotonic Solution
A solution with a lower solute concentration than the inside of the
cell.
Water enters the cell due to osmosis, causing the cell to swell and
potentially burst (lyse) if excess water isn’t managed.
Isotonic Solution
Has the same solute concentration as inside the cell, resulting in
no net movement of water. The cell retains its normal shape.
Type of Epithelium on the Bladder
Transitional Epithelium
Also called urothelium, this type of epithelium lines the bladder,
ureters, and upper part of the urethra.
It consists of several layers of cells that change shape in response
to bladder distension, enabling the bladder to expand and contract.
The surface cells appear round or dome-shaped when the bladder is
empty but become flattened when the bladder is full.
Its elasticity and protective properties help the bladder withstand
the stress of urine storage and emptying while preventing urine from
permeating into surrounding tissues.
Innate vs. Adaptive Immunity
Innate Immunity
Overview: The body’s first line of defense,
providing immediate but non-specific protection.
Components:
Physical Barriers: Skin and mucous membranes
prevent pathogen entry.
Chemical Barriers: Acidic environments (stomach
acid) and enzymes (lysozyme in saliva and tears) destroy pathogens.
Cellular Defenses: Phagocytic cells (macrophages,
neutrophils) ingest pathogens, while natural killer cells destroy
infected or cancerous cells.
Adaptive Immunity
Overview: A highly specific immune response that
develops upon exposure to a specific pathogen or antigen.
Components:
Humoral Immunity: B cells produce antibodies to
neutralize extracellular pathogens.
Cell-Mediated Immunity: T cells target and destroy
infected host cells, activate other immune cells, and regulate immune
responses.
Mucous Membranes
Structure: Mucous membranes consist of an
epithelial layer that secretes mucus, and a connective tissue layer
underneath. Goblet cells within the epithelium are responsible for mucus
production.
Function:
Trap and remove pathogens, dust, and particles.
Moisturize and protect underlying tissues from mechanical damage and
dehydration.
Line respiratory, digestive, and urogenital tracts to act as
barriers against harmful microorganisms.
Antibodies (Immunoglobulins)
Overview: Y-shaped proteins produced by B cells as
part of the adaptive immune system.
Structure:
Two heavy chains and two light chains form a Y-shaped molecule with
constant (Fc) and variable (Fab) regions.
The variable region binds specifically to antigens.
Classes:
IgG: Most abundant; provides long-term immunity and
crosses the placenta.
IgM: First antibody produced; effective in
agglutination and complement activation.
IgA: Found in mucous secretions; protects mucosal
surfaces.
IgE: Involved in allergic responses and defense
against parasites.
IgD: Found on B cell surfaces; functions as a
receptor.
B and T Cells
B Cells
Development and Maturation: Originate and mature in
the bone marrow.
Functions:
Plasma Cells: Produce and secrete antibodies in
response to pathogens.
Memory B Cells: Retain the memory of specific
antigens, enabling rapid response upon re-exposure.
T Cells
Development and Maturation: Originate in the bone
marrow but mature in the thymus.
Functions:
Helper T Cells (CD4+): Activate other immune cells,
including B cells and cytotoxic T cells.
Cytotoxic T Cells (CD8+): Directly destroy infected
or cancerous cells.
Regulatory T Cells: Suppress excessive immune
responses and maintain self-tolerance.
Adrenal Glands
Location: Sit on top of the kidneys, each weighing
about 4-5 grams.
Structure:
Cortex: Outer layer responsible for steroid hormone
production.
Medulla: Inner region that produces catecholamines
(adrenaline, noradrenaline).
Hormones:
Cortisol: Glucocorticoid that regulates metabolism
and the stress response.
Aldosterone: Mineralocorticoid that helps maintain
blood pressure by regulating sodium and potassium levels.
Adrenaline and Noradrenaline: Fight-or-flight
hormones that increase heart rate, blood flow, and energy
availability.
Pancreatic Islets
Structure: Clusters of endocrine cells within the
pancreas.
Major Cell Types and Their Hormones:
Alpha Cells: Produce glucagon, which raises blood
sugar levels.
Beta Cells: Produce insulin, which lowers blood
sugar levels.
Delta Cells: Produce somatostatin, which regulates
other pancreatic hormones.
Androgens
Definition: A group of steroid hormones, the most
well-known being testosterone.
Production:
Mainly produced in the testes and adrenal glands.
Small amounts are also produced in the ovaries.
Functions:
Promote male sexual development, spermatogenesis, and libido.
Influence muscle growth, bone density, and red blood cell
production.
Androgens also have minor roles in female physiology, such as libido
and hormone balance.
Antigens
Definition: Substances that provoke an immune
response by binding to specific antibodies or T cell receptors.
Types:
Exogenous: Enter the body from the external
environment (bacteria, viruses, toxins).
Endogenous: Arise within the body (infected cells,
cancer cells).
Autoantigens: Self-antigens that can trigger
autoimmune disorders if recognized by the immune system.
Microvilli
Structure: Tiny, finger-like projections that
increase surface area on epithelial cells.
Function:
Found predominantly in the small intestine to maximize nutrient
absorption.
Contain enzymes on their surfaces to help digest nutrients before
absorption.
Glomerulus and Bowman’s Capsule
Glomerulus:
Network of capillaries that filters blood to produce a protein-free
filtrate.
Blood pressure forces water and small solutes through the capillary
walls into the Bowman’s capsule.
Bowman’s Capsule:
Cup-like sac that surrounds the glomerulus and collects the
filtrate.
This filtrate moves through the nephron’s tubules for further
processing into urine.
Thymus
Location and Structure: Located in the upper chest,
it shrinks with age (largest during childhood).
Function:
Site of T cell maturation and differentiation.
Produces hormones like thymosin that promote T cell development and
immune function.
Kidney Failure and Dialysis Machine
Kidney Failure: A condition where the kidneys lose
their ability to filter and eliminate waste from the blood.
Dialysis Machine:
A life-saving device used in cases of end-stage renal disease.
Filters waste products, excess water, and toxins from the blood,
replacing the kidney’s filtering function.
Two main types:
Hemodialysis: Blood is filtered through a machine
using a dialyzer (artificial kidney).
Peritoneal Dialysis: The lining of the abdomen
(peritoneum) acts as the filter to remove waste.
Loop of Henle
Part of the nephron that lies between the proximal and distal
convoluted tubules.
Has a descending limb that permits water reabsorption and an
ascending limb that allows salt reabsorption.
Generates a concentration gradient in the kidney, crucial for water
reabsorption and urine concentration.
Autoimmune Disorders: Allergy, Rheumatoid Arthritis,
AIDS
Allergy: An exaggerated immune response to
allergens, such as pollen, food, or animal dander. Symptoms include
sneezing, itching, and rashes.
Rheumatoid Arthritis:
An autoimmune disorder where the immune system attacks the
joints.
Causes pain, swelling, and deformities, primarily in hands and
feet.
AIDS (Acquired Immunodeficiency Syndrome):
Caused by the Human Immunodeficiency Virus (HIV), which attacks the
immune system, particularly CD4+ T cells.
Leads to severe immunodeficiency, making the body vulnerable to
opportunistic infections and certain cancers.
Excessive Growth Hormone
Acromegaly: A condition caused by the
overproduction of growth hormone (GH) by the pituitary gland, often due
to a benign tumor.
Symptoms:
Enlarged hands, feet, and facial features.
Joint pain, thicker skin, and deepened voice.
Can lead to complications like type 2 diabetes and high blood
pressure.
Arterial Blood Pressure
Arteries: Blood vessels that carry oxygenated blood
away from the heart.
Characteristics:
Have the highest blood pressure in the circulatory system due to
proximity to the heart’s pumping action.
Elastic walls help maintain consistent blood flow.
Capillaries: Smallest blood vessels with lower
pressure than arteries, allowing for nutrient and gas exchange.
Contraction and Electrical Signals
Sinoatrial Node (SA Node):
Known as the heart’s natural pacemaker.
Generates electrical signals that trigger atrial contraction.
Atrioventricular Node (AV Node):
Delays the signal slightly before sending it to the ventricles,
ensuring the atria contract before the ventricles.
Systole and Diastole:
Systole: Period of heart contraction, pumping blood
out of the heart.
Diastole: Period of relaxation, allowing the heart
chambers to fill with blood.
Heart Chambers:
The heart’s four chambers (two atria, two ventricles) work together
in a coordinated cycle, with atria contracting slightly before
ventricles.