Download Chapter 3 Cells

Chapter 3
Cells
• vary in size
• vary in shape
• measured in
micrometers
3-2
Cell Membrane
• outer limit of cell
• controls what moves in and out of cell
• selectively permeable
•phospholipid bilayer
• water-soluble “heads” form surfaces
• water-insoluble “tails” form interior
• permeable to lipid-soluble substances
• cholesterol stabilizes the membrane
• proteins
• receptors
• pores, channels, carriers
• enzymes
• CAMS
• self-markers
3-4
Cell Membrane
3-5
Intercellular Junctions
Tight junctions
• close space between cells
• located among cells that form
linings
Desmosomes
• form “spot welds” between cells
• located among outer skin cells
Gap junctions
• tubular channels between cells
• located in cardiac muscle cells
3-6
Cell Adhesion Molecules
• guide cells on the move
• selectin – allows white blood
cells to “anchor”
• integrin – guides white blood
cells through capillary walls
• important for growth of
embryonic tissue
• important for growth of nerve
cells
3-7
Cytoplasmic Organelles
Endoplasmic Reticulum
• connected, membrane-bound
sacs, canals, and vesicles
• transport system
• rough ER
• studded with ribosomes
• protein and lipid synthesis
• smooth ER
• lipid synthesis
• break down of drugs
Ribosomes
• free floating or connected to ER
• site of protein synthesis
3-8
Cytoplasmic Organelles
Golgi apparatus
• group of flattened,
membranous sacs
• packages and modifies
proteins
Mitochondria
• membranous sacs with
inner partitions
• generate energy
3-9
Cytoplasmic Organelles
Lysosomes
• enzyme-containing
sacs
• digest worn out cell
parts or unwanted
substances
Peroxisomes
• enzyme-containing
sacs
• break down organic
molecules
Centrosome
• two rod-like centrioles
• used to produce cilia
• distributes chromosomes
during cell division
3-10
Cytoplasmic Organelles
Cilia
• short hair-like projections
• propel substances on cell
surface
Flagellum
• long tail-like projection
• provides motility to sperm
3-11
Cytoplasmic Organelles
Vesicles
• membranous sacs
• store substances
Microfilaments and microtubules
• thin rods and tubules
• support cytoplasm
• allows for movement of
organelles
3-12
Cell Nucleus
• control center of cell
• nuclear envelope
• porous double membrane
• separates nucleoplasm from
cytoplasm
• nucleolus
• dense collection of RNA and
proteins
• site of ribosome production
• chromatin
• fibers of DNA and proteins
• stores information for synthesis of
proteins
3-13
Movements Into and
Out of the Cell
Passive (Physical) Processes
• require no cellular
energy
• simple diffusion
• facilitated diffusion
• osmosis
• filtration
Active (Physiological) Processes
• require cellular energy
• active transport
• endocytosis
• exocytosis
• transcytosis
3-14
Simple Diffusion
• movement of substances from regions of higher concentration
to regions of lower concentration
• oxygen, carbon dioxide and lipid-soluble substances
3-15
Facilitated Diffusion
• diffusion across a membrane with the help of a channel or
carrier molecule
• glucose
3-16
Osmosis
• movement of water through a selectively permeable
membrane from regions of higher concentration to
regions of lower concentration
• water moves toward a higher concentration of
solutes
3-17
Osmosis
Osmotic Pressure – ability of osmosis to generate enough
pressure to move a volume of water
Osmotic pressure increases as the concentration of nonpermeable
solutes increases
• hypertonic – higher
osmotic pressure
• hypotonic – lower
osmotic pressure
• isotonic – same
osmotic pressure
3-18
Filtration
• smaller molecules are forced through porous membranes
• hydrostatic pressure important in the body
• molecules leaving blood capillaries
3-19
Active Transport
• carrier molecules transport substances across a membrane
from regions of lower concentration to regions of higher
concentration
• sugars, amino acids, sodium ions, potassium ions, etc.
3-20
Endocytosis
• cell engulfs a substance by forming a vesicle around the
substance
• three types
• pinocytosis – substance is mostly water
• phagocytosis – substance is a solid
• receptor-mediated endocytosis – requires the
substance to bind to a membrane-bound receptor
3-21
Endocytosis
3-22
Exocytosis
• reverse of endocytosis
• substances in a vesicle fuse with cell membrane
• contents released outside the cell
• release of neurotransmitters from nerve cells
3-23
Transcytosis
• endocytosis followed by exocytosis
• transports a substance rapidly through a cell
• HIV crossing a cell layer
3-24
The Cell Cycle
• series of changes a cell
undergoes from the time it forms
until the time it divides
• stages
• interphase
• mitosis
• cytoplasmic division
• differentiation
3-25
Interphase
• very active period
• cell grows
• cell maintains routine functions
• cell replicates genetic material to prepare for nuclear
division
• cell synthesizes new organelles to prepare for cytoplasmic
division
• phases
• G phases – cell grows and synthesizes structures other
than DNA
• S phase – cell replicates DNA
3-26
Mitosis
• produces two daughter cells from an original cell
• nucleus divides – karyonkinesis
• cytoplasm divides – cytokinesis
• stages
• prophase – chromosomes form; nuclear envelope
disappears
• metaphase – chromosomes align midway between
centrioles
• anaphase – chromosomes separate and move to
centrioles
• telophase – chromatin forms; nuclear envelope forms
3-27
Tumors
Two types of tumors
• benign – usually remains
localized
• malignant – invasive and can
metastasize; cancerous
Genes that cause cancer
• oncogenes – activate other
genes that increase cell division
• tumor suppressor gene –
normally regulate mitosis; if
inactivated they will not
regulate mitosis
3-31
Integumentary System
•
•
Integumentary system composed of two layers
and many different tissues.
Two distinct layers
1. Epidermis
a) Stratified keratinized squamous epithelium
2. Dermis
1.
2.
3.
4.
5.
Glandular epithelium (sweat, sebaceous glands)
Dense irregular connective tissue (collagen)
Smooth muscle tissue (arrector pili muscles)
Nervous tissue (Meissner’s & Pacinian corpuscles)
Blood vessels
Subcutaneous Layer
• Distinct layer beneath skin
• Composed of adipose tissue
• Provides insulation and protection
Layers of the Epidermis
• Stratum basale: deepest layer, single row of
cells that divide and grow
• Stratum spinosum: flat cells with keratin
• Stratum granulosum: flat keratinized cells
with shriveled nuclei
• Stratum lucidum: clear cells
• Stratum corneum: many layers of flat, dead,
keratinized, nonnucleated cells that are shed
Melanin
• Melanin is a dark
pigment produced
by melanocytes.
• Melanin absorbs
ultraviolet light
and helps prevent
mutations and
damage to cells.
Figure 6.4
Melanin
ABC’s of Melanoma
A. Asymmetry the shape of one side does not match
the other
B. Border ragged or irregular edges
C. Color color uneven, different shades of brown,
black, and tan
D. Diameter greater than 5mm or the size of an
eraser head
E. Elevation mole is raised or elevated above skin
Melanin
•
•
•
•
•
Determines skin color
Produced by melanocytes in basal layer
Everyone has same # of melanocytes
Inherit amount of melanin produced
Determines race and/or skin color
Skin Color
Besides melanin other factors affect skin
color:
1. Carotene yellow
2. Hemoglobin pink
3. Cyanosis blue
Dermis
• Epidermal (rete) ridges project into the dermis.
• These dermal papillae are responsible for
fingerprints.
• The dermis binds the epidermis to the underlying
tissues.
• Nourishment for epidermis
• The dermis is composed of irregular dense
connective tissue with collagen and elastin in a gellike ground substance.
Dermis
• Dermis contains muscle fibers. Smooth muscles
(arrector pili) are associated with follicles and glands.
• Motor and sensory nerves and sensory receptors are
found throughout the dermis.
– Meissner’s corpuscles light touch
– Pacinian corpuscles pressure sensors
• The dermis contains accessory organs such as blood
vessels, hair follicles, sebaceous and sweat glands.
Dermis’s Two Distinct Layers
A. Papillary dermis
1)
2)
3)
4)
Upper 20% immediately beneath epidermis
Loose areolar CT
Dermal papillae
Meissner’s corpuscles sensory receptor for
light touch
Dermis’s Two Distinct Layers
A. Reticular dermis
1) Lower 80%
2) Composition: dense irregular CT
a) Bundles of collagen, elastic, and reticular
b) Strength, resiliency, and elasticity
Subcutaneous Layer
• The subcutaneous layer or hypodermis is made
up of loose connective and adipose tissue.
• Collagenous and elastic fibers are continuous with
those in the dermis.
• The adipose tissue conserves body heat.
• The subcutaneous layer contains the major blood
vessels (rete cutaneum) that supply the skin.
Sebaceous Glands
• Sebaceous glands are holocrine glands associated
with hair follicles.
• Sweat glands or sudoriferous glands (sudor- Latin
sweat) are epithelial glands widespread in the skin.
• Sebum , a mixture of fatty material and cellular
debris, is secreted to keep hair and skin soft and
waterproof.
• Acne results from excess sebum secretion.
Sweat Glands
• Eccrine
glands
respond to
increased
body
temperature
and function
in
evaporative
cooling.
Figure 6.11
Skin Healing
• Superficial cuts heal due to increased
epithelial cell division.
• Dermal cuts involve clotting and scab
formation. Growth factors stimulate cell
division and growth and scars may form.
• Granulation tissue large wounds
Skin Functions
1. Protection – water loss, injury, chemicals
and bacteria
2. Excretion – minimal but urea and uric
acid are secreted in addition to electrolytes
3. Regulation – body temperature
Skin Functions
4. Sensation
a) Meissner’s corpuscles
i.
ii.
iii.
iv.
Light touch
Egg-shaped
Dermal papillae
Fingertips, palms, soles, eyelids, tip of tongue,
nipples, clitoris, and tip of penis
Skin Functions
4. Sensation (continued)
b) Pacinian corpuscles
i.
ii.
iii.
iv.
Pressure
Onion shaped
Deep dermis and subcutaneous
Joints, tendons, muscles, mammary glands, and
external genitalia
Skin Functions
5. Vitamin D synthesis
a) UV rays activate synthesis
b) critical in bone homeostasis
6. Blood reservoir 10% of body’s blood
vessels
7. Immunity
a) Langerhan’s cells
b) T-helper cells
Bone Classification
• Bones are classified according to shape
• Long bones are long with expanded ends, Ex:
forearm and thigh bone
• Short bones are cube like, Ex: wrist, ankle
• Flat bones are broad and plate like, Ex: ribs,
scapulae, and some skull bones
• Irregular bones vary in shape, Ex: vertebrae
• Sesamoid or round bones are small bones
embedded in tendons, Ex: kneecap (patella)
Parts of Bone
Figure 7.2
Compact Bone
• Osteocytes and layers of intercellular material lie
in concentric rings around an osteonic canal.
• This unit is called an osteon or Haversian system.
• Osteonic canals contain blood vessels and nerve
fibers and are interconnected by transverse
perforating (Volkmann’s) canals.
• Intercellular material made of collagen and
inorganic salts.
Spongy Bone
•
•
•
•
•
•
Cancellous bone
Partially fills medullary space/cavity
Red or yellow
Yellow – fat
Red – marrow
Bone spicules - trabeculae
Bone Growth and Development
• The skeletal system begins to form during
the first weeks of prenatal development.
• Some bones originate within sheets of
connective tissue (intramembranous
bones).
• Some bones begin as models of hyaline
cartilage that are replaced by bone
(endochrondral bones).
Intramembranous Bones
• Broad, flat skull bones are intramembranous
bones.
• During osteogenesis layers of primitive,
connective tissue supplied with blood
vessels appear at the site of future bone.
Intramembranous Bones
• Cells differentiate into osteoblasts (bone-building
cells) which deposit spongy bone.
• Boney mineral matrix laid down around
osteoblasts made by osteoblasts.
• Spongy bone forms in all directions around
osteoblasts.
• Osteoblasts become osteocytes when surrounded
by bony matrix in lacunae.
• Later some spongy bone may become compact
bone as spaces fill with bone matrix.
Intramembranous Bones
• Connective tissue on the surface of the bone
forms the periosteum.
• Osteoblasts on the inside of the periosteum
deposit compact bone over spongy bone.
• This process is called intramembranous
ossification.
Endochondral Bones
• Hyaline cartilage forms a model of the
bone during embryonic development.
• Cartilage degenerates, periosteum forms.
• Periosteal blood vessels and osteoblasts
invade the bone forming a primary
ossification center in the diaphysis.
• Secondary ossification centers develop in
the epiphyses.
Endochondral Bones
• Osteoblasts form spongy bone in the space
occupied by cartilage.
• Osteoblasts become osteocytes when bony
matrix surrounds them.
Endochondral Bones
• Osteoblasts beneath the periosteum deposit
compact bone around spongy bone.
• A band of cartilage remains between the
diaphysis and epiphyses as the epiphyseal
disk.
Bone Growth
• Growth of long bones occurs along four
layers of cartilage in the epiphyseal disk.
• First Layer: resting cells that do not grow.
• Second Layer: young mitotic cells.
• Third Layer: older cells that enlarge.
• Fourth Layer: dead cells and calcified
intercellular substances.
Fracture Repair
Fracture Repair
• Blood escapes from damaged blood vessels
and forms a hematoma.
• Spongy bone forms in regions near blood
vessels and fibrocartilage forms farther away.
• A bony callus replaces the fibrocartilage.
• Osteoclasts remove excess bony tissue,
restoring new bone much like the original.
Nutrition and Bone Development
• Vitamin D is necessary to absorb calcium in
the small intestine.
• Vitamin D deficiency leads in rickets in
children and osteomalacia in adults.
• Dehydrocholesterol made in digestive tract
converted to Vit D in the skin by UV rays.
Nutrition and Bone Development
• Vitamin A is necessary for osteoblast and
osteoclast activity.
• Vitamin C is necessary for collagen synthesis.
– Scurvy [skúrvee]
– disease caused by vitamin deficiency: a disease
caused by insufficient vitamin C, the symptoms of
which include spongy gums, loosening of the teeth, and
bleeding into the skin and mucous membranes
Homeostasis of Bone Tissue
•Bone Resorption – action of osteoclasts and parathyroid
hormone
•Bone Deposition – action of osteoblasts and calcitonin
7-10
Hormones and Bone
• Growth Hormone (GH) stimulates
epiphyseal cartilage cell division.
• Deficiency of G H: pituitary dwarfism.
Excess GH: pituitary gigantism in children
and acromegaly in adults.
Hormones and Bone
• Thyroid hormone stimulates cartilage
replacement in the epiphyseal disks.
• Sex steroids promote formation of bone
tissue (ossification) which closes the
epiphyseal disk.
• Estrogen more effective than androgens
Physical Factors Affecting Bone
• Physical stress stimulates bone growth.
• Weight bearing exercise stimulates bone
tissue to thicken and strengthen
(hypertrophy).
• Lack of exercise leads to bone wasting
(atrophy).
Levers are categorized into three
types –
• First class levers (EFL) e.g. a seesaw – the
head on the vertebral column (Figure 11.2a)
• Second-class (FLE) eg. a
wheelbarrow(Figure 11.2b)
• Third-class (FEL) (Figure 11.1b) e.g.
forceps - the elbow joint (Figure 11.2c).
Lever Systems and Leverage
• Muscle acts on rigid rod (bone)
that moves around a
fixed point called a fulcrum
• Resistance is weight of body
part & perhaps an object
• Effort or load is work done
by muscle contraction
• Mechanical advantage
– the muscle whose attachment is farther from the joint will
produce the most force
– the muscle attaching closer to the joint has the greater range
of motion and the faster the speed it can produce
First - Class Lever
• Can produce mechanical
advantage or not depending on
location of effort & resistance
– if effort is further from fulcrum
than resistance, then a strong
resistance can be moved
• Head resting on vertebral column
– weight of face is the resistance
– joint between skull & atlas is
fulcrum
– posterior neck muscles provide
effort
Second - Class Lever
• Similar to a wheelbarrow
• Always produce mechanical
advantage
E
L
– resistance is always closer to
fulcrum than the effort
• Sacrifice of speed for force
• Raising up on your toes
– resistance is body weight
– fulcrum is ball of foot
– effort is contraction of calf
muscles which pull heel up off of
floor
Third - Class Lever
• Most common levers in the body
• Always produce a mechanical
disadvantage
– effort is always closer to fulcrum
than resistance
• Favors speed and range of motion
over force
• Flexor muscles at the elbow
– resistance is weight in hand
– fulcrum is elbow joint
– effort is contraction of biceps brachii
muscle
Blood Cell Formation
• Blood cell formation (hematologists) occurs
in yolk sac in early development.
• Later it occurs in the liver and spleen.
• In the adult red and white blood cells are
formed in the red bone marrow.
Blood Cell Formation
• Red marrow fills the cavity in the diaphysis
of the long bones in infants. In adults it is
replaced with yellow marrow (fat).
• Adult red marrow is found in spongy bone
of the skull, ribs, sternum, vertebrae, pelvis.
Inorganic Salt Storage
• Salts account for 70% of the bone matrix.
• These salts are mostly calcium phosphate
crystals.
• Calcium phosphate ([Ca3(PO4)2] + calcium
hydroxide [Ca(OH)2] called hydroxyapatite
• CaCO3
• Ions – magnesium, fluoride, potassium, &
sulfate
Inorganic Salt Storage
• Parathyroid hormone stimulates osteoclasts
to break down bone when Ca levels are low.
• Calcitonin stimulates osteoblasts to build
bone when Ca levels are high.
• Bone contains Mg, Na, K, and carbonate
ions.