• Basic unit of all multicellular organisms
• Smallest structural unit producing all vital
functions
• Pre-existing cells produce cells
• Cell Membrane
• Cytosol
• Organelles
• Inclusions
Structure of a Generalized Cell
Figure 3.2
1
• Physical isolation: Extra/intracellular
barrier
• Regulation of exchange
• Sensitivity:Affected by changes in
extracellular fluid; receptors for recognition
and communication; alterations affect
physiology
• Structural support
• Diffusion
• Osmosis
• Filtration-Hydrostatic pressure forces water
across membrane; solutes selected
according to size.
• Facilitated diffusion
• Active transport-Na, K, Ca, Mg
• Endocytosis-phagocytosis, pinocytosis
2
Clathrin-Mediated Endocytosis
Figure 3.13
• Selectively permeable:
hypertonic
isotonic
hypotonic
• The cellular material between the plasma
membrane and nucleus;site of most
cellular activities.
• EM has revealed that it consists of cytosol,
organelles, and inclusion bodies.
3
Structure of a Generalized Cell
Figure 3.2
•
•
•
•
•
•
Viscous, semitransparent fluid substance
Complex mixture of salts
Dissolved proteins (enzymes)
Amino acids
Lipids
Low carbohydrate [ ]
• Non functional units/chemical substances
• Glycosomes-hepato and myocytes
• Lipids-adipocytes
4
• Specialized cellular compartments
• Non membranous- cytoskeleton, centrioles,
ribosomes, cilia, and flagella.
• Membranous- mitochondria, peroxisomes,
lysosomes, nucleus,endoplasmic reticulum,
and Golgi apparatus.
• Intracellular network that supports cell’s
structures & providing machinery to
generate various cell movements
• Four major components:microtubules,
microfilaments, intermediate, and thick
filaments.
• Thinnest elements of the cytoskeleton
• Primary protein: actin
• Forms dense cross-linked network under
cell membrane
• Involved in motility or changes in cell’s
morphology.
5
• Anchors cytoskeleton to integral proteins.
• Adheres cell membrane to underlying
cytoplasm.
• Responsible for amoebid movements and
membrane changes accompanying
endo/exocytosis.
• Elements with largest diameter; spherical
protein subunits (tubulin);determine cell’s
overall morphology and organelle
distribution.
• Functions as primary component of
cytoskeleton/anchor organelles; can adhere
to organelles for intracellular movement
• Form structural component of cilia,
flagella, and centrioles.
• Motor proteins (kinesins & dyneins) are
mainly responsible for repositioning of
organelles along microtubules.
6
Motor Molecules
Figure 3.25a
• Microscopic, finger-shaped projections of
membrane; increase surface area
(absorption) (jejunum/ileum, kidneys).
• Small, barrel shaped oriented at right angles
to each other (nine triplets); evident during
cell division; form bases; lacking in
osteocytes/mature RBCs
• Contain nine groups of microtubule
doublets surrounding central pair (9+2)
• Basal body anchor
• Exposed aspect of cilia covered by
membrane and “beat” rhythmically
• Propel substances across cell surface
• Substantially longer projections
• Propels cell
7
Cilia
Figure 3.27a
Cilia
Figure 3.27c
• Small, dark staining granules composed of
ribosomal RNA
• Two globular subunits (small, large)
• Free ribosomes produce soluble proteins
that will function in the cytosol
• Membrane-bound (fixed) ribosomes
synthesize proteins destined for cellular
membranes or cellular export.
8
•
•
•
•
•
Threadlike, double membraned organelle
Inner membrane forms cristae (ATP)
Number may vary according to cell type
DNA/RNA
Cellular respiration
Mitochondria
Figure 3.17
9
• Gene containing control center
• Controls synthesis of proteins
• Numbers vary: (osteoclasts, hepatocytes,
myocytes, RBCs)
• Shapes vary: spherical,elongate
• Has three distinct regions: nuclear
envelope, nucleoli, and chromatin.
• Dark staining spherical bodies located
within nucleus responsible for ribosomal
production
• Non-membrane bound
• Typically one or two per cell
• Subunits assembled
10
Nucleus
Figure 3.28a
• Composed of equal amounts of DNA and
globular histone proteins
• Chromosome-condensed chromatin coils
forming short “barlike” bodies.
• Network of intracellular membranes and
cisternae
• Functions: (1) Synthesizes carbohydrates,
lipids, and proteins; (2) Transportation
11
• Manufactures secreted proteins
• Continuum of RER
• Lipid metabolism and synthesis/cholesterolsteroid synthesis
• Absorption/transport lipids-detoxification
Figure 3.18a and c
• Principal “traffic director” for cellular
proteins
• Modifies, concentrates, and packages
• “Receiving” side is cis face, “shipping” side
is trans face
• Secretory vesicles pinch off from trans face
and fuse to membrane.
12
• Digests particles taken in by endocytosis
• Degrade worn-out or nonfunctional
organelles/break down nonuseful tissues
• Metabolic functions: glycogenolysis;
releasing of ThyH from thyroid cells
• Breakdown of bone to release Ca ions
Role of the Golgi Apparatus
Figure 3.21
• Membranous sacs containing powerful
enzymes(oxidases/catalases)
• Oxidases use O2 to detoxify alcohol and
formaldehyde
• Numerous in hepatocytes and kidney cells
• Self replicating/do not arise from Golgi
apparatus
13
• Tissues are groups of cells w/common and
related functions.
• Primary tissue types:
Epithelial(covering),Connective(support),
Muscle(movement), Neural(control).
• Occurs in the body as:
Covering, lining, glandular epithelium
• Functions include:
Protection, absorption, filtration,secretion.
• Composed of close packed cells; tiny
amount of extra-cellular material in narrow
spaces between them.
• Specialized contacts-Form continuous
sheets; junctions
• Apical surface, lateral, base
14
• Number of layers: Simple(single cell)
layer for absorption, filtration, & thin
barrier. Stratified (two or more)layers
common in high abrasion areas.
• Shape: Squamous, Cuboidal, Columnar
• Simple Squamous- Cells laterally flattened;
located in areas of filtration/rapid diffusion.
Endothelial lining-provides frictionless
lining; blood vessels/heart chambers.
• Simple Cuboidal-Spherical nuclei;
absorption & secretion; kidney tubules and
secretory ducts.
• Simple Columnar-Single layer of tall cells
aligned in rows;some have cilia;absorption
& secretion.
• Pseudostratified Columnar- Cells vary in
height; absorption & secretion; trachea.
15
• Stratified Squamous- Most widespread (in areas
of wear and tear);superficial cells less viable than
deep cells.
• Stratified Columnar- Rare tissue; forms large
gland ducts
• Transitional- Basal cells are cuboidal/colum.,
apical cells vary in shape according to distension
of organ; urinary bladder.
Classification of Epithelia
• Simple
or
stratifie
d
Figure 4.1a
Classification of Epithelia
• Squamous,
cuboidal, or
columnar
Figure 4.1b
16
• Found throughout entire body but never
exposed.
• Classes : (1)Connective tissue proper
(2)cartilage (3)bone (4) blood.
• Functions: (1)binding/support (2)
protection (3) insulation (4) transportation.
• Have common origin
• Varying degrees of vascularity
• Extracellular matrix: separates living from
non-living material; bears weight,
withstands tension,& endures physical
trauma.
• Loose Connective Tissue
Areolar- Most widely distributed CT;
supports and binds other tissues,reinforces
organs, stores nutrients.
Adipose- Adipocytes predominate(90%),
oil droplet occupies cell volume displacing
nuclei; tissue vascularized; insulation &
shock absorber.
17
Connective Tissue Proper: Loose
Figure 4.8c
• DENSE CONNECTIVE TISSUE
Dense regular-Parallel collagen fibers/ poorly
vascularized; enormous tensile strength; found in
tendons, ligaments.
Dense irregular:Irregularly arranged collagen
fibers, found in dermis, fibrous coverings of
kidneys, bones, cartilages, muscles, and nerves.
Connective Tissue Proper: Loose
Figure 4.8c
18
Connective Tissue Proper: Dense
Regular
Figure 4.8e
Connective Tissue Proper: Dense
Regular
Figure 4.8f
Cartilage
• Chondroitin sulfate
• Withstands tension & compression
• Flexible, avascular and lacks nerve fibers.
• Predominant cell types: chondroblasts,
chondrocytes.
19
Hyaline Cartilage
• Most abundant cartilage.
• Chondrocytes (1-10%) of cartilage vol.
• Located in nose, costal cartilages, tracheal
rings,larynx, embryonic skeleton, and
epiphyseal plates.
Elastic Cartilage
• Similar to hyaline; elastin fibers
• External ear and epiglottis
Fibrocartilage
• Matrix dominated by densely interwoven collagen
fibers
• Compressible & tension resistant.
• Intervertebral discs,pubic symphysis, meniscus.
Bone (Osseous tissue)
• Bone matrix similar to cartilage; more collagen
fibers & inorganic salts (hydroxyapatites)
• Supports/ protects softer tissue;
hematopoietic;vascularized
• Osteoblasts, osteocytes
Connective Tissue: Hyaline
Cartilage
Figure 4.8g
20
Connective Tissue: Elastic
Cartilage
• Similar to hyaline cartilage but with more
elastic fibers
• Maintains shape and structure while
allowing flexibility
• Supports external ear (pinna) and the
epiglottis
Figure 4.8h
Connective Tissue: Fibrocartilage
Cartilage
• Matrix similar to hyaline cartilage but less
firm with thick collagen fibers
• Provides tensile strength and absorbs
compression shock
• Found in intervertebral discs, the pubic
symphysis, and in discs of the knee joint
Figure 4.8i
• Blood
• Matrix: H20, salts, proteins (blood fibers
evident during clotting)
• RBCs, leukocytes, platelets
• Transportation
21
Connective Tissue: Blood
Figure 4.8k
• Highly cellular
• Vascularized
• Myofilaments (actin/myosin)
• Skeletal (striated), cardiac, smooth
Skeletal muscle
• Striated
• Attached to bones
• Somatic movements
• Large multinucleated myocytes
• Satellite cells-regenerative properties
22
Muscle Tissue: Skeletal
• Long, cylindrical, multinucleate cells with
obvious striations
• Initiates and controls voluntary movement
• Found in skeletal muscles that attach to
bones or skin
Figure 4.11a
Cardiac muscle
•
•
•
•
Exclusive to contactile walls of heart
Contractions propel blood
Uninucleate; intercalated discs
Pacemaker cells establish regular rate of
contractions (involuntary)
Muscle Tissue: Cardiac
• Branching, striated, uninucleate cells
interdigitating at intercalated discs
• Propels blood into the circulation
• Found in the walls of the heart
Figure 4.11b
23
Smooth muscle
• Striations absent
• Spindle shaped/central nucleus.
• GI and urinary tract, uterus, blood vessels.
Contract via pacesetter cells
Muscle Tissue: Smooth
Figure 4.11c
Neurons-Specialized for conduction;longest
cells in body; poor regenerative properties.
• Soma
• Axon
• Dendrite
Neuroglia-Supportive framework for neural
tissue (regulate interstitial composition&
nutrient supply)
24
Nervous Tissue
Figure 4.10
25