Cell Biology Concepts Quiz

Anatomy and Physiology

• This course covers the structure and function of the human body for medical technologists
• Anatomy studies body structures and their relationships
• Physiology concerns the functions of body parts, and how they carry out life-sustaining processes
• These areas are inseparable
• The body is organized in a hierarchy from atoms to molecules to organelles to cells to tissues to organs to organ systems to organisms
• Homeostasis is important in maintaining a stable internal environment.
• Negative feedback mechanisms, common in maintaining homeostasis, are vital for regulating various functions in the body (e.g., temperature).
• Positive feedback mechanisms, less common, amplify a stimulus.
• This course covers multiple body systems
• The study also covers the basic anatomy and physiology of these systems.
• The study of specific organ systems is important to understand their operation

Branches of Science

• Anatomy
• Studies the bodies structures and the relationships between different parts of the body
• Body structures can be seen, felt, and examined closely
• Physiology
• Concerns the function of the body, and how the body parts work to carry out essential life functions
• Anatomy and physiology are inseparable
• The function of a structure reflects its structure

Anatomy

• Greek word "to cut apart"
• Broad field with many subdivisions
• Provides sufficient information for a course in itself
• Gross or macroscopic Anatomy
• Study of large body structures visible to the naked eye (Heart, lungs, kidneys)
• Regional Anatomy
• All of the structure of the body by body region (e.g., abdomen, leg)
• Systemic Anatomy
• Study of body structures by system by system (e.g. cardiovascular system, respiratory system)
• Surface Anatomy
• Internal structure relationship to the overlying skin surface
• Microscopic Anatomy
• Deals with the structures smaller than those seen with the naked eye (e.g., tissues, cells, components of the cells)
• Cytology, Histology
• Developmental Anatomy
• Structure changes throughout the life span

Physiology

• Operation of specific organ systems
• Renal Physiology
• Neurophysiology
• Cardiovascular physiology
• Focuses on events at the cellular or molecular levels
• Body’s abilities depend on its individual cells
• Ultimately depend on the chemical reaction occurring within them
• Rest on principles of physics

Complementarity of Structure and Function

• Anatomy and physiology are inseparable
• Function always reflects structure
• Key concept is the “Principle of complementarity of structure and function”

Levels of Structural Organization

• Chemical level
• Atom, molecule, organelles
• Cellular level
• Cells
• Tissue level
• Tissues
• Organ level
• Organs
• Organ system level
• Organ systems
• Organism level
• Organisms

Necessary for Life Function

• Nutrients
• Oxygen
• Water
• Normal body temperature
• Appropriate atmospheric pressure

Homeostasis

• Ability to maintain relatively stable internal conditions even though the outside world changes
• Homeostatic control is chiefly accomplished by the nervous and endocrine systems
• Information is carried via neural electrical impulses or blood-borne hormones

Three component

• Receptor : Sensor that monitors the internal environment and is responsible for stimuli
• Control Center : Determines the set point and analyzes the input
• Effector : Carries out the control center's response to the stimulus

Negative feedback mechanism

• Most homeostatic control mechanisms involve negative feedback.
• The output shuts off the original effect or reduces intensity.
• The variable changed in a direction opposite to the initial change, returning it to its "ideal" value.

Positive Feedback Mechanism

• The initial response of the stimulus enhances.
• The feedback mechanism is "positive" because the change proceeds in the same direction as the initial change, causing the variable to deviate further from its initial value/ range

Homeostatic Imbalance

• Homeostasis is so important that most disease can be regarded as a result of its disturbance.
• As we age, our body's control systems become less efficient, and our internal environment becomes less stable.
• Homeostatic imbalance occurs when the usual negative feedback mechanisms are overwhelmed, and destructive positive feedback mechanisms take over

Anatomical Position and Directional Terms

• Anatomical position: standing erect with feet slightly apart, palms facing forward
• Various directional terms are used to describe the location of body parts in relation to each other

Regional Terms

• Axial: head, neck, and trunk.
• Appendicular: appendages or limbs attached to the axis

Body planes and Sections

• Anatomical studies often cut or sectioned along a flat surface called a plane
• Sagittal, frontal, and transverse planes are common planes
• Sagittal plane: divides body into right and left structures
• A sagittal plane that lies at the exact midline is the median plane
• All other sagittal planes offset from the midline and are parasagittal planes
• Frontal plane/ Coronal Plane: divides the body into anterior and posterior structures
• Transverse plane/ Horizontal Plane: divides the body into superior and inferior structures
• Oblique sections are cuts made diagonally between the horizontal and vertical planes

Dorsal Body Cavity

• Protects the fragile nervious system organs
• Divided into the cranial cavity and vertebral cavity
• Cranial cavity: encases the brain
• Vertebral/spinal cavity: encloses the spinal cord
• Both cavities are continuous

Ventral Body Cavity

• More anterior and larger of the closed body cavities
• Two major subdivisions
• Thoracic cavity
• Surrounded by ribs and chest muscles
• Subdivided into the lateral pleural cavity, medial mediastinum And pericardial cavity
• Pericardial cavity encloses the heart
• Abdominal cavity
• Contains stomach, intestines, liver, and other organs
• Pelvic cavity
• Contains urinary bladder and reproductive organs and the rectum

Membranes in the Ventral Body Cavity

• The walls and outer surfaces of the ventral body cavity are covered by the thin, double-layered membrane
• Serosa or serous membrane
• The folds within the body cavity
• Visceral Serosa :covers the organs in the cavity
• Parietal serosa : covers the walls of the cavity
• The serous membranes are named for the specific cavity and organs with which they are associated

Abdominopelvic Regions and Quadrants

• It is divided into smaller regions to study the structures
• 9 regions, delineated by four planes
• 4 quadrants: right upper quadrant, right lower quadrant, left upper quadrant, left lower quadrant

Other Body Cavities

• Oral and digestive cavities
• Nasal cavity
• Orbital cavities
• Synovial cavities

Cell: Parts and Function

• The 100 trillion cells in a human being are living structures that can survive for months or years.
• The cells are the building blocks of the body
• They provide structure, ingest nutrients, convert them into energy, and perform specialized functions
• They also contain the body’s hereditary code which controls substances synthesized in the cells and enables them to make copies of themselves.

Organization of the Cell

• Nucleus & Cytoplasm
• Nucleus is separated from the cytoplasm by a nuclear membrane
• Cytoplasm is separated from the surrounding fluids by a cell membrane/ plasma membrane
• Protoplasm: The different substances collectively called the protoplasm
• Protoplasm is made up of water, electrolytes, proteins, lipids, and carbohydrates

Protoplasm: Substance that make up the cells

• Water: Principal fluid medium
• Ions: Important ions include potassium, magnesium, phosphate, sulfate, bicarbonate, and smaller quantities of sodium, chloride, and calcium
• Proteins: 2nd most abundant, divided into two types: structural proteins & functional proteins.
• Structural protein, mostly in the form of long filaments that function as the cytoskeleton
• Functional proteins, mostly as enzymes
• Lipids: Important lipids include phospholipids and cholesterol which form the cell membrane
• Carbohydrates: Play a major role in cellular nutrition.

Physical structure of the cell

Intracellular organelles

• Endoplasmic reticulum
• Golgi apparatus
• Mitochondria
• Lysosomes
• Peroxisomes
• Secretory vesicles

Membrane structures

• Most cell organelles are covered by membranes
• Cell membrane
• Nuclear membrane
• Endoplasmic reticulum
• Mitochondria
• Lysosomes
• Golgi apparatus

Cell Membrane

• Envelopes the cell
• Thinnest
• Composed mainly of proteins and lipids (55%, 25%, 13% respectively)
• Lipids: bilayer
• Proteins: interspersed, many, different types
• Carbohydrates: Attached to proteins and lipids on the outer surface of the cell membrane

Lipid Bilayer

• Thin double-layered film of phospholipids, cholesterol, and glycolipids over the whole cell surface.
• Phospholipids are the most abundant of the cell membrane lipids
• One end of each phospholipid molecule is soluble in water (hydrophilic), other isn’t (hydrophobic)
• The lipid layer in the middle of the membrane is impermeable to usual water-soluble substances, such as ions, glucose, and urea.
• Fat-soluble substances, such as oxygen, carbon dioxide, and alcohol, can penetrate this part of the membrane with ease.
• Sphingolipids have hydrophobic and hydrophilic end and are associated with nerve cells
• Cholesterol increases the fluidity and stability of the membrane

Membrane proteins

• Integral proteins: Protrude all the way through the membrane
• Peripheral proteins: Attached to one side of the membrane and not penetrate the membrane
• Channel proteins: Forms pores that allow water or water-soluble substances to diffuse between the intracellular and extracellular fluids. Their selective properties allow preferential diffusion
• Carrier proteins: Transport substances. Some in the direction opposite to their electrochemical gradient, called 'active transport’

Membrane carbohydrates

• Membrane carbohydrates occur almost invariably in combination with proteins or lipids in the form of glycoproteins or glycolipids.
• They protrude to the outside of the cell
• A loose carbohydrate coat called the glycocalyx is on the cell’s outer surface

Cytosol

• Jelly like fluid in the cytoplasm
• Cytosol & Organelles
• Neutral fat globules
• Glycogen granules
• Ribosomes
• Secretory vesicles
• Endoplasmic reticulum
• Golgi appartatus
• Mitochondria
• Lysosomes
• Peroxisomes

Endoplasmic Reticulum

• Network of tubular and flat vesicular structures
• Functions in preparing molecules made by the cell and transports them
• Lipid bilayer membranes that contain large amounts of protein.
• The total surface area is large, often 30-40 times the cell membrane area
• Endoplasmic matrix – watery medium inside the ER

Endoplasmic Reticulum (Ribosomes)

• Attached to the outer surface are large numbers of minute granular particles
• Involved in the synthesis of new protein molecules
• Granular endoplasmic reticulum contains ribosomes
• Agranular reticulum has no attached ribosomes
• Involved in the creation of lipid substances

Golgi Apparatus

• Closely related to the endoplasmic reticulum
• Composed of 4-plus stacked layers of thin, flat vesicles
• Prominent in secretory cells, located on the side that secretory substances are extruded
• The transported substances are then processed to become lysosomes, secretory vesicles, and other cytoplasmic components

Lysosomes

• Vesicular organelles form by breaking off from the Golgi apparatus
• Provide intracellular digestive system
• Digest damaged cellular structures, food particles, unwanted matter such as bacteria

Peroxisomes

• Similar physically to lysosomes, but they’re different in their formation, content, and function.
• Formed by self- replication from the smooth endoplasmic reticulum, containing oxidases rather than hydrolases
• Hydrogen peroxide is a highly oxidizing substance.
• Oxidases combine oxygen with hydrogen
• Catalase helps break down hydrogen peroxide to water and oxygen

Secretory Vesicles

• Almost all secretory substances formed by the endoplasmic reticulum and Golgi apparatus
• Are then released into the cytoplasm of secretory vesicles or secretory granules
• The proenzymes secrete later through the outer cell membrane into the pancreatic duct to become activated in the duodenum and perform digestive functions on food in the intestinal tract

Mitochondria

• "Powerhouses" of the cell
• Extracting energy from the nutrients of cellular functions
• Present in all areas, but the total number varies per cell
• Concentrated in areas of high energy metabolism
• Composed of two lipid bilayer membranes
• Outer and inner membranes
• Cristae is the inner membrane and folds
• Matrix is filled with enzymes necessary for extracting energy from nutrients (e.g., oxidative enzymes)
• Oxidative enzymes on the cristae cause the oxidation of nutrients forming carbon dioxide and water, releasing energy

Mitochondria

• The liberated energy is used to synthesize adenosine triphosphate (ATP)
• Mitochondria are self-replicative cells

Nucleus

• Control center of the cell
• Contains large quantities of DNA (comprising genes)
• Genes determine the characteristics of a cell’s proteins (including structural proteins), and intracellular enzymes that control cytoplasmic and nuclear activities
• Genes control and promote reproduction of the cell.

Nuclear membrane

• Nuclear envelope
• Two separate bilayer membranes
• The outer membrane is continuous with the endoplasmic reticulum of the cytoplasm
• The nuclear membrane is penetrated by numerous nuclear pores

Nucleoli and Formation of Ribosomes

• Nuclear structures called nucleoli
• Contain RNA and proteins
• Involved in the synthesis of ribosomes
• DNA genes in the chromosomes cause RNA synthesis to be stored in nucleoli
• Molecules of RNA from the nucleoli migrate to the cytoplasm to assemble ribosomes (important in protein formation)

Cell Cycle

• Series of changes a cell goes through from the time it is formed until it reproduces
• Interphase: Cell grows, and carries out its usual activities
• Cell division/Mitotic phase: The cell divides into two

Interphase

• Period from cell formation to cell division
• Metabolic phase or growth phase
• G1 (gap 1)
• G2 (gap 2)
• S (synthesis)
• G1, G2, are gap phases
• The Synthesis phase duplicates DNA
• Preparing cells for division

DNA Replication

• DNA must be replicated exactly prior to cell division
• This ensures identical copies are passed to each of the two resultant daughter cells
• Replication is simultaneously on several strands that continues until all the DNA has been replicated
• Sequence of DNA replication
• Uncoiling
• Separation
• Assembly
• Restoration

Mitosis

• Four Phases
• Prophase
• Metaphase
• Anaphase
• Telophase

Cytokinesis

• Division of cytoplasm
• Begins during late anaphase and continues throughout telophase
• Contractile ring of actin microfilaments forms cleavage furrow and pinches cells apart

Control of Cell Division

• Regulated by internal and external factors (e.g., ratio of cell surface area to cell volume, chemical signals such as growth factors and hormones)
• Cells stop proliferating when they touch each other

Restriction point/G1 checkpoint

• Cyclin-dependent kinases (Cdks) - Crucial to the cell’s ability to complete synthesis, and enter mitosis
• Cdk activates and deactivates by cyclin

Endoplasmic Reticulum (ER)

• Synthesis of cellular structures
• Many products created here are transported to the Golgi apparatus
• Lipid synthesis occurs in the smooth ER
• Protein synthesis happens in the rough ER

Golgi Apparatus in synthesis of Cellular structures

• Provide additional processing of substances
• Synthesizes some carbohydrates (e.g., chondroitin sulfate and hyaluronic acid)

Processing of endoplasmic secretions

• Incoming vesicles contain digestive enzymes
• Modifies lipids and proteins
• The Golgi apparatus takes proteins from the ER and sorts and packages them in vesicles
• Vesicles transport lipids and other substances

Function of the Golgi Apparatus

• Intracellular vesicles from the Golgi apparatus fuse with the cell membranes
• The increased expansion of membranes replenishes the membranes as they are utilized

Mitochondria Extract Energy from Nutrients

• The principal substances (carbohydrates, fats, and proteins) from which cells extract energy chemically react with oxygen.
• Carbohydrates convert to glucose and proteins convert to amino acids, and fats convert into fatty acids
• These molecules undergo a sequence of reactions within the mitochondria called the citric acid cycle and Krebs cycle. This process split into component parts, producing hydrogen atoms and carbon dioxide.
• Hydrogen atoms combines with oxygen to release an amount of energy that’s used for converting ADP to ATP
• ATP is transported into all parts of the cell’s cytoplasm.

Uses of ATP for Cellular Functions

• Three major categories of cellular functions
• Transport of substances
• Synthesis of chemical compound
• Mechanical work • Cellular energy

Functional Movement of Cells

• Amoeboid locomotion
• Ciliary Movement

Amoeboid Movement

• Movement of entire cells relative to the surrounding
• Begins with protrusion of a pseudopodium
• The pseudopodium projects from one end of the cell, partially secures itself in the tissue area, and then the remainder of the cell is pulled towards the pseudopodium
• It requires specific proteins and energy
• The cells use a moderate, to large amount of actin protein
• Actin polymerizes to form a filamentous network that contracts once they bind to other actin-binding proteins (e.g. myosin)
• The process is energized because of high energy compound ATP.

Amoeboid Movement

• Results from continual formation of new cell membrane at the leading edge of the pseudopodium and the absorption of the membrane in the middle and rear

Amoeboid movement

• Attachment of pseudopodium to the surrounding tissue
• The attachment, is effected by receptor proteins that lines the inside of exocytosis vesicles
• The vesicles open allowing its inner to the outer and attach to ligands in its surrounding tissue
• The process requires ATP, and calcium ions

Amoeboid Movement

• Chemotaxis- important initiator of ameboid locomotion
• Occurs when certain chemical substances are present in tissues. Results in a characteristic movement that’s oriented, either towards or from the chemical stimulus. (chemoattractants or chemorepellents).

Amoeboid-movement

• Positive chemotaxis is the movement towards the source of a chemotactic substance, from an area of lower concentration towards a region of higher concentration
• Negative chemotaxis is when cells move away from the chemotactic substance.

Locomotion of cells: Ciliary Movements

• Locomotion produced by whip-like movement of cilia
• Occurs primarily in the surface of respiratory airways and inside the surface of the uterine tubes.
• Short pointed hair-like projections found on the surface of the cells
• Supported by microtubules, part of the structure that lie beneath the surface membrane (basal body)

Locomotion of cells: Ciliary Movements

• Whip-like motion of cilia moves mucus in the respiratory airway
• The movement of mucus is from the ostium toward the pharynx
• The slow movement of cilia in the uterine tube helps move the ovum from the ovary to the uterus

Locomotion of cells: Flagellary Movements

• Essentially the same structure as cilia
• Flagellum is much longer and moves in quasi-sinusoidal waves instead of cilia’s whip-like movements

End of Lecture

• Summary of the cells and their functions

Transport of substances through the cell membrane

• Differences in extracellular and intracellular concentrations and their importance
• Lipid barrier and the proteins that transport substances through the cell membrane
• Two basic processes: diffusion, and active transport

Osmosis

• Net movement of water across the selectively permeable membrane due to differences in water concentration
• Osmotic pressure
• Importance of Number of Osmotic Particles (Molar Concentration)

Active Transport

• Transport process that moves molecules or ions against a concentration gradient against an energy gradient (e.g., from an area of lower concentration to higher concentration.)
• Two types: primary and secondary active transport

Primary Active Transport

• Sodium/Potassium Pump (Na+-K+) : Transports Na+ out and K+ into the cell using ATP
• Calcium pumps: Maintain a low Ca2+ concentration within the cell by moving Ca2+ outwards through membrane
• Hydrogen pumps: Important in some cells that secrete acid and in maintaining pH homeostasis

Primary Active Transport

• Several important proteins involved.
• Carrier Protein (e.g., Na+-K+ pump)
• Function is still unknown.
• Contains three receptor sites for sodium ions and two for potassium ions.
• Inside portion near the sodium site has ATPase activity that becomes activated when two potassium ions bind to the outside and three sodium ions bind to the inside

Primary Active Transport

• The liberated energy causes a chemical and conformational change in the protein that extrudes the three sodium ions and two potassium ions into their respective areas

Primary Active Transport

• The Na+-K+ ATPase pump can run in reverse if the electrochemical gradients is stronger than the chemical energy
• This moves down the ion concentration gradients through the pump
• Creates ATP

Secondary Active Transport/Counter transport

• The energy is derived secondarily from energy related to ionic concentrations produced from earlier primary active transport
• Co-Transport: The energy of the sodium diffusing into the cell can be used to move another substance
• Counter-Transport: The energy of the sodium ion moving into the cell causes the other molecule to move out of the cell

Active Transport Through Cellular Sheets

• Active transport process may occur to substances through membrane in the cell on one side
• Followed by simple or facilitated diffusion through the membrane on the other

Cell Cycle

• Series of changes a cell goes through from its formation to reproduction
• Two major periods
• Interphase
• Cell division (Mitotic phase)

Interphase

• G1 (gap 1) phase: Cell grows and carries out its normal functions
• S (synthesis) phase: DNA replication
• G2 (gap 2) phase: The cell further prepares for division.
• Enzymes and other proteins are synthesized, and are then moved to their proper site

DNA Replication

• DNA must be replicated exactly before cell division to ensure each daughter cell gets identical copies.
• Begin simultaneously on several threads
• Continues until all DNA is replicated

DNA Replication

• Uncoiling, separation, assembly, and restoration of DNA

Mitosis

• Prophase: The chromatin coils and condenses; the nucleolus disappear; microtubules lengthen
• Metaphase: The chromosomes cluster at the midline of the cell midway between the poles. Their centromeres align precisely at the spindle equator
• Anaphase: The shortest phase-centromeres of the chromosomes split simultaneously and the two chromatids of each duplicated chromosome separate as the chromosomes are pulled to opposite poles.
• Telophase: The chromosomes uncoil and resume their threadlike chromatin form. A new nuclear envelope forms around each chromatin mass, the nucleolus reappears, and the spindle breaks down.
• Cytokinesis: The cleavage furrow pinches the cytoplasmic mass into two, which yields two daughter cells

RNA

• Decoding and messenger function
• Single stranded
• Ribosomes, consisting of two subunits
• mRNA, tRNA, rRNA

Protein Synthesis

• Two major steps: transcription and translation
• Transcription: The information specified in a DNA sequence is copied into an RNA sequence
• Different forms, essentially, to convey the identical information
• Transcription factors stimulate histones at the gene transcription site to loosen and bind to the promoter, specifying which DNA strand will serve as the template strand, RNA polymerase initiates transcription

Protein Synthesis

• Three basic phases of Transcription: 1. Initiation, 2. Elongation, 3. Termination
• Initiation: RNA polymerase binds to the promoter, DNA strands separate, initiates mRNA synthesis
• Elongation: RNA polymerase moves along the template strand, joins complementary nucleotides
• Termination: Stops when the polymerase reaches a special termination signal, RNA polymerase and the complete mRNA transcript are released

Translation

• The language of nucleic acids is translated into the language of proteins
• Genetic code: the base sequence of a gene is translated into its amino acid sequence
• Codons: correspond to three-base sequence on mRNA
• Stop codon: out of 64 codons, three signals stop
• Translation involves tRNA, the ribosomes, and mRNA

Role of tRNA (transfer RNA)

• Shape like a handheld drill that transfers amino acids
• Binds to mRNA codon
• Amino acid is from the cytoplasmic pool
• Anticodon on the other end

Translation

• Translation occurs in the cytosol
• Each phrase of translation requires energy and specific factors and enzymes

Translation

• Phases of translation
• Initiation- The small subunit binds to mRNA, a special methionine-carrying initiator tRNA, and then to the new mRNA
• Elongation- Amino acids are added
• Termination- The ribosome encounters a stop codon (signals the end of translation)

Tissue

• Groups of similar cells perform a shared function
• Four primary tissue types: epithelial, connective, muscle, and nervous tissue
• Epithelial tissues: cover and line body surfaces and cavities. Secrete and excrete fluids.
• Connective tissues: support, connect, and anchor.
• Muscle tissues: produce movement via contraction and/or relaxation
• Nervous tissues: send and receive signals (communication within the body).

Epithelial Tissue

• Sheet-like layers of cells
• Covering and lining (e.g., the outermost layer of the skin)
• Glandular (e.g., glands that secrete various substances)
• Functions: protection, filtration, excretion, secretion, and sensation
• Polarity- Apical surface (outermost, exposed part) and basal surface (attaches to underlying connective tissue).
• Specialized contacts- Tight junctions and desmosomes connect adjacent cells to form tissues.
• Supported by connective tissue- Basement membrane reinforces the sheet
• Avascular but innervated
• High regenerative capacity

Epithelial Tissue

• Two types of classification:
• Number of cell layers- Simple (one layer), Stratified (multiple layers)
• Shape of cells- Squamous (flat), Cuboidal (cube-shaped), Columnar (column-shaped)

Simple Epithelial

• Single layer of cells
• Involved in secretion, absorption, and filtration

Simple Squamous Epithelium

• Forms filtration membranes
• Lines the air sacs of the lungs
• Forms the walls of capillaries and lymphatic vessels

Simple Cuboidal Epithelium

• Forms the walls of the smallest ducts of glands and many kidney tubules

Simple Columnar Epithelium

• Most concerned with secretion and absorption
• Has modifications such as dense microvilli and tubular glands, which enhances its absorption and digestion

Pseudostratified Columnar Epithelium

• Appearance of multiple layers, not true multiple layers involved in secretion and excretion

Stratified Epithelium

• Contains two or more cell layers
• Regenerate from below, helping to protect deeper tissues

Stratified Squamous Epithelium

• Thick layers of cells
• Exposed surface cells are flattened (squamous)
• Keratinized epidermis
• Non-keratinized epidermis

Stratified Cuboidal Epithelium

• Rare in the body
• Found in the larger gland ducts

Stratified Columnar Epithelium

• Found in pharynx, male urethra, and some larger gland ducts
• Occurs at transition areas between other types of epithelia

Transitional Epithelium

• Forms the lining of hollow urinary organs
• Stretches as needed, which is important for their function.

Glandular Epithelium

• Secrete products onto body surfaces or into body cavities
• Classified: according to where they release products - Endocrine (internally secreting) or Exocrine (externally secreting)
• Number of cells- Unicellular (e.g., mucus cells and goblet cells) or Multicellular (e.g., multicellular glands)

Connective Tissue

• Most abundant and widely distributed
• Four Major Classes
• Connective Tissue Proper
• Cartilage
• Bone
• Blood
• Two Characteristics
• Extracellular Matrix
• Common origin from mesenchyme (embryonic tissue) -Three components: 1. Ground substance, 2. Fibers (collagen, elastic, reticular), 3. Cells
• Specialized cells according to generalized connective tissue
  • Blast cells (immature)
  • Cyte cells (mature)

Loose Connective Tissue

• Areolar Tissue
• Adipose Tissue
• Reticular Tissue

Areolar Tissue

• Universal packing tissue between other tissues
• Provide support and binding of other tissues and holds body fluids.
• Defend against infections, stores nutrients
• Found throughout the body, underlying almost all epithelia, and packages organs

Adipose Tissue

• Similar to Areolar tissue but nutrients storing ability is greater
• Large, closely packed cells called adipocytes.
• Oil droplets occupy most of cell volume, and the nucleus is displaced towards the edge
• Serves as energy reserve, thermal insulation, and protective cushion

Reticular Connective Tissue

• Network of reticular fibers along which fibroblasts are located
• It forms a loose internal network that supports free blood cells and other cells within lymphatic organs such as the lymph nodes, spleen, and bone marrow

Dense Connective Tissue

• The dense connective consist of three varieties
• Regular connective tissue
• Irregular connective tissue
• Elastic connective tissue

Dense Regular Connective Tissue

• Closely packed bundles run in the same direction
• Found in tendons and ligaments

Dense Irregular Connective Tissue

• Thick bundles are interwoven in all directions
• Found in the skin as the leathery dermis, fibrous joint capsules and fibrous coverings around some organs

Elastic Connective Tissue

• High proportion of elastic fibers
• Found in structures that need to stretch and recoil often (e.g., walls of large arteries and some ligaments)

Cartilage

• Stands up to both tension and compression
• Lacks nerve fibers and is avascular
• Three types:
• Hyaline cartilage
• Elastic cartilage
• Fibrocartilage

Hyaline Cartilage

• Abundant in the body
• Provides firm support with some flexibility
• Found in ribs, nose, trachea, and covers ends of long bones

Elastic Cartilage

• Contains many more elastic fibers than hyaline cartilage
• Found in structures needing strength and exceptional stretch ability (e.g., external ear and epiglottis)

Fibrocartilage

• Thick collagen fibers
• Resists compression and tension
• Found in intervertebral discs and the spongy cartilages of knees

Bone (Osseous Tissue)

• Provides body support and protection
• Stores fat and synthesizes blood cells
• More abundant collagen fibers and inorganic calcium salts
• Osteoblasts produce organic portion of matrix
• Osteocytes reside in lacunae

Blood

• Fluid connective tissue
• Surrounded by a fluid matrix called blood plasma
• Transports oxygen, carbon dioxide, nutrients, wastes, and other substances throughout the body

Muscle Tissue

• Well-vascularized tissues and responsible for most types of body movement
• Cells possess myofilaments (actin and myosin).
• Three kinds: skeletal, cardiac, smooth
• Two types: voluntary and involuntary muscle

Skeletal Muscle

• Attached to the bones of the skeleton
• Forms the flesh of the body
• Responsible for body movement, has elongated cylinders cells and visible striations

Cardiac Muscle

• Found only in the walls of the heart
• Cells are branching and interwoven; uninucleated, and separated by junctions called intercalated discs

Smooth Muscle

• Found in the walls of hollow organs (e.g., digestive and urinary tracts, uterus)
• Spindle-shaped, uninucleated cells, no striations
• Responsible for contractions and squeezing substances through these organs

Nervous Tissue

• Regulates and controls body functions
• Two major cells: neurons (highly specialized, branching cells), and supporting cells (glial/ neuroglial--non-conducting)

The Integumentary System

• Skin
• Covering the entire body with two distinct layers a. Epidermis : non-vascularized, outermost protective shield of the body, composed of epithelial cells, composed of 4-5 layers of keratinocytes b. Dermis: underlies the skin which is a tough, leathery layer mostly composed of dense connective tissue

Subcutaneous Tissue

• Deep to the skin
• A type of connective tissue, mostly adipose (fat), storing fat for cushion and insulation

Appendages of the Skin

• Hair
• Nails
• Sweat glands a.Eccrine : most numerous sweat glands, secrete a watery, hypotonic filtrate, plays a major role in body temp. regulation b. Apocrine : larger sweat glands, begin functioning at puberty, little role in temperature regulation, primarily involved in body odor c. Sebaceous oil glands: secrete sebum onto hair and skin

Hair

• Function: Keeps mammals warm, senses insects, protects the head from physical damage, filters particles from air
• Structure: 1. Shaft, 2. Root, 3. Hair Bulb, 4. Hair Papilla

Nails

• Protective covering on the dorsal surface of a finger or toe
• Made of hard keratin and found on fingers and toes, a. Proximal root b. Nail plate/body c. Free edge

Test your knowledge on key cell biology concepts including ligand functions, diffusion types, and organelle roles. This quiz covers various cellular processes and the functions of different cell organelles, helping you solidify your understanding of cell structure and function.