BEN GIO

Plant System

The Shoot System

Vegetative shoots consist of stems and leaves.
"vegetative" - the parts of the plants other than reproductive parts such as the flowers and the fruits.
In biological terms vegetable is a term coined from vegetative parts that are edible.
In kitchen terms you identify orange and apple as fruits while ampalaya and squash are vegetables; but botanically speaking all of these are fruits because they are all reproductive parts of the plants. What are considered vegetables then?

Stems

Support the plant

Xylem

Long thin tubes that transport water

Phloem

Long thin tubes that transport sugars (sap)

Stem Anatomy

Development and structure of primary stem tissues:

Epidermis (outer layer)

A layer of epidermal tissues known as the Epidermis develops at the stem surface Produces a waxy surface coating known as the cuticle, which helps to reduce water loss from the plant surface Helps to protect plants from damage from insects and disease microorganism

TISSUES OF THE STEM

Parenchyma

Beneath the epidermis lies the stem cortex, which is largely composed of ground tissue known as Parenchyma tissues.
thin wall (so that the sunlight can penetrate- mostly much more synthetic function)
This tissue is composed of only one cell type
it has a lot of chloroplasts
Parenchyma cells store starch in plastids (plastid photosynthetic organelles) and thus serve as an organic food reserve
Stem parenchyma also can undergo cell division (meristematic cells or groups of cells that can divide), which aids wound healing when the stem is damaged.

SUMMARY: thin-celled cells so sunlight can penetrate so that CO2 and H20 can diffuse, mostly photosynthetic, has more chloroplast inside, located near the surface.

Collenchyma

composed of flexible
collenchyma cells protection and stability
thicker wall
less synthetic
Provides support

Sclerenchyma

Least synthetic, and forms fibers, fully for protection and structure.
Often aid in defense.

Dermal Tissue

covering like epidermis
Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis.

Vascular Tissue

bundle: channels; two types xylem and phloem

Growth in Stems

Primary Growth (pataas ang growth)

occurs at the apices, or tips, of stems and roots (meristems)

(meristems: small populations of rapidly proliferating cells that produce all the adult organs of a flowering plant. Related to studying cancer or growth of cells, cells that keep on undergoing mitosis.)

Secondary Growth (lateral growth) grows sideways.

The thickening of the stem that occurs in secondary growth is due to the formation of secondary phloem and secondary xylem by the vascular cambium (Cambial layers - are trees that are irregular in shape culture. Tropical trees; messy cambial layer. Temperate; refine cambial layer.).
Plus the action of cork cambium, which forms the tough outermost layer of the stem.
The cells of the secondary xylem contain lignin, which provides hardiness and strength.

Meristematic tissues- are constantly multiplying and are found at the tip
Plants are still plantlets if it is still within the cell because it gets nutrients in the cotyledon.
Cambial layers (cambium) - are trees that are irregular in shape.
Cambial layer or annual growth rings - trees in areas that aren't tropical and are more perfectly shaped circles.
The growth of cells differs in the different seasons:

The rate of wood growth increases in summer and decreases in winter.
This produces a characteristic ring for each year of growth.
Seasonal changes in weather patterns can also affect the growth rate.
Vary in thickness

Annual growth rings: The rate of wood growth increases in summer and decreases in winter, producing a characteristic ring for each year of growth. Seasonal changes in weather patterns can also affect the growth rate. Note how the rings vary in thickness.

Lenticels: on the bark of this cherry tree enable the woody stem to exchange gases with the surrounding atmosphere.

When the plant is green it is still photosynthesizing.
If mo brown mo No green no stomata (pores - called stomata to take in carbon dioxide and release oxygen.
Stomata are tiny, microscopic, and critical for photosynthesis.)

Stem Modification

Rhizome is a modified stem that grows horizontally underground: it has nodes and internodes. Vertical shoots may arise from the buds on the rhizome of some plants, such as ginger and ferns.

Corms are similar to rhizomes, except they are more rounded and fleshy (such as in gladiolus).
Stolons are stems that run almost parallel to the ground, or just below the surface, and can give rise to new plants at the nodes ex. Strawberries

Tubers are modified stems that may store starch, as seen in the potato.

Bulb, which functions as an underground storage unit, is a modification of a stem that has the appearance of enlarged fleshy leaves emerging from the stem or surrounding the base of the stem

Tendrils are slender, twining strands that enable a plant (like the buckwheat vine) to seek support by climbing on other surfaces.

Thorns are modified branches appearing as hard, woody, sharp outgrowths that protect the plant

Bulbils are axillary buds that have become fleshy and rounded due to storage of food.
Cladodes are green branches of limited growth (usually one internode long) which have taken up the functions of photosynthesis.

LEAVES

Contain photosynthetic cells that produce the plant's
food (Glucose)
Stomates-small pores in the leaf's surface
Guard Cells - control the opening and closing of the stomates.
Photosynthesis, Transpiration, Floral Induction, Food Storage, Special uses.

External Parts of a Leaf

Tip/Leaf Apex: This is the tip of the Leaf
Lamina/Blade: This is the blade of the leaf
Margin: This is the outer edging of the leaf. They can be in many different forms i.e. serrated, parted
Midrib: This is the middle vein of the leaf, it connects with the Petiole Lateral Veins: These veins are one of the most important parts of the leaf, they transport the food and water the leaf needs to all it's necessary places
Petiole: This part attaches the leaf to the actual plant stalk.
Stipules: These are found at the base of the plant in pairs attached in between the petiole and the stalk of the plant.

Internal parts of the leaf: (different tissues)

Guard cells: upper and lower margin; are a lot in the lower epidermis than the upper
Upper epidermis: is covered by cuticles para shiny.
Palisade Mesophyll
Spongy Mesophyll: more sparse cay mo absorb ug air
Vein (Vascular Bundle) - made up of phloem and xylem

Leaf Shapes

can be identified the type of tip, margin, apex, shape, petiole carbon dioxide oxygen

Cordate (Heart-shaped)
Linear
Elliptical
Orbicular
Falcate
Reniform (Kidney-Shaped)
Flabellate
Oval
Hastate
Sagittate

Types of Margins:

Entire: having a smooth edge(even edged) with neither teeth or lobes. Without indentations or incisions on margins, smooth.
Serrate (Toothed): having a saw-like margin with small teeth that can vary in size (from very small to medium), in sharpness (from needle-like to soft) and in shape (from rounded to points).
Lobed: having some type of indentation toward the midrib that can vary in profundity and shape (rounded or pointed) and the incisions (sinus) go less than halfway to the midrib. Large, round-toothed, cut 1/8-1/4 distance to midvein
Parted (or cleft): having some type of indentation toward the midrib that can vary in profundity and shape (rounded or pointed) and the incisions (sinus) go more than halfway to the midrib.

Margins can also be a combination of toothed, lobed, parted and smooth

Reproductive Plant Parts

Complete flower structure

Imperfect (pistillate) flower structure

Plants with imperfect flowers are further classified as monoecious or dioecious.

Monoecious plants have separate male and female flowers on the same plant (e.g., corn and pecan). Some monoecious plants bear only male flowers at the beginning of the growing season, but later develop both sexes (e.g., cucumbers and squash).
Dioecious species have separate male and female plants.

Fruit

Structure

Fruit consists of fertilized, mature ovules (seeds) plus the ovary wall, which may be fleshy, as in an apple, or dry and hard, as in an acorn In some fruits, the seeds are enclosed within the ovary

(e.g., apples, peaches, oranges, squash and cucumbers).

In others, seeds are situated on the outside of fruit tissue (eg, com and strawberries).

The Root Systems

Functions of Roots:

Provide support
Absorb water
Osmosis occurs at the root tip.
May contain sugars that help the plant get energy

Homeostasis in Plants

Like animals, plants also "breathe," though the exchange is the reverse of what we do. Plants take in carbon dioxide and release oxygen. Did you know they also regulate how much they take in and let out?
Leaves have stomata, holes on the underside, that expand and contract to get just the right combination. That's homeostasis. Leaves are machines for maintaining homeostasis. In addition to the process of photosynthesis described above, those same stomata take in and excrete nutrients, including salt and many others, based on whether the plant needs more or less.
Stomata are a triple threat. They regulate photosynthesis and plant nutrition, but they also maintain a plant at the optimum water level. When stomata open wide, they dry the plant out. When they close, they help retain water.
Plants go to great lengths to maintain the proper temperature too. Being less mobile than the average animal, plants have to get creative. Sunflowers, for example, got their name for a reason: they're heliotropes, following the sun across the sky to maximize photosynthesis. Plants also undergo gravitropism, using gravity to guide their growth. Roots have evolved to go towards gravitational pull, while shoots shoot up against it.
Plants have beneficial bacteria in their system just like animals. There's a whole category of microorganisms called PGPR, or "plant-growth promoting rhizobacteria. The bacteria occurs in soil and likes to hang out in roots. In fact, they like it so much, they pay rent: PGPR fend off other microbes that cause disease and help plants use minerals and make important hormones.
Water Homeostasis in Plants:

Stomata Open -

When there is sufficient water |

Allows CO2 IN
Allows H2O OUT

Stomata Closed -

Under dry conditions

Keeps H2O in, but doesn't get any CO2

Movement of Food and Water

Water:

Transport moves water from roots through the Xylem To all parts of the plant.
Mainly Leaves.

Food:

Transport moves sugar From the Leaves through the Phloem To all parts of the plant Mainly Roots(storage).

Water Movement

Transpiration - Water moves into roots by diffusion (osmosis). Water evaporates from the stomata creating a suction Water flows from the roots to the leaves to replace the lost water
Capillary Action - movement of water into small spaces Root Pressure - diffusion of water into roots creates a pressure

Sugar Transport

Pressure flow model

Transport moves sugar from the leaves through the stem to all parts of the plant, mainly the roots (storage).

Regulation of Plant Growth

Photoperiodism- the response a plant has to the light and dark hours
Hormones - chemical messengers that regulate plant function
Auxins - hormones that stimulate plant growth. Located at root tips and stems. Tropism- Plant growth towards a stimulus Phototropism - growth towards sun(leaves)
Geotropism - growth towards earth(roots)

Plant Nutrition

Photosynthesis - Capturing sunlight to make food (glucose)

Photosynthesis is the source of most of the oxygen in the air.
Occurs within the Chloroplasts which contains Chlorophyll (green pigment)

It absorbs light energy from the sun to make glucose Chlorophyll absorbs red & blue and reflects Green light.

INTEGUMENTARY SYSTEM

FUNCTIONS

covering and protection
secretions of substances
excretion of metabolic wastes
sensation
respiration
regulation of temperature
storage of reserved food
nourishment for the young
Locomotion

THE SKIN

considered as the true integument covering the surface of the body
largest organ of the vertebrate body, 15 to 16% of the total body weight in adult human
covers an area of about 17.5 square feet for an average woman and about 20.0 square feet for an average man
about 1 to 2 mm thick; only 0.5 mm on the eyelids and up to 6 mm on palms or soles
about 40 kg (88 lb) of dead skin is shed in a lifetime
one sq cm of human skin contains 200 nerve endings, 10 hairs and muscles, 100 sweat glands, 15 oil glands, 3 blood vessels, 12 heat receptors, 2 cold receptors, and 25 pressure-sensing receptors

Layers of the Skin

Epidermis

made up of stratified squamous layer of epithelial tissue
10 to 30 cells thick, about as thick as this page

Layers of epidermis

stratum corneum outermost layer; composed of dead cells; keratinized;
stratum lucidum translucent layer; composed of flat dead and non-nucleated cells
stratum granulosum composed of keratohyalin granules
stratum spinosum prickle cell layer; composed of Langerhans cells
stratum germinativum (basale) inner layer; composed of actively dividing cells

Epidermal Cells

Keratinocytes - 90% of epidermal cells; produce keratin
melanocytes - 8% of epidermal cells; produce melanin
Langerhans cells - capable of trapping antigen in the skin
Merkel cells - make, contact with the ending of a sensory neuron

Dermis

made up of fibrous connective tissue containing collagen and elastic fibers
also contains muscle fibers, glands, pigment cells, blood vessels, and sensory nerves

15 to 40 times thicker than the epidermis

provides structural support for the epidermis and as matrix for many nerve endings, muscles, and specialized cells in the skin

Regions of the dermis

1. papillary region consists of areolar connective tissue; forms the dermal papillae; some contains tactile receptors called Meissner's corpuscles

2. reticular region consists of dense, irregular connective tissue; attached to underlying organs

Sensory receptors in the dermis

Meissner's corpuscles - for light touch
Pacinian corpuscles - for deep pressure
Naked nerve endings - associated with hair follicle for pain and light touch
Corpuscles of Ruffini - for heat
End bulb of Krause - for cold

Subcutaneous Layer

composed of fat-rich cells
acts as shock absorbers
provides insulation to conserve body heat

Skin Derivatives

Cutaneous or Dermal Glands

- glands originating from the epidermal cells that have invaginated into the dermis

Types as to methods of secretion

merocrine glands "true glands"; not destroyed during secretion; most sweat glands
apocrine glands part of the cell is destroyed that go with the secretion; mammary gland and some sweat glands
holocrine glands the entire cell goes with the secretion but a new cell is produced to replace it; sebaceous or oil gland

Types as to secretory products

serous glands - watery substance; sweat glands
sebaceous glands oily substance called sebum
mucous glands - substance with mucin

Keratinized derivatives

non-living structures found on the outer layer of the epidermis
include the hair of mammals, feathers of birds, nails or claws, beak, scales of reptiles, scutes of turtles, and true horns (hollow)

Dermal derivatives

non-living structures found on the outer layer of the epidermis
include the false horns (solid), plates of turtles, and scales of fishes

COMMON SKIN DISORDERS

Acne, eruptive skin disease. It is primarily a disorder of the sebaceous follicles of the skin and appears most often on the face, neck, and back. The natural secretion, or sebum, of the follicles accumulates and mixes with dust and dirt. The follicles and surrounding tissue become inflamed and blackheads appear. If the follicle opening completely closes, the accumulated sebum is degraded by bacteria and forms a cyst.
Eczema, an inflammatory, chronic, non-contagious disease of the skin caused by allergy and hypersensitivity. The term is loosely used to include many skin conditions more properly included under dermatitis. Eczema is characterized by a number of cutaneous lesions, such as macules, papules, pustules, vesicles, scales, and crusts. Macules are non-elevated skin spots. Papules are hard, circular, and elevated. Pustules are popular-like lesions that contain pus, and vesicles are small skin blisters that contain fluid. Eczematous lesions are usually accompanied by an exudation of serous fluid and by intense itching. One-third to one-half of all cutaneous conditions is eczematous.

Skeletal System

Functions

Support the body
Attachment of muscles
Protection of internal organs
Acts as levers for movement
Gives stability, framework, and shape to the body
Production of blood cells (in mammals)

Types of Skeleton

As to Formation

Membrane or Dermal Bone – Formed by direct ossification in connective tissue without an intervening cartilage stage
Endochondral or Cartilage Bone – Formed by replacement of pre-existing cartilage

As to Kinds of Bone Tissue

Spongy Bone Tissue
- Located at the ends and interiors of long bones
- Also called bone marrow
- Composed of an open lattice of bone
- RBCs are produced within this lattice framework
Compact Bone Tissue
- Surrounds the spongy bone tissue
- Also found at the core of bones
- Gives strength to withstand mechanical stress

As to Location

Exoskeleton or Dermal Skeleton
- Built up outside the body
- Muscles are attached to the inner surface
- Limits the size of the animal
- Formed from a secretion called chitin, hardened by calcium salts
- Characteristic of arthropods
Endoskeleton
- Built up inside the body, surrounded by soft tissue
- Muscles are attached to the outer surface
- Characteristic of vertebrates
- Divided into axial and appendicular skeletons

Axial Skeleton

Forms the main axis of the body
Composed of the notochord, vertebral column, ribs, sternum, and skull

Notochord

Primitive axial skeleton, replaced by the vertebral column
Unsegmented, composed of dense fibrous connective tissue
First skeletal element to appear in the embryo of chordates

Vertebral Column

Main axial support of vertebrates (backbone)
Composed of segmentally arranged vertebrae from the base of the skull to the tip of the tail
Protects the spinal cord, provides rigidity to the body, and direct/indirect attachment of the appendicular skeleton
Human Vertebrae (26 total)
- 7 cervical (1st is atlas, 2nd is axis)
- 12 thoracic
- 5 lumbar
- 1 sacral (five fused to form sacrum)
- 1 caudal vertebrae (three to five fused to form coccyx)

Regions of the Vertebral Column

Fishes: Trunk and tail
Frogs: Four regions, no neck
Salamanders, Reptiles, Birds, Mammals: Five regions – cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), caudal (tail)

Ribs

Series of cartilaginous or bony structures attached to the vertebrae
Stout, arched structures forming the thoracic cage
Human ribs (12 pairs)
- 1st seven pairs: Vertebrosternal or true ribs
- Next three pairs: False ribs
- Last two pairs: Floating ribs

Types of Ribs

True Ribs – Directly connected to the sternum
False Ribs – Distal cartilaginous ends unite with the costal cartilages of the last true ribs
Floating Ribs – Distal cartilaginous ends terminate freely

Sternum

Commonly called the breastbone
Elongated structure in the mid-ventral region of the anterior trunk
Parts of the human sternum:
- Manubrium – Upper part
- Gladiolus – Middle and largest part
- Xiphoid Process – Lowest portion, no ribs attached

Skull

Framework of the head, most complex part of the endoskeleton
Cartilaginous during embryonic stage

Origin of the Skull

Chondrocranium – Cartilage; forms the base of the skull and sense capsules; later replaced by bone
Dermatocranium – Membrane bones; forms the roof over the chondrocranium
Splanchnocranium – Derived from visceral skeleton; cartilaginous, covered by membrane bones

Parts of the Skull

Cranium – Brain case
Three pairs of sense capsules – For smell, sight, and hearing
Visceral Skeleton –
- Lower vertebrates: Provides jaws, tongue support (hyoid apparatus), and gill region support
- Higher vertebrates: Hyoid apparatus, ear ossicles (incus, malleus, stapes) for sound conduction, laryngeal and tracheal cartilages

Appendicular Skeleton

Consists of anterior pectoral appendages and girdle and posterior pelvic appendages and girdle
Fishes: Appendages are fins
Tetrapods: Appendages are limbs

Composition of the Appendicular Skeleton

Pectoral Girdle

Scapula – Shoulder blade
Coracoid
Clavicle – Collarbone

Forelimbs

Humerus – Upper arm
Radius and Ulna – Forearm
Carpals – Wrists
Metacarpals – Palm
Phalanges – Fingers

Pelvic Girdle (Hip Bones)

Ilium
Ischium
Pubis

Hindlimbs

Femur – Thigh
Tibia and Fibula – Shank
Patella – Knee cap
Tarsals – Ankle
Metatarsals – Sole
Phalanges – Toes

Distribution of Bones in Human Adults

Total: 206 bones
Infants have more bones due to numerous joints

Joints

Articulations between cartilages or bones
Study of joints: Syndesmology

Types of Joints

As to Amount of Movement & Structural Composition

Synarthroses – Immovable joints (e.g., skull sutures)
Amphiarthroses – Slightly movable joints
Diarthroses – Freely movable joints (most common)

Types of Diarthroses

Gliding Joint – Wrists, ankles, vertebrae
Hinge Joint – Knee, elbow, phalanges
Condyloid Joint – Wrist joint
Saddle Joint – Thumb
Pivot Joint – Atlas and axis, radius and ulna
Ball-and-Socket Joint – Shoulder and hip

Gait

Manner of walking

Types of Gait

Plantigrade – Whole foot touches the ground (e.g., humans, bears)
Digitigrade – Digits with pads touch the ground (e.g., cats)
Unguligrade – Hooves touch the ground (e.g., cows, horses)

Common Disorders

Osteoporosis – Decreased bone mass, increased fracture risk
Scoliosis – Lateral curvature of the spine

MUSCULAR SYSTEM

FUNCTIONS

Voluntary Functions

Maintenance of posture
Accomplishment of various movements

Involuntary Functions

Propulsion of substances through the body passages
Expulsion of stored substances
Regulation of size openings
Regulation of the diameter of tubes

TYPES OF MUSCLES

Skeletal - (striated, voluntary)
Visceral - (smooth, involuntary)
Cardiac - (striated, involuntary)

AS TO STRUCTURE

Striated Voluntary Muscle Tissue

Also called skeletal muscle
Composed of long, cylindrical cells (filamentous)
Contains thin and transparent sarcolemma
Sarcoplasm contains parallel rows of myofibrils with alternating light (I-band) and dark bands (A-band) forming striations
Multinucleated
Found attached to the skeleton by a tendon, responsible for the voluntary (controlled by the will) movement of the body

Striated Involuntary Muscle Tissue

Also called cardiac muscle
Composed of linear, branching bundles of fibers joined end to end by the intercalated disc
With elongated nucleus centrally located between diverging cells
Found in the walls of the heart, bringing about the involuntary contraction of the organ

Smooth Involuntary Muscle Tissue

Also called visceral muscle
Composed of elongated cells with tapered ends (fusiform)
Contains homogenous or clear sarcoplasm
Centrally located nucleus
Found in internal organs which bring about involuntary movement in these organs

AS TO ACTION

Agonist or Prime Mover - Principal mover for specific action; deltoid muscle in abduction of arm
Antagonist - For opposite movement; latissimus dorsi and pectoralis for deltoid muscle
Synergist - Helps to stabilize the movement of one joint and inhibit undesirable movements
Fixator - Fixes the position of the limb when the movement is occurring; biceps and triceps, they hold the shoulder and elbow in position

AS TO SPECIFIC FUNCTION

Flexors - Bend a limb or one part of a limb against another
Extensors - Straighten a limb or one of its component parts
Adductors - Draw a part toward a median line or toward a neighboring part or limb
Abductors - Draw a part away from a median line or from a neighboring part or limb
Pronators - Turn or rotate a part downward on its axis, palm of the hand
Supinators - Turn or rotate a part forward and upward on its axis
Elevators or Levators - Raise or lift a part as when the lower jaw in closing the mouth
Depressors - Lower or depress a part as when the lower jaw in opening the mouth
Constrictors - Draw parts together or compress a space such as the pharynx and the abdomen
Dilators - Widen an opening or a space
Sphincters - Constrictors surrounding an opening such as the mouth, pylorus, and anus

STRUCTURE OF SKELETAL MUSCLE

The entire muscle is surrounded by an external connective tissue wrapping called the epimysium
Skeletal muscle is made up of fascicles, which are bundles of individual muscle cells called muscle fibers
Each fascicle is surrounded by a connective tissue layer called the perimysium
Within each fascicle, the third connective tissue layer, the endomysium, separates and electrically insulates the muscle fibers from each other
All three connective tissue layers bind the muscle cells together providing strength and support to the entire muscle
Each muscle fiber is subdivided by the sarcoplasmic reticulum into smaller cylinders called myofibrils
The myofibril is composed of sarcomeres, attached end to end
Within each sarcomere are alternating thin and thick myofilaments of actin and myosin proteins respectively
The arrangement of thin and thick myofilaments forms light (I band) and dark (A band) alternating bands or striations along the myofibrils

MUSCLE PROTEINS

Myosin - Composes the thick myofilaments
Actin - Composes the thin myofilaments
Troponin - Subcomponent of thin myofilaments
Tropomyosin - Subcomponent of thin myofilaments
Myoglobin - Muscle hemoglobin for transport of oxygen

MUSCLE METABOLISM

The energy necessary for muscle contraction is provided by ATP
ATP must be synthesized in muscle cells to replace the ATP used for muscle contraction
ATP is synthesized by hydrolysis of creatine phosphate, glycolysis, Krebs cycle, and oxidative phosphorylation
There are 2 types of muscle fibers based on different methods of synthesizing ATP:
- White muscle fibers - Mainly use glycolysis; these fibers are quick and powerful but fatigue rapidly
- Red muscle fibers - Mainly use Krebs cycle; these fibers are fatigue-resistant and have high endurance

MOTOR UNIT

A motor unit is composed of a motor neuron and all of the muscle cells it stimulates
The number of muscle cells within a motor unit determines the degree of movement when that motor unit is stimulated
- Small motor unit - Contains few muscle cells, found where precise movements are needed
- Large motor unit - Contains a large number of muscle cells, found where gross movements are needed

COMPOSITION AND STRUCTURE OF MYOFILAMENTS

Thick Filament (Myosin)

Composed of a tail with 2 heads
The head (cross bridge) has the ability to move back and forth, providing power stroke for muscle contraction
The cross bridge has 2 binding sites:
- ATP binding site
- Actin binding site
The tail allows vertical movement so that the cross bridge can bind to actin

Thin Filament

Composed of actin filaments twisted into a double helical chain
Each actin filament has a specific binding site to which the myosin cross bridge binds
Tropomyosin entwines around the actin
In a resting muscle, the position of tropomyosin covers the binding sites on the actin filaments, preventing myosin cross bridge binding
Troponin is attached and spaced periodically along the tropomyosin strand
Calcium ions are released from the terminal cisternae and bind to troponin, causing a change in the troponin-tropomyosin complex, exposing the binding sites

STIMULATION FOR CONTRACTION

Action potential arrives at the axon terminal, opening Ca²⁺ channels
Ca²⁺ enters, pushing the synaptic vesicle to the membrane
Acetylcholine is released into the synaptic cleft and binds to receptor sites
Influx of Na⁺ and efflux of K⁺ causes local depolarization
Depolarization initiates action potential along the sarcolemma
Action potential triggers Ca²⁺ release from terminal cisternae, triggering contraction

CONTRACTION OF MYOFILAMENTS (Sliding Filament Theory)

Influx of Ca²⁺ exposes binding sites on actin
Binding of myosin to actin (ATP used)
Powerstroke of myosin slides filaments
ATP binds to cross bridge, disconnecting it
Hydrolysis of ATP re-energizes cross bridge
Efflux of Ca²⁺ covers actin binding sites

COMMON DISORDERS ASSOCIATED WITH MUSCLES

Gout - Faulty metabolism of uric acid
Arthritis - Inflammation of joints (Osteoarthritis, Rheumatoid Arthritis)

DIGESTIVE SYSTEM

FUNCTIONS

Ingestion of food
Breaking down of complex substances (food) into simple forms (nutrients)
Absorption of digested food
Egestion or excretion of undigested food

TYPES OF DIGESTION

As to Action

Mechanical digestion – food is converted into small pieces by physical means such as mastication by the teeth
Chemical digestion – food is converted into simpler forms by the action of enzymes

As to Location

Intracellular digestion – inside the cell particularly in the lysosomes, characteristic of unicellular organisms
Intercellular or extracellular digestion – inside the digestive tube outside the cell

COMPOSITION OF EXTRACELLULAR DIGESTION

Digestive Tube

Also called the alimentary canal
Over 30 ft long in humans, beginning in the mouth and ending in the anus

Digestive Glands

Organs that secrete juices containing enzymes for digestion of food
Examples: salivary glands, mucous glands, gastric gland, pancreas, intestinal gland, and liver

Accessory Parts

Includes structures that help in digestion
Example: tongue and teeth

PARTS OF DIGESTIVE TUBE

Mouth

Anterior opening
Guarded by upper and lower lips
Entrance of food

Oral Cavity or Buccal Cavity

Cavity inside/behind the mouth
Site of mastication and lubrication of food
Contains accessory structures:
1. Oral glands – not located in the oral cavity but their ducts open into it
  - Secretes mucus for lubrication of food
  - Saliva contains enzymes used in digestion
2. Tongue – muscular organ
  - Used for catching prey in frogs
  - Acts as a thermoreceptor and chemoreceptor in snakes
  - Used for tasting, manipulation of food, and aid in swallowing in humans
3. Teeth – found in the anterior and lateral sides of the oral cavity
  - Used for offense and defense
  - Used for mastication of food

External Parts of Tooth

a. Crown – exposed part
b. Root – hidden part
c. Neck – between the crown and the root

Internal Parts of Tooth

a. Enamel – outermost and hardest part
b. Dentine – slightly elastic, softer part beneath the enamel
c. Pulp cavity – inner part, soft tissue enclosed by the dentine; contains blood vessels and nerves
d. Cementum – thin layer of material covering the root

Types as to Structure and Function

a. Incisors – sharp, chisel-like teeth at the front of the mouth, for cutting food
b. Canines – round, pointed teeth at the corners of the mouth, for tearing and gripping food
c. Premolars and molars – square teeth with small cusps at the back of the mouth, for grinding food

Types as to Appearance

a. Primary teeth – also called milk teeth

Appear 6 to 24 months after birth
Gradually fall out and are replaced by permanent teeth
Consist of 20 teeth (4 incisors, 2 canines, 4 molars)
b. Permanent teeth – appear from age 6 and completed by age 13
"Wisdom teeth" appear as late as 25
Consist of 32 teeth (4 incisors, 2 canines, 5 molars)

Pharynx

Narrow space behind the oral cavity
Common passageway for food and air

Esophagus

Narrow muscular organ between the pharynx and stomach
Peristalsis movement

Stomach

Largest and highly muscular part of the digestive tube
Suspended by the mesogaster
Maximum capacity of 2.5 pints
Food stays for about 3 to 5 hours
Churning movement
Internally lined with numerous folds or rugae where gastric glands are located

Parts/Divisions of the Stomach

Cardiac sphincter – anterior end; prevents backward movement of food to the esophagus
Fundus – most expanded part of the stomach
Pyloric sphincter – posterior end; regulates movement of food to the small intestine

Small Intestine

Longest and most coiled part of the digestive tube
Site of final digestion and absorption
Suspended by the mesenterium
About 22 ft long; food stays around 4.5 hours
Segmenting movement
Internally lined with numerous folds or villi that increase surface area for absorption

Parts/Divisions of the Small Intestine

Duodenum – anterior end; uncoiled, around 12 inches long
Jejunum – middle division; coiled
Ileum – posterior end

Large Intestine

Posterior part of the digestive tube
Joined to the small intestine through the ileocolic junction (vermiform appendix)
Suspended by the mesocolon or mesorectum
Food stays for about 5 to 25 hours or more
Absorbs water

Parts/Divisions of the Large Intestine

Caecum – anterior portion; appendix is located
Colon – middle portion; divided into ascending colon, transverse colon, descending colon, and sigmoid colon
Rectum – posterior portion; temporary storage of undigested food

Anus

Posterior opening of the digestive tube
Exit of fecal matter; regulated by the anal sphincter
In some vertebrates, the posterior opening is the cloaca, a common passageway for reproductive cells and feces