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Factors that play a role in postmortem decomposition
- Temperature
- Clothing (cotten/linen vs. polyester)
- Insect Activity
- Trauma
- Surface/Burial/Water
- Predators
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Cooling of the body
- Deep organs cool slower
- Gross errors can occur (especially in countries like Saudi Arabi where ambient temperature exceeds 40C; body may "warm up")
- On average, exposed skin feels warm to touch 6-8 hrs
- For forensic anthropologists, no thermometer is going to help
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postmortem hypostasis
- Lividity (settling of RBCs with discoloration)
- Often called livor mortis
- Supine position - seen on back, buttocks, thighs, and calves
- Pressure from clothiing (like a strap) or lying on hard surface
- Areas are pale - NOT trauma
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taphonomy
- transition of a body from the time of death through decomposition, destruction, transport, or burial to fossilization
- Fossilization is the exception, not the rule
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5 Stages of Decay
- Fresh: starts at death; ends with beginning of bloat
- Putrefaction/Bloat
- Decay
- Dry: tough fibrous materials survive up to 6 mos (tendons, ligaments, uterus & prostate)
- Skeletal
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PMI
- Postmortem Interval
- Time since death
- Different "causes" of death but death occurs after irreversible cardiac arrest
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irreversible cardiac arrest
- cardiorespiratory function fails
- collapse of blood pressure
- supply of oxygenated blood to brain gone
- loss of cerebral function
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Forces that promote decay: insect activity
- Flies don't lay eggs in rain
- Generally insects (typically secondary screw worms) lay eggs within minutes (at temperatures above 50F)
- Eggs hatch within 8-18hrs (from time insects have access to the remains)
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Decay in Louisiana
- Within 24 hrs, a body can be swollen beyond recognition
- Within 2 weeks (in extreme cases), body skeletalized
- Within 6-8 mos (rule of thumb), tendon and ligamentous attachments still in place
- By one year after death, typically clean bone
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Mummification
- Occurs occasionally
- Dessication - drying out of skin and organs or just outer skin
- Desert-like conditions (Egypt, S. America - Andes)
- More often seen in newborn infants (virtually "sterile" emerging from uterus and may "dry up" before bacterial action occurs)
- Cool dry conditions (hay lofts, barns) - partial mummification
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Insects of Special Interest
- Non-native to LA
- Hairy Maggot Blowfly: cannibalistic; will eat other insect larva
- Fire Ants: eat larva and eggs
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Cadaver dogs
- Potential use
- Must be careful
- Worst part: trainers/owners
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Putrefaction/Bloat
- Usual course of decomposition
- Moist degeneration leading to liquefaction of soft tissues
- In temperate climates, usually seen on 3rd or 4th day
- In tropics, subtropics (LA), or summer in temperate climates, may start within hours after death
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Putrefaction/ Bloat breakdown
- abdominal wall where gut bacteria proliferate and decompose hemoglobin into green compounds - stains skin
- gas forms
- body swells
- progressive bloating of face, abdomen, breasts, and genitals
- superficial veins become outlined in red or green (marbled appearance)
- skin blisters as epidermis peels off
- tongue & eyes protrude due to internal gas pressure
- bloody fluid squeezed up from decomposing lungs
- air passages leak or "purge" out of mouth & nostrils
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Insect Life Cycle
- Adult
- Eggs
- Larva (maggots) - go through instar (stages of growth)
- Pupa
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rigor mortis
- most dead bodies become stiff
- occurs at variable times after death
- rigor passes, body becomes limp again
- only practical use - to estimate time of death
- absent or hardly detectable in infants & the old and feeble
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Why does rigor mortis appear more quickly in persons who die during or soon after physical exertion or exhaustion?
- Glycogen (energy source) is depleted at this time
- speeds up the physiochemical process of rigor
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How to find a buried body
- Informant/Accident
- Probing: use of metal rod to determine outline/area of burial pit
- Depression: evidence that soil has been overturned
- Vegetation: organic matter from decomposition provides nutrients for vegetation ("grass is greener over the septic tank")
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Field Recovery: Unit Set-up
- 10' square: use feet/inches when working with law enforcement; other scenaries use metric
- Back Hoe: depth of burial may indicate premeditation
- Shovel Skimming
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adipocere
- hydrolysis of adipose tissue
- decomposition of fatty tissue
- "grave wax"
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True or False: All bone is ivory colored
- Bone is porous and will take on the color of the environment around it after it has been there for a while (i.e. red Native American bones)
- All bone is ORIGINALLY ivory colored
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general rule of body dumping
As a general rule, killers do not take bodies further than 1/4 mile from the nearest road access by vehicle
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Field Recovery: Equipment Needed
- Portable Field Kit
- Metal Detector
- Shovels
- GPS
- Camera
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Field Kit Materials
- Multiple tape measures (10m and 100m)
- Wooden stakes, string
- Line level, plumb bob
- Flags
- Trowels
- Perino picks - piece of cane stripped and rounded off (soft touch; will not damage bone)
- Brushes
- Dust pans, whisk brooms
- Bags - paper, plastic (assorted sizes)
- Body bag
- Pencils and Sharpies
- Graph paper
- Eye protection, Gloves, Insect Repellent
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Partially Decomposed Remains
- Munsell chart - soil chart
- Generally can find original position of body because of a stain left by body decomposition
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Scene Presevation
- Use caution tape
- Make a standard path and stick to it
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Plan view
map as though you were looking at the scene from above
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Field Recovery Map
- North arrow
- Anchor the map (link to a datum point)
- Scale
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Post-Cranial Skeletal Positional Terms
- Proximal: the part of the bone closest to the skull
- Distal: the part of the bone furthest from the skull
- Medial: part of bone closest to the midline of the body
- Lateral: part of bone furthest from the midline of the body
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Cortical Bone
dense, outer layer of bone
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Trabecular (Spongy) Bone
- Made of same material as cortical, but loosely packaged/organized
- Seen especially on the ends of long bones
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Periosteum
- thin organic sheath covering all bone (especially long bone) but sub-chondral
- Osteogenic: bone cell forming
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Chondral
all bone with periosteum
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Subchondral
- bone at joints (knee, shoulder, hip, etc.) nourished by synovial fluid
- Cartilagenous joints to NOT have periosteum
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Synovial fluid
- Lubricant which helps to cushion (along with cartilage) and absorb pressures placed on knee, shoulder, hip, etc.
- Helps to nourish non-vascular cartilage
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Foramen magnum
hole where spinal cord enters brain
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Layers of teeth
- Enamel
- Dentin
- Pulp - organic material (nerve endings) and DNA
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Baby Dental Formula
- 2102/2102
- 2 incisors, 1 canine/cuspid, 1 premolars, 2 baby molars
- 20 teeth
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Adult Dental Formula
- 2123/2123
- 2 incisors, 1 canine/cuspid, 2 premolars/bicuspids, 3 molars
- 32 teeth
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Central & lateral incisors function
grabbing and holding
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Canines function
nipping & holding
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Premolars function
grinding & chewing
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Molars function
grinding and chewing
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deciduous teeth
- Baby teeth
- 20
- Born with tooth buds
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Types of Sutures
- Coronal suture: separates the front of the skull from the back ("crown")
- Sagittal suture: separates the skull from left to right
- Lambdoidal suture: runs along the back of the skull
- Squamosal suture: NOT interlocking; two bones rest against one another; temporal bone & parietal bone (like a bevel mirror); WEAK
- Basilar suture: completely fuses around the age of 18
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Cranial deformation
- Skulls of children are more malleable than those of adults
- Deforming the shape of a skull
- Reflects social status
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4 factors that lead to variation in human skeleton
- Ontogeny: growth
- Sexual dimorphism: differences in the sizes between the sexes
- Geographic location: where the person grew up
- Normal variation between or among individuals
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Hydroxyapatite
- Mineral in bone
- Gives bone its toughness
- Makes the bone dynamic
- If you put bone in a certain type of acid, it dissovles the hydroxyapatite, makes the bone rubbery
- If you heat bone and dry it out, it becomes brittle (bone has been used as fuel)
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Collagen
- 90% of bone
- Organic matter
- Interwoven with many minerals to make it strong
- Bones must deal with compression, tension, torsion
- Bones are flexible in some ways to a certain point
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What is bone made of?
- Both minerals and organic matter
- 90% organic matter is a protein called collagen
- Minerals - hydroxyapatite
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Osteoblasts
- Form bone matrix
- Blast - build
- Constantly at work
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Osteocytes
- Maintain bone tissue
- Participate in mineralization
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Osteoclasts
- Destroy bone tissue and calcified cartilage through resorption
- Clastic activity is destructive activity
- Histologically, osteoclasts are always associated with bone resorption at an existing bone surface
- In a single day, an osteoclast can destroy what it took 100 osteoblasts to form in the same peroid
- Most diseases result in osteoclastic activity (venereal syphilis starts in long bone, affects skull)
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What is responsible for the gross appearance of bone?
Osteoclasts and osteoblasts
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3 Types of Embryonic Tissue
- Ectoderm: forms tooth enamel
- Mesoderm: forms dentin, bone, cartilage
- Endoderm: forms body organs, etc.
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Wolff's Law of Bone Transformation
- Bone will restructure itself in order to optimally resist stress
- Established by Dr. Wolff in 1862
- Hormonal activity will instruct to build or destroy bones as necessary
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Death Investigation
- Determines cause and manner of death
- Cause: massive hemorrhage; car crush; blunt force trauma
- Manner: accident, suicide, homicide, natural causes, unknown
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Forensic Anthropologists
- Main job - indentification of individual
- Secondary job - what happened to individual
No putative ID - estimate PMI (postmortem interval), perform facial reconstruction, enter into databases
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Antemortem injury
- before death
- Ex - broken bones, prosthetics, etc.
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Perimortem trauma
at or around the time of death
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Postmortem trauma
- after death
- Ex - animal marks, etc.
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Questions You Have to Ask
- 1. Is it bone?
- 2. If it is bone, is it human?
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What is the closest thing you will ever see to a human hand?
Forepaw of a bear
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LA Coroner System
- Not a medical examiner system
- Elected position
- Main job - mental health & unattended deaths
- Typically medical doctors; only a few are pathologists
- May not perform autopsies - hire forensic pathologists
- If a medical doctor does not run, any citizen can
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Chief Medical Examiner
- Typically a board-certified forensic pathologist (medical school plus advanced training)
- May have pathologists working for him/her
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Pathologists
- Perform autopsies
- Can determine if death is from accident, suicide, homicide, natural causes, or is unknown (indeterminate)
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Attended death
- Under care of physician
- Extended illness
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Unattended death
- Unexpected
- Perhaps result of trauma
- No physician present to render opinion
- Accidents, homicides, sudden illness
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Skull Layers
- Like a sandwich - outer layer, middle layer, inner layer
- Called tables
- Diploe: middle layer; spongy bone in between outer and inner layers
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Positions of the Skull
- Superior: top
- Anterior/Ventral: front
- Posterior/Dorsal: back
- Inferior: bottom
- Lateral: side
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Fontanelles
- Wide open
- Malleable plates to allow for brain growth
- Bregmatic
- "Soft spot"
- Last fontanelle closes between 20-24 mos
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Sutures
- Skull joints
- Most are interlocking (except squamousal - bevel)
- Fuse at different times in our lives
- Wide open at birth
- Typically all closed by 35 yrs
- Misleading in terms of determining age
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Extra bones
Wormian (Native American)
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How many bones are in the human skull?
27 if you count the hyoid
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Shrunken skulls
- You cannot shrink a skull... but you can shrink a head
- No skull... soft tissue has been shrunken
- Jivaro skull
- War trophy
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Skull
cranium + lower jaw
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Cranium
- Everything on the skull except mandible
- Face, top (calotte), back, posterior, inferior portion
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Occipital condyles
points of articulation with post-cranial skeleton
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Post-cranial skeleton
Any bone inferior to the skull
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How many vertebra are in the vertebral column?
- 24 vertebra
- 7 cervical vertebra (lack foramen)
- 12 thoracic vertebra (articulate with ribs)
- 5 lumbar vertebra
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How many bones in the human hand?
27
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How many bones in the human foot?
26
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Insect Activity as a Force that Promotes Decay
- Flies don't lay eggs in the rain
- Generally insects (typically secondary screw worms) lay eggs within minutes at temperatures above 50F
- Insects will not lay eggs at colder temperatures
- Eggs hatch within 8-18 hrs of insect access to the remains
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Air Decomposition vs. Water Decomposition
- Generally speaking, bodies decompose in air twice as fast as in water.
- CLIMATE PLAYS A MAJOR ROLE IN DECOMPOSITION
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Death Time Clock - Gloving
- Epidermis sloughs/peels off
- Fingerprints on outer skin
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Factors that play a role in postmortem decomposition in water
- Environment: temperature, depth, current, marine life, obstructions/debris
- Body: clothing, submerged vs. floating, type of joint, position of joint, amount of surrounding tissue, trauma
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Lacey Peterson Case
- Mother & baby; husband convicted of killing them
- Baby washed ashore; only part of mother found
- Gases in body expelled the baby after the mother was dead
- In water, 50F or below, bacterial breakdown is retarded
- Also retarded by salinity of water (salt content)
- Body will surface when putrefaction makes it bouyant
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Determining Sex from a Skull: Chin
- Male - square
- Female - rounded/pointed
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Determining Sex from a Skull: Mastoid Process
- Male - large
- Female - small
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Determining Sex from a Skull: External Occipital Protuberance
- Male - large
- Female - poorly developed
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Determining Sex from a Skull: Forehead
- Male - retreating
- Female - vertical; biparietal bossing (spreading/flare of parietal bones)
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Determining Sex from a Skull: Orbital Margin
- Male - rounded
- Female - sharp
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Determining Sex from a Skull: Supraorbital Ridge
- Male - prominent
- Female - absent or small (gracile)
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Determining Sex from a Skull: Muscle lines
- Male - prominent
- Female - poorly developed
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Determining Sex from a Skull: Ascending Ramus of Mandible
- Gonion
- Male - close to 90° angle
- Female - obtuse angle
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Determining Sex from a Skull: Root of Zygoma
- Male - extends beyond auditory meatus
- Female - does not extend beyond auditory meatus
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Sexual Dimorphism
difference in features (usually size) between sexes
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Tools to Measure Bones
- Calipers
- Sliding calipers - calibrated in mm & cm; used on the skull
- Spreading calipers
- Osteometric board - measures long bones to determine height
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What is the best bone in the body for determining sex?
hip bone (innominate)
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Fordisc
Software package used to determine whether skull measurements indicate sex (male or female)
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parts of the pelvis
- right innominate
- left innominate
- sacrum
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obturator foramen
- oval in males
- triangular in females
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pubic symphysis
where the pubis bones fuse
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sacro-iliac joint
where sacrum and hip bones fuse; changes throughout lifetime
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greater sciatic notch
- narrow in males
- wide in females
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Phenice method
- Female pubic bone is longer than a male's - continues to grow
- Region directly below pubic bone will be concave in females
- Pubic bone on inferior border of male hip bone will be convex
- Subpubic area (medial aspect of the ischiopubic ramus) is wider in a male than it is in a female
- Females have very broad muscle attachment line (rough) called the ventral arc that appears after 25 years of age
- Males do not have a ventral arch
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