1. Cells & Tissues Organization Flashcards
Here are the levels of organization in order of complexity from smallest to largest help you to understand the anatomy and physiology of the body:
Chemical > Cellular > Tissue > Organ > System > Organism (the body)
nucleotide bases are
the foundation of the genetic code with the instructions on how to build and maintain the human body from conception through old age. There are about three billion of these base pairs in human DNA.
Types of Tissues
There are four basic types of tissue grouped together by common features of structure and function:
epithelial tissue
connective tissue
muscular tissue
nervous tissue
Epithelial tissue
also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, line internal cavities and passageways (GI tract) and form certain glands
connective tissue:
type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems. tendons, ligaments, bone, fat
muscle tissue:
type of tissue that can contract, generating tension in response to stimulation; produces movement. Cardiac, smooth, skeletal
nervous tissue:
type of tissue that can send and receive impulses through electrochemical signals. Brain, Spinal cord, nerves
pancreas belongs to both
the endocrine and digestive systems.
The systems of the human body include
the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive (male/female) systems.
The integumentary system
consists of the skin and the associated skin components, such as hair, sweat glands, sebaceous glands, and nails.
Function
It protects the body from the external environment, excretes metabolic waste, helps to make vitamin D, and detects pain, touch, dehydration, and changes in temperature.
The skeletal system
consists of the bones and the cartilage associated with joints.
Function
It protects the body, provides support and a framework for muscles to act upon, contains bone marrow for blood cells to develop in, and stores minerals such as calcium.
The muscular system
consists primarily of skeletal muscle, but there are also two other types of muscle: cardiac muscle found in the heart and smooth muscle found within the viscera, including the alimentary canal and the walls of blood vessels.
Function
It enables the body to move by the action of opposing muscular contraction and relaxation. It also maintains posture and plays a role in thermoregulation.
The nervous system i
ncludes the brain, spinal cord, nerves, and special sense organs (e.g., eyes, ears, and taste buds). This system is divided into the central nervous system, containing the brain and spinal cord, and the peripheral nervous system, containing everything else.
Function
The functionality of the nervous system can be split into three main stages:
Detecting changes in the internal and external environment, encoding them into electrical impulses, and transmitting them along the nerves
Processing electrical impulses and making decisions, either consciously or unconsciously
Activating muscles or glands to induce an appropriate response to the initial stimulus
The endocrine system
consists of endocrine organs and endocrine tissue embedded within organs. Endocrine organs include the pituitary, thyroid, pineal, parathyroid, and adrenal glands. Endocrine tissue is also found within the hypothalamus, pancreas, thymus, gonads, heart, stomach, and small intestine.
Function
Hormones alter the metabolism of target cells. The hormone can be very specific, affecting only one cell type, or very general, affecting many cell types.
The cardiovascular system
consists of the blood, heart, and blood vessels.
Function
It pumps blood around the body through the blood vessels to deliver oxygen and nutrients to cells and remove metabolic waste from cells. It regulates the water content of body fluids, the acid-base balance, and the temperature of the body.
The lymphatic system
consists of lymphatic fluid (lymph), lymphatic vessels, lymph nodes, the spleen, lymph nodules, and thymus.
Function
It is responsible for transporting various substances; it takes lipids from the gastrointestinal tract to the blood and transports excess proteins and fluids back to the bloodstream. It is also responsible for the development of lymphocytes, the cells responsible for fighting disease.
The respiratory system
consists of air passageways: the pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
Function
It is responsible for oxygen and carbon dioxide gas exchange with the blood and is also involved in the regulation of acid-base balance and sound production.
The digestive system
consists of the digestive tract (the oral cavity, pharynx, esophagus, stomach, and small and large intestine), as well as organs that assist digestion (the salivary glands, liver, gallbladder, and pancreas).
Function
It is responsible for the breakdown of ingested food, both physically and chemically, so that nutrients can be absorbed. It is involved in the absorption of water and removal of undigested food. It also helps to maintain the fluid, electrolyte, and acid-base balance.
The urinary system
consists of the kidneys, ureters, urinary bladder, and urethra.
Function
It filters blood to extract metabolic waste and maintain the acid-base and mineral balance. It also helps to regulate the production of red blood cells.
The female reproductive system c
ontains the gonads (ovaries), uterine tubes, uterus, vagina, clitoris, labia, and mammary glands.
Function
Female gonads produce oocytes (the cells from which an egg develops) and also release hormones that regulate reproduction and development. The female reproductive system is also responsible for fetal development, childbirth, and the nourishment of the fetus and child.
The male reproductive system c
ontains the gonads (testes), epididymis, ductus deferens, ejaculatory duct, various accessory glands, urethra, penis, and scrotum.
Function
Male gonads produce sperm and release hormones that regulate reproduction and development. Fertilization is the combination of a sperm and an oocyte, resulting in the formation of a new life.
What are the two systems that maintain blood pressure homeostasis?
Urinary and cardiovascular system
It is a group of cells with husimilar function and structure.
tissue
What is the smallest independently functioning biological unit of an organism?
Cell
What is a collection of similar tissues that performs a specific function?
Organ
An organ is an anatomically distinct structure of the body composed of two or more tissue types.
A mitochondrion (plural = mitochondria) is
a membranous, bean-shaped organelle that is the “energy transformer” of the cell.
A lysosome is
an organelle that contains enzymes that break down and digest unneeded cellular components, such as a damaged organelle.
Autophagy
(“self-eating”) is the process of a cell digesting its own structures. Lysosomes are also important for breaking down foreign material.
The Golgi apparatus is responsible for
sorting, modifying, and shipping off the products that come from the rough ER, much like a post office.
A ribosome is
an organelle that serves as the site of protein synthesis.
Cytosol,
the jelly-like substance within the cell, provides the fluid medium necessary for biochemical reactions.
There are three major components of a cell
the nucleus, cytoplasm, and cell membrane.
The cell membrane of the cell is a phospholipid bilayer containing
many different molecular components, including proteins and cholesterol, some with carbohydrate groups attached.
A receptor is a
type of recognition protein that can selectively bind a specific molecule outside the cell, and this binding induces a chemical reaction within the cell.
A ligand is
the specific molecule that binds to and activates a receptor.
A glycoprotein is a
protein that has carbohydrate molecules attached, which extend into the extracellular matrix. The attached carbohydrate tags on glycoproteins aid in cell recognition.
The glycocalyx is a
fuzzy-appearing coating around the cell formed from glycoproteins and other carbohydrates attached to the cell membrane. The glycocalyx can have various roles. For example, it may have molecules that allow the cell to bind to another cell, it may contain receptors for hormones, or it might have enzymes to break down nutrients.
The organelles and cytosol, taken together, compose the cell’s
cytoplasm
The nucleus
is a cell’s organelle that contains the DNA
peroxisome i
s a membrane-bound cellular organelle that contains mostly enzymes. Peroxisomes perform a couple of different functions, including lipid metabolism and chemical detoxification. peroxisomes neutralize poisons such as alcohol.
Peroxisomes are membrane-bound organelles that contain an abundance of enzymes for detoxifying harmful substances and lipid metabolism.
Reactive oxygen species (ROS)
such as peroxides and free radicals are the highly reactive products of many normal cellular processes, including the mitochondrial reactions that produce ATP and oxygen metabolism.
cytoskeleton
helps the cells to maintain their structural integrity. The cytoskeleton is a group of fibrous proteins that provide structural support for cells, but this is only one of the functions of the cytoskeleton.
Cytoskeletal components are also critical for cell motility, cell reproduction, and transportation of substances within the cell.
microtubule,
composed of a protein called tubulin.
- make up two types of cellular appendages important for motion: cilia and flagella.
move rhythmically; they beat constantly, moving waste materials such as dust, mucus, and bacteria upward through the airways, away from the lungs and toward the mouth. Beating …. on cells in the female fallopian tubes move egg cells from the ovary toward the uterus.
Cilia
is an appendage larger than a cilium and specialized for cell locomotion.
A flagellum (plural = flagella)
The only flagellated cell in humans is the sperm cell that must propel itself toward female egg cells.
can serve as the cellular origin point for microtubules extending outward as cilia or flagella or can assist with the separation of chromosomes during cell division.
A centriole
A centriole is a small structure inside the cell that has two main jobs:
1. It can be the starting point for building tiny tubes called microtubules, which grow outward to form cilia (small hair-like projections) or flagella (long tail-like projections). These help the cell move or move things around it.
2. During cell division, centrioles help organize and pull apart the chromosomes, making sure each new cell gets the right set of genetic material.
In short: Centrioles help the cell move and divide by organizing microtubules.
Passive transport
is the movement of substances across the membrane without the expenditure of cellular energy.
Water and oxygen can move across the cell membrane without any energy (passive transport).
active transport
is the movement of substances across the membrane using energy from adenosine triphosphate (ATP).
Simple sugars need energy to move from the blood into a cell to be converted to energy (active transport).
Simple sugars sometimes need energy to move from the blood into a cell to be converted to energy (active transport).
Diffusion
is the movement of particles from an area of higher concentration to an area of lower concentration.
Facilitated diffusion
is the diffusion process used for those substances that cannot cross the lipid bilayer due to their size, charge, and/or polarity (Figure 3.6). A common example of facilitated diffusion is the movement of glucose into the cell, where it is used to make ATP.
Osmosis i
s the diffusion of water through a semipermeable membrane down its concentration gradient.
Osmosis is how water moves in and out of your cells to keep things balanced.
Imagine your cells are little water balloons. Around them is a fluid called extracellular fluid. Osmosis is like a natural water-balancing act: water moves from where there’s more of it (less concentrated with stuff like salt or sugar) to where there’s less of it (more concentrated) through the cell’s outer layer (the cell membrane).
In the human body, this helps:
• Keep cells from drying out or bursting
• Balance fluids between blood and tissues
• Support kidney function, by helping filter and reabsorb water
It’s your body’s way of making sure every cell stays hydrated and works properly.
What is true about the cell membrane?
It is selectively permeable.
sodium-potassium pump:
transports sodium out of a cell while moving potassium into the cell
electrical gradient:
difference in the electrical charge (potential) between two regions
endocytosis:
the process of a cell ingesting material by enveloping it in a portion of its cell membrane
Endocytosis is how a cell takes in large particles or fluids from outside by wrapping them in its membrane.
Here’s how it works in simple terms:
1. The cell notices something outside—like nutrients, fluids, or even bacteria.
2. The cell membrane starts to fold around it, like a little pouch.
3. The pouch closes off and pinches inward, forming a bubble (called a vesicle) inside the cell.
4. Now, whatever was outside is safely inside the cell in that bubble.
There are different types of endocytosis, like:
• Phagocytosis – “cell eating” (for big particles like bacteria)
• Pinocytosis – “cell drinking” (for fluids)
• Receptor-mediated endocytosis – when the cell uses special receptors to take in specific substances (like cholesterol or hormones)
vesicle:
membrane-bound structure that contains materials within or outside of the cell
phagocytosis
the endocytosis of large particles (“cell eating”):
pinocytosis
brings fluid containing dissolved substances into a cell through membrane vesicles (“cell drinking”):
receptor-mediated endocytosis:
the endocytosis of ligands attached to membrane-bound receptors
exocytosis:
the process of a cell exporting material using vesicular transport
Where can DNA be found?
nucleus, chromosome
Prokaryotic cells are
single-cell organisms, such as bacteria.
Osteoblasts are
bone-producing cells found in the bone marrow.
Epithelial cells
line the major cavities of the body.
Oocyte cells .
are made in the ovaries
A lysosome is an organelle that contains
enzymes that break down and digest unneeded cellular components.
Ribosomes (do what)
synthesize proteins
Which organelle is found on rough endoplasmic reticulum and in cytoplasm?
Ribosome
Osmosis is not active transport. It is t
he movement of water molecules from low solute concentration to high solute concentration.
Phagocytosis is known as
“cell eating” and involves endocytosis of large particles.
Exocytosis is a form
of active transport that releases material outside of the cell using vesicles.
Pinocytosis
is a form of endocytosis that brings fluid containing dissolved substances into a cell using vesicles.
Which tissue type includes a single-layer, irregularly shaped columnar cells, and nuclei appearing at different levels?
Pseudostratified columnar
Which tissue protects the integral organ and mostly contains collagen fibers?
Skeletal tissue
Bone protects the internal organ and contains mostly collagen fibers.
Microglia cells are
the primary immune cells of the central nervous system.
Oligodendrocyte cells produce
myelin in the central nervous system.
Schwann cells produce
myelin in the peripheral nervous system.
Which cells in the central nervous system have functions including regulation of ion concentration in the intercellular space, uptake and breakdown of some neurotransmitters, and formation of the blood-brain barrier?
Astrocyte cells
What makes myelin in the peripheral nervous system?
Schwann cells
Which muscle tissues are around the entrance points to the body, including the mouth and anus?
Skeletal muscle tissue
What does the term inferior signify?
A position below or lower than another part of the body proper, near or toward the tail, is described as inferior or “caudal.” The word derives from “coccyx,” which is the lowest part of the human spinal column.
medial:
proximal:
distal:
toward the midline of the body, toward the middle
nearer to the trunk of the body
farthest from the trunk of the body
Which subdivisions are found in the ventral cavity?
Thoracic, abdominal, and pelvic
The thoracic cavity is within the
ventral cavity and contains the lungs and heart.
Which organs are in the left upper quadrant?
Spleen, pancreas, and descending and transverse colon
correct
In which cavity are the brain and the spinal cord located?
Dorsal cavity
Homeostasis is
the existence and maintenance of relatively stable conditions inside the body despite the influence of dynamic and unpredictable internal and external environments. For example, even with fluctuations in the temperature of the external environment, the body maintains a relatively constant internal temperature of approximately 98.6°F (37°C).
Which variables are closely monitored to maintain homeostasis?
Temperature
pH
Salinity
All of the above
In the thermoregulation example, what is a major effect when the heat loss center is stimulated?
Dilation of blood vessels in the skin
Positive feedback
intensifies a change in the body’s physiological condition rather than reversing it.
Childbirth
Clotting when injury and bleeding occurs
homeostatic imbalance
Decreases in the effectiveness or efficiency of either the positive or negative feedback systems can lead to uncontrollable disruptions in homeostasis. This is referred to as homeostatic imbalance and most often results in disease, or in severe cases, death. Disease results from uncontrollable disruptions to homeostasis, which leave regions or systems within the body unable to sustain a normal degree of function. This abnormal functioning results in a recognizable set of signs and symptoms attributable to a specific condition or disease.
Which component is part of a feedback system?
Effector
There are two main types of cells: germ cells and somatic cells.
germ cells and somatic cells.
Somatic cells include:
- epithelial
- blood cells
- osteoblasts
- fibroblasts
- muscle cells
- nerve cells
What is the major difference between smooth and cardiac muscle cells?
Cardiac muscle cells are striated.
Smooth muscle tissue is
-involuntary.
-found in the walls of internal organs, blood vessels, and the intrinsic (internal) muscles of the eye.
Smooth muscle tissue helps to
propel and expel liquid within and from the body, allows peristalsis that aids in digestion, and helps to regulate the diameter of blood vessels.
What holds the contents of the cell, including organelles?
Cytoplasm
What do ribosomes synthesize?
Proteins
the role of the Golgi complex is
To modify, sort, and package proteins and lipids for storage or transport out of the cell.
Each chromosome contains double-stranded molecules that have a double-helix shape. What is the name of this molecule?
DNA
The nucleus sends…
The nucleus sends “commands” to the cell via molecular messengers that translate the information from DNA.
RNA vs DNA
DNA is the blueprint, and RNA is the worker that helps build proteins based on that blueprint.
Main types of RNA:
mRNA (messenger RNA): Carries genetic code from DNA to ribosomes
tRNA (transfer RNA): Brings amino acids to the ribosome during protein synthesis
rRNA (ribosomal RNA): Helps make up the structure of ribosomes
Ribosomes
Ribosomes are the protein factories of the cell. 💪
What they do:
Read the instructions from mRNA (messenger RNA)
Link amino acids together in the correct order
Build proteins, which the cell uses for structure, enzymes, hormones, and more
Where they are:
Floating freely in the cytoplasm → make proteins for use inside the cell
Attached to the rough endoplasmic reticulum (RER) → make proteins for export or use in membranes
So in short:
Ribosomes read the genetic recipe and cook up proteins! 🍳🧬
The chromosome is composed of
DNA and proteins; it is the condensed form of chromatin. It is estimated that humans have almost 22,000 genes distributed on 46 chromosomes.
DNA Macrostructure
Strands of DNA are wrapped around supporting histones. These proteins are increasingly bundled and condensed into chromatin, which is packed tightly into chromosomes when the cell is ready to divide.
DNA - histones - chromatin - chromosomes
A gene is
A gene is a functional segment of DNA that provides the genetic information necessary to build a protein.
One cell cycle has two main phases:
interphase and mitosis with cytokinesis.
Interphase is when the cell grows and prepares to divide—most cells stay in this phase.
Mitosis is when the nucleus divides.
Cytokinesis splits the cytoplasm, forming two separate cells.
Billions of human cells divide daily. During the S phase of interphase…
, DNA is duplicated, creating two identical sister chromatids for each chromosome, joined at a centromere. Since humans have 46 chromosomes, the cell ends up with 92 chromatids.
⚠️ Don’t confuse sister chromatids (exact copies) with homologous chromosomes (one from each parent).
You have pairs of chromosomes in your cells—
one from your mom and one from your dad. These two are called a homologous pair.
Before a cell divides, it makes a copy of each chromosome, like making a twin. These two identical copies are called sister chromatids and they’re stuck together in the middle, forming an “X” shape.
So:
🔴 One red = from mom
🔵 One blue = from dad
Each makes a copy → now they look like two X-shaped sets, side by side!
Mitosis is divided into stages that take place after interphase and in the following order:
prophase, prometaphase, metaphase, anaphase, and telophase. The process is then followed by cytokinesis.
Prophase – Chromosomes condense and become visible; the nuclear envelope starts to break down.
Prometaphase – The nuclear envelope fully breaks down; spindle fibers attach to chromosomes.
Metaphase – Chromosomes line up in the middle of the cell.
Anaphase – Sister chromatids are pulled apart to opposite sides of the cell.
Telophase – New nuclear envelopes form around each set of chromosomes; the cell starts to split.
Cytokinesis – The cell fully divides into two separate daughter cells.
Osteoblasts are
immature bone-producing cells present in bone marrow and other connective tissues.
Fibroblasts are
large, branching cells found in most connective tissues. They make collagen and parts of the extracellular matrix, helping build the structure that supports tissues
What is the function of lysosomes?
Breakdown of large cell components and old cells
Phagocytosis –
The cell “eats” large particles like bacteria by surrounding and engulfing them.
Exocytosis –
The cell “spits out” substances by packaging them in a vesicle that merges with the cell membrane and releases them outside.
A zygote is
the first cell formed when egg and sperm join. It divides quickly to form an embryo. Early cells are totipotent, meaning they can become any cell type. As development continues, three germ layers form:
Ectoderm (outer)
Mesoderm (middle)
Endoderm (inner)
Epithelial tissue comes from all three layers, while nervous tissue forms from ectoderm and muscle tissue from mesoderm.
The human body has four main tissue types:
Epithelial – Covers body surfaces, lines cavities, and forms glands
Connective – Supports, protects, and connects body parts
Muscle – Contracts to enable movement (skeletal, smooth, cardiac)
Nervous – Sends electrical signals for communication across the body
Changes in tissue structure can signal disease and are studied through histology (microscopic tissue study).
A tissue membrane is a
thin layer of cells that covers the body, organs, internal passageways, and joint cavities. There are two main types: connective tissue membranes and epithelial membranes.
Types of Cell Junctions – Short Summary
Cells connect using three main types of junctions: tight, anchoring, and gap junctions.
Tight junctions seal cells closely together, blocking substances from passing between them. They help form selective barriers.
Anchoring junctions (desmosomes, hemidesmosomes, adherens) provide strength and flexibility by connecting cells or linking them to the extracellular matrix.
Desmosomes use cadherins to link cells
Hemidesmosomes use integrins to anchor cells to the base layer
Adherens junctions use actin to support cell shape
Gap junctions create tiny channels between cells to allow the movement of small molecules and ions, helping cells communicate and coordinate.
Epithelial tissues are classified by cell shape and number of layers:
Shapes:
Squamous – flat and thin
Cuboidal – box-shaped
Columnar – tall and rectangular
Layers:
Simple – one layer (all touch the base)
Stratified – multiple layers (only bottom touches the base)
Pseudostratified – looks like multiple layers but is just one
Transitional – cells change shape depending on stretch
Simplified Summary of Simple and Pseudostratified Epithelia
Simple Squamous Epithelium:
Flat, thin cells for fast diffusion
Found in lungs, capillaries, kidney tubules, and serous membranes (mesothelium)
Endothelium lines blood and lymph vessels
Simple Cuboidal Epithelium:
Cube-shaped cells with round nuclei
Functions in secretion and absorption
Found in kidney tubules and gland ducts
Simple Columnar Epithelium:
Tall cells with elongated nuclei near the base
Also for absorption and secretion
Found in digestive tract and female reproductive system
Ciliated columnar cells move mucus/particles (e.g. in fallopian tubes)
Pseudostratified Columnar Epithelium:
Looks like multiple layers, but all cells touch the base
Found in respiratory tract, often ciliated
Contains goblet cells that secrete mucus
Both simple and pseudostratified columnar epithelia may include goblet cells to help trap and move particles.
Stratified and Transitional Epithelium – Short Summary
-Stratified epithelium has multiple layers for protection. It’s named by the shape of the top layer of cells.
-Stratified squamous is the most common:
-Keratinized (with keratin) → found in skin
-Nonkeratinized (no keratin) → found in the mouth
lining
-Stratified cuboidal and columnar epithelium are rare, found in some glands and ducts.
-Transitional epithelium is only in the urinary system (bladder, ureters):
-Apical cells change shape from cuboidal to
squamous as the bladder fills
-Allows for stretch and expansion
-Pseudostratified columnar epithelium looks layered but is a single layer with uneven nuclei; found in the respiratory tract, often with cilia.
Gland Types – Short Summary
1.Endocrine glands release hormones into the bloodstream, targeting specific cells.
Part of the body’s regulatory system
Examples: pituitary, thymus, adrenal glands, gonads
2.Exocrine glands release substances through ducts to body surfaces or cavities.
Examples: sweat, saliva, mucus, breast milk, digestive secretions
Connective Tissue –
Main function:
Connects, supports, and protects tissues and organs.
Unlike epithelial tissue, connective tissue cells are spread out in a matrix of ground substance and protein fibers.
The matrix can be fluid (as in blood) or solid (as in bone), and determines the tissue’s function.
All connective tissues contain:
Cells
Ground substance
Protein fibers
Functions of Connective Tissue
Support & connection: Tendons, ligaments, bones, and tissue coverings
Protection: Bones and fibrous capsules around organs
Defense: Immune cells that fight pathogens
Transport: Blood and lymph carry nutrients and waste
Storage & insulation: Adipose (fat) stores energy and keeps the body warm
Embryonic Connective Tissue
All connective tissues come from the mesoderm layer in embryos
Mesenchyme is the first type and gives rise to all other connective tissues
Wharton’s jelly (mucous connective tissue) is found in the umbilical cord and disappears after birth
Connective tissue is grouped into three main types, based on the matrix and fiber types:
- Connective tissue proper:
- Loose – loosely arranged fibers with space between cells (e.g. fat, areolar tissue)
- Dense – tightly packed fibers for strength and elasticity (e.g. tendons, ligaments)
- Supportive connective tissue:
Cartilage and bone – strong, protect organs; bone has a rigid, calcified matrix - Fluid connective tissue:
Blood and lymph – cells float in a watery matrix with nutrients, proteins, and salts
Cell Types in Connective Tissue – Short Summaryof 6 types
Fibroblasts: Most common; produce the extracellular matrix (fibers + ground substance)
Fibrocytes: Less active form of fibroblasts
Adipocytes: Store fat
White fat – one large droplet, stores energy
Brown fat – many droplets, high metabolism
Mesenchymal cells: Stem cells that can become other connective tissue cells for repair and healing
Macrophages: Immune cells that engulf pathogens and debris
Can be free-moving or fixed in tissue
Release cytokines to signal other immune cells
Mast cells: Contain histamine and heparin
Trigger inflammation during injury or allergic reactions
Part of the immune system, like macrophages
Fibroblasts produce three main fiber types:
Collagen fibers – strong and flexible; provide support and strength (e.g., tendons, ligaments)
Elastic fibers – made of elastin, stretch and return to shape (e.g., skin, spine ligaments)
Reticular fibers – thin, branching, support soft organs like the liver and spleen
Ground substance:
Gel-like material made of hyaluronic acid and proteins
Forms a moist, supportive matrix that surrounds and supports fibers and cells
Loose Connective & Adipose Tissue – Short Summary
Loose connective tissue:
Found between organs
Absorbs shock and binds tissues
Allows nutrients and fluids to diffuse to nearby cells
Adipose tissue:
Made of fat cells with little matrix and many capillaries
White fat: stores energy, insulates, cushions (e.g., around kidneys, eyes)
Brown fat: found in infants and some adult areas (neck/clavicle), burns fat for heat instead of ATP
Dense connective tissue has more
collagen fibers than loose connective tissue, making it stronger and more stretch-resistant.
Dense regular connective tissue:
Fibers run parallel → strong in one direction
Found in tendons and ligaments
Elastic version contains elastin, allowing stretch and recoil (e.g., vocal cords, spine ligaments)
Dense irregular connective tissue:
Fibers run in random directions → strong in all directions
Found in skin’s dermis and arterial walls, helping tissues stretch and return to shape
Supportive Connective Tissue –
Cartilage and bone support body structure and protect organs.
Cartilage
Made of chondrocytes in spaces called lacunae
Surrounded by perichondrium (dense connective tissue)
Avascular, so heals slowly
Types of Cartilage:
Hyaline cartilage: smooth, flexible, found in joints, nose, ribs, and fetal skeleton
Fibrocartilage: tough, with thick collagen fibers; found in knee menisci and spinal discs
Elastic cartilage: strong and stretchy; found in the external ear
Bone – Short Summary
Bone is the hardest connective tissue, providing support and protection.
Its matrix has collagen (for flexibility) and minerals like calcium phosphate (for strength).
Osteocytes (bone cells) sit in lacunae, arranged in rings around a central canal.
Bone is highly vascularized and heals faster than cartilage.
Types of Bone:
Cancellous (spongy) bone – lightweight with spaces; found inside bones and ends of long bones
Compact bone – dense and strong; provides most of the bone’s structure
Fluid Connective Tissue –
Blood and lymph are fluid connective tissues with cells in a liquid matrix.
Blood:
Made in bone marrow from stem cells
Contains:
Red blood cells (erythrocytes) – carry oxygen
White blood cells (leukocytes) – fight infections
Platelets – help with blood clotting
Transports nutrients, gases, and waste
Lymph:
Contains white blood cells in a clear fluid
Removes excess fluid and large molecules from tissues
Transports fats from the intestines to the bloodstream
Neuron (Nerve Cell)
Cell body (soma): contains nucleus and organelles
Dendrites: receive signals and send them to the soma
Axon: carries signals away from the cell to other cells
Myelin: insulating layer on axon (made by glial cells)
Synapse: gap between neurons where signals pass via neurotransmitters
Neuron Types:
Multipolar – many dendrites, one axon
Bipolar – one dendrite, one axon
Unipolar – one branch that splits into dendrite and axon
Neuroglia (Glial Cells)
-Support and protect neurons
Astrocytes – regulate ions, neurotransmitters, form blood-brain barrier
Microglia – act like immune cells, fight infection
Oligodendrocytes – make myelin in the CNS
Schwann cells – make myelin in the PNS
Directional Anatomical Terms –
These 10 terms help describe the location of body parts in relation to each other:
Anterior (ventral) – front (e.g., toes are anterior to the foot)
Posterior (dorsal) – back (e.g., the knee is posterior to the kneecap)
Superior (cranial) – above (e.g., eyes are superior to the mouth)
Inferior (caudal) – below (e.g., pelvis is inferior to the abdomen)
Lateral – toward the side (e.g., thumb is lateral to the fingers)
Medial – toward the middle (e.g., big toe is medial)
Proximal – closer to the body/trunk (e.g., upper arm is proximal to forearm)
Distal – farther from the body/trunk (e.g., shin is distal to the thigh)
Superficial – closer to the surface (e.g., skin is superficial to bones)
Deep – farther from the surface (e.g., brain is deep to the skull)
An anatomical plane is an imaginary line used to divide the body for viewing or scanning:
Sagittal plane – divides the body into left and right
-Midsagittal: equal halves
-Parasagittal: unequal halves
Frontal (coronal) plane – divides into front (anterior) and back (posterior)
Transverse plane – divides into top (upper) and bottom (lower); creates cross sections
Body Cavities – Short Summary
The body is organized into compartments that protect organs and allow movement.
Dorsal cavity (back): protects the brain and spinal cord
Ventral cavity (front): houses organs like the heart, lungs, stomach, and intestines
- Allows these organs to expand and contract during function without harming nearby tissues.
Body Cavity Subdivisions – Short Summary
Posterior (Dorsal) Cavity:
Cranial Cavity
Spinal Cavity
Anterior (ventral) Cavity:
Thoracic Cavity
Diaphragm
Abdominopelvic cavity (largest):
Abdominal cavity
Pelvic cavity
_______
- Posterior (Dorsal) Cavity:
Cranial cavity – contains the brain
Spinal cavity – contains the spinal cord
Both are protected by bones and cushioned by cerebrospinal fluid
- Anterior (Ventral) Cavity:
Thoracic cavity – houses heart and lungs, protected by rib cage
Diaphragm separates thoracic and abdominopelvic cavities
- Abdominopelvic cavity (largest):
Abdominal cavity – contains digestive organs
Pelvic cavity – contains reproductive organs
The peritoneal cavity can be divided two ways:
- Nine regions: uses two horizontal and two vertical lines (from mid-clavicles) for a detailed view.
- Four quadrants: a simpler method using one vertical and one horizontal line crossing at the navel (umbilicus); commonly used in medicine.
Serous Membranes – Short Summary
Serous membranes line body cavities and cover organs, forming fluid-filled sacs that reduce friction during organ movement.
Pleura – surrounds the lungs
Pericardium – surrounds the heart
Peritoneum – surrounds abdominal and pelvic organs
Each has two layers:
1.Parietal (lines cavity wall)
2. Visceral (covers organ)
Serous fluid between layers prevents friction and protects internal organs.
Homeostasis is
the body’s way of keeping internal conditions stable despite external changes.
It regulates variables like temperature, pH, ion levels, and oxygen.
Each variable has a set point range with normal limits (high and low).
The body must keep conditions within these limits to function properly.
Negative & Positive Feedback – Short Summary
Feedback loops help the body respond to changes and maintain balance:
Negative feedback: reverses the change to bring conditions back to normal (e.g., body temperature regulation)
Positive feedback: amplifies the change until the original stimulus is removed (e.g., childbirth contractions)
A negative feedback system has three main parts:
- Sensor (receptor) – detects a change in a physiological value
- Control center – compares it to the normal range and decides what to do
- Effector – makes a change to bring the value back to normal
A negative feedback system works to reverse changes and return the body to homeostasis.
🔄 Key Components (5 parts):
Stimulus – a change outside the normal range
Sensor – detects the change
Control center – processes info and decides action
Effector – carries out the correction
Response – brings value back to normal
🩸 Example: Blood Glucose Regulation
High blood sugar → sensed by pancreas (beta cells)
Insulin is released → tells muscle, fat, and liver to absorb glucose
As levels drop, insulin stops (negative feedback)
🌡️ Example: Body Temperature Regulation
If too hot:
Blood vessels dilate (heat radiates out)
Sweat increases (cooling through evaporation)
Breathing deepens (releases heat)
If too cold:
Blood flow reduces at skin
Shivering generates heat
Thyroid hormone and epinephrine raise metabolism for heat production
These processes keep body functions within a healthy range.
Positive feedback
amplifies a change instead of reversing it, moving the body further from normal until a specific end point is reached.
It’s only used in special situations like childbirth or blood loss.
Example: During childbirth, muscle contractions trigger more contractions until the baby is delivered.
Once the goal is reached, the feedback loop stops.
Transport Across the Cell Membrane – Short Summary
The cell membrane controls what enters and leaves the cell, helping regulate ions, nutrients, and wastes.
Its lipid bilayer has a nonpolar interior, making it selectively permeable:
1.Small, nonpolar substances (e.g. oxygen, CO₂, alcohol) pass easily
2.Water-soluble substances (e.g. glucose, amino acids, ions) need help
There are two main types of transport:
1.Passive transport – no energy needed; moves substances with the concentration gradient
2.Active transport – requires energy (ATP); moves substances against the gradient
Passive transport
moves substances across the cell membrane without energy, using concentration gradients.
Concentration gradient:
(passive transport)
difference in substance concentration across space
Substances move from high to low concentration (down the gradient)
Diffusion: particles spread out naturally until evenly distributed
🔄 Examples of Simple Diffusion:
Oxygen (O₂) moves into cells (higher outside)
Carbon dioxide (CO₂) moves out of cells (higher inside)
No energy is needed, just natural movement
🌡️ Higher temperatures speed up diffusion (e.g., body temp helps this process)
This process is crucial for gas exchange in the lungs and throughout the body.
Facilitated diffusion helps
large, polar, or charged molecules cross the cell membrane without energy.
These molecules cannot pass through the lipid bilayer on their own.
Instead, they move down their concentration gradient using protein channels or carriers.
💡 Example:
Glucose is too large and polar to pass through the membrane
A glucose transporter protein helps move it into the cell
This process is passive—it doesn’t require energy, just assistance.
Facilitated diffusion uses
membrane proteins to help large or charged molecules cross the cell membrane without energy.
Channel proteins: less selective, allow ions based on size/charge
Carrier proteins: more selective, allow specific molecules only
🔄 Examples:
Na⁺ ions move into cells through sodium channels
Glucose and amino acids enter cells via carrier proteins
Wastes may exit the cell this way
This process is passive and follows the concentration gradient.
Osmosis is
the passive movement of water across a semipermeable membrane from low solute concentration to high solute concentration.
💧 Water moves to balance solute levels:
Isotonic: Equal solute inside and outside → cell stays normal
Hypertonic: More solute outside → water leaves cell → cell shrinks
Hypotonic: More solute inside → water enters cell → cell swells or bursts
Maintaining an isotonic environment is key to cell health and is controlled by systems like the kidneys.
Filtration is
a passive transport method that uses pressure, not concentration, to move fluids and solutes.
Fluids move from high to low pressure across a membrane
Important in the circulatory system (nutrient delivery) and kidneys (waste removal)
Driven by hydrostatic pressure, not by concentration gradients
Active transport
moves substances against their concentration gradient (from low to high) and requires energy (ATP).
Uses protein pumps to transport molecules across the membrane
Unlike passive transport, ATP is needed to move substances
🔁 Example: Sodium-Potassium Pump (Na⁺/K⁺ ATPase)
Moves 3 Na⁺ out and 2 K⁺ in using 1 ATP
Maintains an electrical gradient (inside of the cell is more negative)
Essential in nerve cells, where it uses most of their ATP
🧬 Cell Transport:
How Things Move In and Out of Cells
Your body’s cells are like tiny bubbles. They need food, water, and oxygen to come in, and waste to go out. The outer layer of the cell (called the cell membrane) controls what moves in and out.
🧬 Cell Transport:
There are 2 main ways things move:
🚶♀️ 1. Passive Transport (No energy needed)
This is like rolling downhill—easy and doesn’t need energy.
✅ Diffusion
Things move from crowded places to less crowded places.
Example: Your cells use oxygen to make energy. Since there’s more oxygen in your blood than inside your cells, oxygen diffuses from the blood into your cells—no energy needed!
💧 Osmosis
This is when water moves across the cell membrane.
Water moves to where there’s more stuff (like salt) to try to balance it out.
🧃 Facilitated Diffusion
Some things are too big or charged to cross the cell on their own, like sugar or salt.
So the cell uses special doorways (proteins) to help them get through—still no energy needed.
💪 2. Active Transport (Needs energy)
This is like pushing uphill—it takes work and uses energy from the cell (called ATP).
Cells use protein pumps to move things from less crowded to more crowded places.
Example: In nerve cells, the sodium-potassium pump moves sodium out and potassium in to help send messages in your body.
🔼 What’s a Gradient?
A gradient means there’s a difference between two places.
If one side has more and the other has less, things move from more to less—that’s going with the gradient (easy).
Moving from less to more is against the gradient and takes energy.
The three types of diffusion are:
✅ Simple diffusion
✅ Facilitated diffusion
✅ Osmosis (diffusion of water)
What are connective tissue cells dispersed in?
Matrix
What are two types of connective tissue?
Loose connective tissue, dense connective tissue
Which type of tissue assists with the transport of fluid, nutrients, waste, and chemical messengers?
Connective tissue
What are the cells that are abundant in the central nervous system and have many functions, including the formation of the blood-brain barrier?
Astrocytes
Microglia
– Immune cells in the brain and spinal cord that protect against infections and clean up debris.
Dendrites
– Branch-like parts of a neuron that receive signals from other cells.
Axons
– Long fiber of a neuron that sends signals to other cells.
Which cell shapes are present in epithelial tissue?
Columnar
Cuboidal
Squamous
Where is stratified squamous epithelium commonly found?
In human skin
Simple squamous epithelial cells are found _________ and their function is to _______.
in the air sacs of lungs and lining of the heart; allow materials to pass through by diffusion and filtration
Where is simple cuboidal epithelium found, and what is its function?
In ducts and secretory portions of small glands and in the kidney tubules; secrete and absorb
Where is stratified cuboidal epithelium found, and what is its function?
In sweat glands, salivary glands, and mammary glands; protect tissues)
Where is stratified squamous epithelium found, and what is its function?
Lining the esophagus and mouth; provide protection against abrasions
Human Body Cavities – Quick Overview
Body cavities are spaces in the body that protect organs, allow movement, and organize internal structures. The two main cavities are:
- 🔙 Posterior (Dorsal) Cavity
Protects the central nervous system
Cranial cavity – holds the brain
Spinal (vertebral) cavity – holds the spinal cord
These are continuous and protected by bone and cerebrospinal fluid
- 🔜 Anterior (Ventral) Cavity
Larger and allows organ movement & expansion
Thoracic cavity – holds heart and lungs, protected by the rib cage
Includes the pleural cavities (lungs) and pericardial cavity (heart)
Diaphragm – separates thoracic and abdominal areas
Abdominopelvic cavity – holds digestive, reproductive, and urinary organs
Subdivided into:
1.Abdominal cavity – stomach, liver, intestines, etc.
2.Pelvic cavity – bladder, reproductive organs
💧 Serous Membranes
Line the cavities and reduce friction around organs:
Pleura (lungs)
Pericardium (heart)
Peritoneum (abdominal organs)
Let me know if you’d like this turned into a graphic or printable chart!
The body’s abdominal quadrants divide the abdomen into
four sections using one vertical and one horizontal line that cross at the navel (umbilicus).
These quadrants help doctors describe pain or problems in specific areas of the abdomen.
✅ The Four Quadrants:
1.Right Upper Quadrant (RUQ)
Liver, gallbladder, right kidney, parts of the small and large intestines
2.Left Upper Quadrant (LUQ)
Stomach, spleen, left kidney, pancreas, parts of the small and large intestines, (heart- technically, it is in the thoracic cavity, not the abdominal cavity.)
3.Right Lower Quadrant (RLQ)
Appendix, right ovary (in females), right ureter, parts of intestines, cecum
4.Left Lower Quadrant (LLQ)
Left ovary (in females), left ureter, parts of intestines,
✅ Descending colon
✅ Small intestine
✅ Sigmoid colon
What are the two largest human body cavities?
Dorsal and ventral
