Human Anatomy I:Tissues, Skin & Bones

Some Basic Ideas Anatomy describes the physical parts of an

organism Physiology describes the way in which

those parts work, alone and in combination Most organisms are organized into

different levels: Cells Tissues: groups of cells performing some

specific function Organs: groups of tissues performing some

specific function Organ systems: groups of organs performing

some specific function

Tissue Types There are 4 main

kinds of tissues Epithelial Tissue Connective Tissue Muscle Tissue Nerve Tissue Most organs are a

combination of two or more tissues

Epithelial Tissue Serves as covering or lining of various body parts Involved in both absorption of material and

secretion of material Cells can vary in shape:

Squamous cells are flat; found in areas where diffusion important

Cuboidal cells are cubes; involved in secretion and absorption

Columnar cells are rectangular: also used for secretion and absorption

Tissue can vary in # of layers: Simple epithelium has one layer Stratified epithelium has 2 or more; can be

different cell types

Clockwise from upper left: simple columnar; simple cuboidal; stratified squamous

Connective Tissues

Perform a variety of functions All consist of two components:

Living cells, scattered in a… Non-living matrix secreted by

these cells Some examples include:

Bones Cartilage Adipose (fatty) tissue Blood Ligaments tendons

Major Organ

Systems

Integumentary System Or, more commonly, skin! Major functions include:

A barrier to injury or invasion by other organisms

A (very large) sensory organ Production of body covering (hair, scales,

feathers) Production of various substances (toxins,

pheromones, lubricants, etc.) Body cooling (via sweat) Assistance with respiration

General Anatomy of the Skin I Outermost layer is the epidermis

Living epithelial cells towards interior Outer layer of dead cells, many filled

with keratin (helps prevent water loss)

General Anatomy of the Skin II Middle layer is the

dermis Contains primarily

connective tissue, plus nerves, blood vessels, muscles, sensory organs

Hairs and glands appear to come from this region, but actually are infoldings of the epidermis

General Anatomy of the Skin III Inner layer is the hypodermis, or subcutaneous

layer Mostly a layer of adipose tissue, which helps…

Cushion underlying organs In heat retention

Also contains some nerves and blood vessels

2 Primary Skin Glands in Humans

Sweat Glands, with two types: Eccrine sweat glands occur over most of

body Release a clear fluid, mostly water with dissolved

salts

Apocrine sweat glands are found mostly in groin, armpits, face Release more viscous and odor-causing fluid

Sebaceous Glands Release a thicker, oily/waxy fluid called

sebum Helps lubricate hair follicles

Human skin also possesses a number of different kinds of sensory receptors (for temperature, pressure or touch, pain)

Skeletal System Major functions include:

Protection for internal organs Attachment points for muscles

Some animals possess a hydrostatic skeleton Body is a fluid-filled “bag” under

pressure which animal can push against Others have an external skeleton, or

exoskeleton Still others possess an internal

skeleton

Above are some hydrostatic skeletons, in a roundworm and an earthworm. To the right is a shed exoskeleton of a cicada.

Anatomy of the Human Skeleton

The axial skeleton consists of bones along the midline of the body Includes skull, spinal column, ribcage,

sternum The appendicular skeleton is

everything else Includes arm bones, leg bones, pelvic

girdle, pectoral (shoulder) girdle

Axial skeleton

Appendicular skeleton

3 Components of Skeleton Bones: the hardest

part of the skeleton Cartilage: more

flexible than bone Ligaments: a type

of connective tissue linking two bones

NOTE: tendons link muscles to bones, but we’ll look at these with muscles

Bone Structure Bones may be long, short, flat, or

irregular in shape Most bones have a dense region of

compact bone, and a less dense region of spongy (or cancellous) bone

Within the spongy bone of long and flat bones is red marrow Involved in production of red blood cells

Within the shaft region of long bones is yellow marrow Mostly fat storage Can be converted to red marrow in

emergencies

Long bones above, flat bones below

The Inside of Bones The living cells in bones are called osteocytes

Osteocytes are found within spaces called lacunae Osteocytes produce bone, which is the non-living matrix part

Osteocytes are arranged (at least in compact bone) in groups called osteons, or a Haversian system

In the middle of each osteon is a canal containing blood vessels to nourish the osteocytes

Joints Joints occur where

two bones come into contact and can move relative to each other

At the end of each bone is a layer of cartilage

Ligaments link bones Fluid usually fills

space between bones to reduce friction and wear